Note: Descriptions are shown in the official language in which they were submitted.
l. 1228000
CHROMIUM APPEARANCE PASS IVATE SOLUTION
AND PROCESS
The present invention relates to ~assivation of
metal surfaces to impart the apPearance of a chromium
passivate.
A variety of chromium containing aqueous
5. solutions have heretofore been used or proposed for
treating zinc, zinc alloy, cadmium, cadmium alloy and
aluminium surfaces for improving the corrosion resistance
properties thereof and to further enhance the appearance
of such surfaces by imparting a yellow or a blue-bright
10. coating thereto, the latter simulatiny a chromium
finish. Su~h treating solutions originally contained
chromium in the hexavalent state and in more recent
years the chromium constituent was present as a mixture
of the hexavalent and trivalent forms. The reduced
15. toxicity of trivalent chromium and the increased
simplicity and efficiency in treating waste effluents
containing trivalent chromium has occasioned an i~lcreased
commercial use of passivate solutio~s in which the
chromium constituent is substantially entirely in the
20. trival~nt state. Such prior trivalent chromium passiv-
ating solutions have been found to be somewhat less
effective than the traditional hexavalent chromium
passivating solutions in imparting good corrosion
resistance to zinc and zinc alloy, cadmium, cadmium
25. alloy, and aluminium, aluminium alloy, magneslum and
magnesium alloys surfaces and there has, accordingly,
been a contlnuing need for further improvement in
trivalent chromium passivating solutions and processes.
The excellent corrosion protection provided by
30. hexavalent chromium passivating solutions is generally
associated with a light yellow iridescent passlvate
,~ ,
t-
film which has been recognised and embodied in ASTM
specifications. Conventionally, trivalent chromium
passivate films are of a clear to light-blue colour
and are of inferior corrosion protection than the
5. yellow hexavalent passivate film. This problem has
been further aggravated by a conversion from convent-
ional cyanide zinc and cadmium plating ~rocesses to
acid and alkaline non-cyanide eIectroplating baths
which ~roduce metal deposits which are not as -
10. receptive to chromium passivate treatments.
Ty~ical of ~rior art com~ositions and ~rocessesfor treating metal surfaces are those disclosed in
United States Patents Numbers 2,393,663; 2,559,878;
3,090,710; 3,553,034; 3,755,018; 3,795,549; 3,880,772,
15. 3,932,198; 4,126r490; 4,171,231; British Patent Numbers
586,517 and 1,461,244; and German Patent No 2,526,832.
122~00~
According to its broadest as~ect the ~resent
invention provides an aqueous acidic solution useful in
the treatment of receptive metal substrates to imPart
a passivate film thereon comprising
5. A~ hydrogen ions to provide an acidic pH;
B) an oxidizing agent: and
~) at least one or iron, cobalt, nickel,molybdenu~,
manganese, aluminium, lanthanum, lanthanide mixture or
cerium ions or mixtures thereof in an amount effective
10. to impart increased corrosion resistance to the treated
substrate.
The present invention is particularly applicable
but not limited to the treatment of alkaline and acidic
non-cyanide zinc and cadmium electrodeposits to impart
15. improved corrosion resistance thereto. Particul~rlv
satisfactory results are obtained on decorative zinc
and cadmium electrodeposits of the bright and semi-bright
types although beneficial effec~s are also achteved on
zinc and zinc alloy substrates such as galvanized
20. substrates, zinc die castings and substrates comnrised
of cadmium or alloys of cadmium predominantly com~rised
of cadmium. While the invention in its various asnects
as herein described is particularly dlrected to the
treatment of zLnc and zinc alloy surfaces, it has been
25. observed that beneficial results are also obtained in
the treatment of aluminium, aluminium alloy, maqnesium
and magnesium alloy surfaces to orm a passivate ellm
or coating thereon. ~ccordingly, the present inventlon
ln lts broad sense is directed to the treatment of metal
30. surfaces which are receptive to the formatlon of a
passivate film thereon when contacted wlth the solution
~22800~)
of the present invention in accordance with the process
parameters disclosed.
In accordance with the process aspects of the
present invention, zinc, cadmium, zinc alloy, cadmium
5. alloy, aluminium and magnesium surfaces are contacted
with the aqueous acidic treating solution, at a tem~er-
ature ranging from about 40 up to about 150~ ( 4
to 66C) for a period of time typically ranging from
about 10 seconds up to about 1 minute to form the
10. desired passivate film.
A treating bath formulation in-accordance with
the various aspects of the present invention which are
described in detail below may be applied to a substrate
to be treated by spray, immersion, flooding or thellike
15. for a period of time sufficient to form the desired
passivate film thereon. The treating solution is
controlled within a temperature range of about ~0 to
about 150F ( 4 to 66C), with a temperature range
of about 70 to about 90F ( 21to 32C) being ~ref~rred.
20. Temperatures above about 90F ( 32C) have a tendency
to cause a rapid loss of the peroxide-type oxidizing
agents when used whereas temperatures below about 70F
( 21 C) reduce the activity of the bath requiring
lncreased contact times to achieve a passivate fllm of
25. the same ~hickness or colour intensity as can be achieved
at the hlgher temperatures at short time intervals.
Typically, contact times of about 20 or 30 seconds to
about 1 minute are satlsfactorily with contact times of
about 30 seconds b~ing usually preferred.
30. According to a first aspect of the present invention
12~8~)0~
there is provided a passivating solution which does not
contain any chromium ions and is effective for imparting
corrosion resistance to zinc, cadmium and aluminium
surfaces as well as alloys thereof.
5. This aspect of the present invention provides a
treating solution and process which is effective ~o
selectively impart a clear blue-bright or a clear light-
yellow passivate film to zinc, zinc alloy, cadmium,
- cadmium alloy, aluminium and magnesium surfaces which
10. provides for improved corrosion resistance. The present
invention is further characterized by a process which
is simple to control and operate and which is of efficient
and economical operation.
The benefits and advantages of the first ~qpect
15. of the present invention are achieved in accorda~ce with
the composition aspects thereof by providing an aqueous
acidic treating solution containing as its esssential
constituents hydrogen ions preferably to provide a
solution pH of about 1.2 to about 2.5 which can be
20. conveniently introduced by mine.al acids such as sulphuric
acid, nitric acid or hydrochloric acid; an oxidizlng
agent of which hydrogen peroxide itself is preferred,
preferably present in an amount of about 1 to about 20
g/l, iron and cobalt ions in an amount effective to
25. impart increased corrosion resistance to the treated
substrate and preferably present ln an amount of about
0.02 to about 1 g/l to form a blue-bright or clear
passivate film.
The treatlng solution contains an oxidizlng agent
30. in an amount effective to activate the metal surface and
1~:28~0()
to form a passivate film thereon, and iron and cobalt
ions present in an amount effective to activate the
bath and to impart integral initial hardness to the
passivate film. The treating solution may optionally
5. further co~tain cerium ions present in an amount
effective to further activate the bath and to promote
the formation of a clear light-yeIlow passivate film.
Additionally, the treating solution may optionally
contain halide ions including fluoride, chloride and
10. bromide ions for increasing the hardness of the passivate
film as well as one or more compatible wetting agents
preferably in a small amount for achieving efficient
contact with the substrate being treated.
The iron and cobalt ions are conveniently
15. introduced into the bath by way of bath soluble and
compatible salts including sulphates~ nitrates, or
halide salts. The concentration of the combined iron
and cobalt ions to achieve appropriate actlvation of
the treating bath is controlled within a range of about
20. 0.02 to about l g/l, preferablv within a range of about
0.1 to about 0.2 g/l. The iron and cobalt ions individ-
ually are present in an amount of about 0.01 to about
0.5 g/l with individual amounts of about 0.05 to about
0.1 g/l being preferred.
25. When a passivate film is desired having a light-
yellow appearance, the treating bath furthex contains
cerium ions present in an amount effectlve to further
activate the bath and to impart a clear yellowish colour,
preferably an iridescent light-yellow colour to the
30. passivate film on the substrate treated. The cerium
ions can be introduced in the form of any bath soluble
122~3~)0~)
and compatible cerium salt including cerium sulphate
(Ce(SO~)2 4H20); halide salts such as cerous chloride
(CeC13 6H20~; or nitrate salts such as cerium nitrate
(Ce(N03) 5H20), (Ce(N03)3(OH) 3H20). Usually, at
5. least some of the cerium ions are introduced into the
bath in ~he tetravalent state to impart the character-
istic yellow colour of the tetravalent cerium ion into
the passivate film. Certain oxidizing agents such as
hydrogen peroxide, act as a reducing agent under the
10. acid conditions prevalent in the bulk of the operatin~
bath and reduce some of the tetravalent cerium ions
to the trivalent state. However, oxidizing agents such
as hydrogen peroxide revert from a reducing agent to
an oxidizing agent at the interface of the substrate
15. being treated due to the higher pH prevalent at the
interface and oxidize at least some of the ~ivalent
cerium ions to the tet~avalent scate which are de~osited
in the film and impart the characteristic yellow colour
thereto. When using such oxidizing agents as
20. hydrogen veroxide, accordingly, all of the cerium ions
can, if desixed, be initially introduced into the
operating bath in the trivalent state of which a portion
are oxidized to the tetravalent state at the interface
of the substrate. The passivate film usually contains
25. a mixture of trivalent and tetravalent cerium compounds
and the intensity of the yellow colour of ~he film is
dictated by the concentratlon of the tetravalent cerium
compounds present. The cerium lons in addition to
imparting a light-yellow colour to the passivate fllm
30. also improve the corrosion resistance of the treated
122800~
substrate. The cerium sulphate comDound, due to solub-
ility difficulties, is ~referablY added to the bath in
the form of an acid solution such as à dilute sulphuric
acid solution containing the cerium sulphate dissolved
5- therein.
The concentration of cerium ions in the operating
bath can range from about 0.5 up to about 10 g/l with
concentrations of from about 1.0 to about 4.0 g/l
being preferred. The concentration of cerium ions is
10. in part influenced by the magnitude of the yellow
coating desired and higher concentrations of the cerium
ions produce corresponding increases in the yellow
colour of the passivate film.
Because o~ cost co~siderations, the cerium ions
15 n are preferably introduced as a commercially avai~able
mixture of rare earth salts of metals in the lanthanide
series which contains cerium compounds as the prlncipal
component. One such commercially avallable material
is a cerous chloride solution containing about 4~%
20- solids of which CeC13-6H20 predominates. The cerous
chloride solution is derlved from rare earth oxide (REO)
concentrate sold by Molycorp, ~nc. of White Plains,
New York under product code 5310 containing a minimum
of 99 percent total REO of which CeO2 is 96~, I.a203 is
25- 2.7%, Nd203 is 1% and Pr60 1 is 0.3%. A ceric sulphate
solution is commercially available from the same source
containing about 42% solids of which Ce(S04)2.H20
predominates and which is also prepared from product
code 5310 containing other rare earth metal compounds
in similar minor amounts.
122800~
The operating bath in accor~ance with this first
aspect of the present invention can conveniently be
prepared by employing a concentrate containing the
active constituents with the exception of the cerium
5. ions and oxidizing agent which is ada~ted to be diluted
with water t~ which the cerium ions, i.f employed, and
oxidizing agent are separately added to form a bath
containing the constituents within the desired concen-
tration range. Similarly, replenishment of the bath
10. on a continuous or intermittent basis can be achieved
employing a concentrate of the active constituents
with the exception of the cerium ions and oxidizing
agent which are individually added separately to the
operating bath. Typically a bath make--up concentrate
15. can conta.in from about 0~5 to ahout 50 g/l of iron and
cobalt i.OilS, halide ions up to about 20 g/l and a
suitable surfaetant :In an amo~t up to about S g/l
if employed. Such a make~up concentrate .is adapted
to be diluted with about 96 volume percent water -to
20. which cerium ions, if employed, and a.n oxidizing agent
are added to produce an operating bath containing the
active constituents within the ranges specified. The
oxidlzing agent such as hydrogen peroxide, for example,
is separately introduced into the bath preferabl~ in a
~5. form commercially available containing from about 35
to 40 percent by volume hydro~en ~eroxlde.
As previously advised, ~he lo~ solublllty of
cerlum sulphate makes it deslrable to lntroduce this
constituent into the operating bath ln the orm of an
30. aqueous acidic solution. Normally, the use of cerium.
~2~300~
1.0
sulphate in the high concentrations necessary to form
a concentrate with the remaining active constituents
other than the peroxide constituent causes precipit-
ation of the ceri um compound. Even when the cerium
i.s introduced as a halide or nitrate salt, the pre-
sence of sulphate ions in the concentrate employed
introduced by the other constituents causes
precipi.tation .
Accordin~ly, the cerium concentrate is pre-
ferably formed as a separate addition cornponent and
may comprise aqueous acidic solutions of cerous
chloride or ceric sulphate having a cerium ion
concentration of from about 200 to about 320 g/l and
about 60 to 100 g/l, respectively. Such cerium
concentrates may conveniently by comprised of the
commercially available materials hereinbefore
described available from Molycorp, Inc.
The treat inq bath contains hydrogen ions pre-
ferably in an amount to provi.de a pH of about 1. . 2
to about 2 . 5 with a pH range of about 1. 5 to about
2.0 being preferred. Ac~dification of the operating
bath ~o within the desired ph range can be achieved
by a variety of mineral acids and organic acids such
as sulphuric acid, nitric acid, hydrochloric acid,
formic acid, acetic acid, or propionic acid of which
sulphuric acid and nitric acid are preferred. The
presence of sul.phate ions in the bath has been fourld
beneficial in ach.ievirl(3 tlle dcsirecl p~.issiv.ltion o~'
trle ~ub~.l rat~ c~ l c~lrl t~ rlt.r~ c.;l) lp~ r i~
acid ad.litioll or sulE)llat:(! 3alt~ Oe the o~:ller bcith
constituents. Sulphate .ion collcelltrations can ranqt.?
in amounts up to l5 cl/l wi th conc(?ntra~iol)s of from
about. 0.5 to about 5 ~/1 being prc?ferrt;?d~
.i~
~2Zc13000
11
The treating bath fur-the~ contains an oxidiz-
ing agent or agents which are bath compatible of
which peroxides including hydrogen peroxide and
metal peroxides such as the al~ali metal peroxides
s are preferred. Hydrogen peroxide itself of a
commercial grade containing about 25% to about 60~
by volume peroxide constitutes the preferred material.
Other peroxides that can be employed include zinc
peroxide. Additionally, ammonium and alkali metal
persulphates have also been found effective as
oxidizing agents~
The concentration of the oxidizing agent or
mixture of oxidizing agents is controlled to achieve
the desired surface appearance of the treated
substrate. Typically, the concentration of the
oxidizing agent can range from about 1 to about
20 g/l with an amount of about 3 to about 7 9/1
being preferred, calculated on a weight equivalent
effectiveness basis to hydrogen peroxide.
As an optional but preferred constituent, the
bath may contain halide ions including chlorine,
bromine and fluorine ions which have been found to
enhance the hardness of the passivate film on the
treated subs~-rate.The halide ions or mixtures thereof
can conveniently be introduced employing any of the
alkali metal and ammonium salts thereof as well as
salts of the metal ions hereinabove set forth. The
concentration of the total halide constituent in the
bath normally may ran~e up to about 8 gram~ per
litre with concentrations of abollt 0.1 to about
2.5 g/l being kypical.
In the second fourth and fifth aspects of the
invention it may be preferred that the concentration
of the total halide constituent in the bath normally
range up to about 2 grams per litre with concentra-
tions of about 0.1 to about 0.5 g/l being typlcal.
12 ~ 22 8 00 ~
In addition to the foregoing, the use of a
small effective amount of a variety of bath compatible
wetting agents also provides beneficial results in the
nature of the passivate film deposited. When employed,
the wetting agent can be present in concentrations up
to about 1 g/l with concentrations of about 50 to about
100 mg/l being preferred.
Wetting agents suitable for use in the treating
bath include aliphatic fluorocarbon sulphonates avail-
able from 3M under the trademark FLUORAD, such as, forexample, FLUORAD FC 98, which is a non-foaming wetting
agent and its use at about 100 mg/l in the working bath
improves the colour and hardness of the passivate film.
A second class of suita~le wetting agents is the sulpho-
derivatives of succinates. An example of this class isAEROSOL MA-80 (trade mark) which is dihexyl ester of
sodium sulphosuccinic acid and is commercially available
from American Cyanamid Company. A third class of suit-
able wetting agents is the sulphonates of naphthalene
which are linear alkyl naphthalene sulphonates, such as
PETRO BA (trade mark), for example, available from
Petrochemical Company.
According to the gecond aspect of the present
invention there is provided a treating solution and
process which is effective to impart improved corrosion
resistance to zinc, zinc alloy, cadmium and cadmium
alloy, as well as aluminium and magnesium surfaces and
to impart a desirable surface finish which can range
from a clear bright to a light blue-bright appearance,
which procegs is simple to control and operate and which
is of efficient and economical operation. This and the
13 12 ~ ~0 ~
third to seventh aspects of the invention all utilize
trivalent chromium ions.
The benefits and advantages of the second
aspect of the present invention are achieved in
accordance with the composition aspects thereof by
providing an aqueous acidic treating solution con-
taining as its essential constituents, chromium ions
substantially all of which are present in the tri-
valent state preferably at a concentration of from
about 0.05 grams per litre (g/l) up to saturation,
hydrogen ions preferably to provide a solution pH
of about 1.5 to about 2.2 which can be conveniently
introduced by mineral acids such as sulphuric acid,
nitric acid or hydrochloric acid, an oxidizing agent
of which hydrogen peroxide itself is preferred, pre-
ferably present in an amount of about 1 to about
20 g/l, and iron ions preferably present in an
amount of about 0.05 to about O.S g/l e.g. in the
ferric state in further combination with at least
one additional metal ion selected from the group
consisting of cobalt, nickel, molybdenum, manganese,
lanthanum, lanthanide mixture and mixtures thereof
present in an amount effective to impart increased
corrosion resistance to the treated substrate and
to activate the bath and the formation of a
chromium passivate film on the substrate treated.
As mentioned for the first aspect of the invention
the solution may Purther optionally contain halide
ions for impartin~ Initial hardness to t.hl? CO~lt: in~,
as well as a wetting ac~ent.
In the second aspect o~ the invention
whilst it is applicable in the same way as the
first aspect, in the case of decorative zinc
electroplatings, a further
i22a~0~
14.
enhancement of the appearance of such substrates in
addition to the corrosion resistance imparted is
achieved by the passivate film which ranges from a
clear bright to a light blue-bright appearance simu-
lating that of a chromium deposit.
The treating solution contains an oxidizing
agent in an amount effective to activate the hydrated
trivalent chromium to form a chromate film on the
metal surface, iron ions present in the operating bath
in the ferric state at a concentration ranging from
about 0.05 to about 0.5 grams per litre and at least
one additional metal ion selected from the group con-
sisting of cabalt, nickel, molybdenum, manganese,
lanthanum and mixtures thereof present in an amount
effective to impart integral initial hardness to the
gelatinous chromate film.
The trivalent chromium ions can be introduced
in the form of any bath soluble and compatible salt
such as chromium sulphate (Cr2(S04)2), chromium alum
(KCr(SO4)2), chromium chloride (CrC13), chromium
bromide (CrBr3), chromium fluoride (CrF3), or chromium
nitrate (CrN03). The trivalent chromium ions can also
be introduced by a reduction of a solution containing
hexavalent chromium ions employing an appropriate re-
ducing agent of any of the types well known in the artto effect a substantially complete stoichiometric
reduction of all of the hexavalent chromium to the
trivalent 8tate.
The concentration of the trivalent chromium
ions in the treating solution may range from as low as
about 0.05 g/l up to saturation with quantities of
about 0.2 to 2 g/l being preferred. Typically, the
8~00
15.
operating bath contains from about 0.5 to about 1 g/l
trivalent chromium ions.
The treating solution further contains iron
ions preferably present in an amount of about 0.05
to about 0.5 g/l with concentrations ranging from about
0.1 to about 0.2 g/l being preferred. The iron ions
in the operating bath are predominantly in the ferric
state due to the presence of the bath oxidizing agents
although they can be added in the ferrous form. As in
the case of the chromium ions, the iron ions can be
added to the bath in the form of any bath soluble and
compatible iron salt such as ferrous ammonium sulphate,
ferric sulphate, ferric nitrate, or iron halide salts.
Of the foregoing, ferric sulphate comprises the pre-
ferred material for economic reasons and because theuse of this salt also introduces the desired sulphate
ions into the solution.
In addition to the iron ions, the bath further
contains at least one additional metal ion selected
from the group consisting of cobalt, nickel, molybdenum,
manganese, lanthanum, as well as mixtures thereof. The
foregoing metal ions or mixtures of metal ions are
conveniently introduced as in the case of the iron ions,
by way of bath soluble and compatible metal salts
including the sulphates, nitrates or halide salts. For
economic reasons, the lanthanum ions are preferably
introduced not as a pure lanthanum compound, hut a~ a
mixture of the rare earth salts of the metals of the
lanthanide serie~, thereinafter designated as
- 12Z8000
16.
"l~nthanide mixture") which contains lanthanum compounds
- as the predominant constituent. A commercially avai-
lable lanthanide mixture which is suitable for use in
the practice of the present invention is Lanthanum-
Rare Earth Chloride, product code 5240, available from
Molycorp, Inc. of White Plains, New York. This
product has the general formula La-REG13-6H20 and is
available as a solution containing about 55 to 60% by
weight solids. The solution is prepared from a rare
earth oxide (RE0) concentrate containing a minimum of
46% by weight to~al RE0 comprising about 6~ lanthanum
oxide (La203), 21.5% neodymium oxide (Nd203), 1~
cerium oxide (CeO2), 7.5% praseodymium oxide (Pr6011)
and 1% of residual RE0.
The presence of such other rare earth metals in
the solution dies not appear to have any adverse effect
at the low concentrations in which they are present and
may further contribute to the activation of the treating
solution in forming the pas3ivate film.
The concentration of the additional metal ions
for appropriate activation of the treating bath is
controlled to provide a concentration ranging from
about 0.02 up to about 1 g/l with concentration of
from about 0.1 to about 0.2 g/l being preferred.
The operating bath in accordance with this second
a~pect of the invention can conveniently be prepared by
employing a concentrate containing the active con~tl-
tuents with the exception of the oxidizing agent which
is adapted to ~e diluted w$th wat0r to form a bath con-
taining the con~tituents within the de~ired concentra-
tion range.
o
17
Similarly, replenishment of the bath on a continuous
or intermittent basis can be achieved employing a
concentrate of the active constituents with the
exception of the oxidizing agent which is added
separately to the operating bath. Typically, a bath
make-up concentrate can contain from about 10 to
about 30 g/l chromium ions, about 0.5 to about lO g/l
iron ions, from about 5 to about 50 g/l of at least
one additional metal ion of the group consisting of
cobalt, nickel, molybdenum, manganese, lanthanum,
lanthanide mixture or mixtures thereof, halide icns
up to about 20 g/l and a suitable surfactant in an
amount up to about 5 g/l if employed. Such a make-up
concentrate is adapted to be diluted with about
98.5 volume percent water to produce an operating
bath containing the active constituents within the
ranges specified. The oxidizing agent such as
hydrogen peroxide, for example, is separately
introduced into the bath preferably in a form
commercially available containing from about 35 to
40 percent by volume hydrogen peroxide.
According to the third aspect of the present
invention there is provided a treating solution and
process which is effective to impart a clear light-
yellow passivate film to zinc, zinc alloy, cadmium,cadmium alloy, aluminium and magnesium surfaces
which provides for improved corrosion resistance
approaching or comparable to that heretofore
obtained employing eonventional hexav-~Ient chromiutn
passivating solutions. The present invention is
further characterized by a process which is sitnple
to control and operate and which is of efficient
and economical operation.
'~-
12~300~)
18.
The benefits and advantages of the third aspect
of the present invention are achieved in accordance
with the composition aspects thereof by providing an
aqueous acidic treating solution containing as its
essential constituents, chromium ions substantially
all of which are present in the trivalent state prefer-
able at a concentration of from about 0.05 grams per
litre (g/l) up to saturation, hydrogen ions preferably
to provide a solution pH of about 1.2 to about 2.5
which can be conveniently introduced by mineral acids
such as sulphuric acid, nitric acid, or hydrochloric
acid, an oxidizing agent of which hydrogen peroxide
itself is preferred, preferably present in an amount of
about 1 to about 20 g/l, and cerium ions present in an
amount effective to activate the bath and the formation
of a clear light-yellow chromium passivate film on the
treated substrate.
In addition to the cerium ions in the treating
solution, the solution may optionally and preferably
further contain an additional metal ion selected from
the group consisting of iron, cobalt, nickel, moly-
bdenum, manganese, lanthanum, lanthanide mixtures as
well as mixtures thereof to provide a further activation
of the bath and passivate film formation. As mentioned
2~ for the earlier aspects of the invention the solution
may optionally also contain halide ion~ for imparting
harrdness to the coating in addition to a small amount
of a w~tting agent. The cerium ions can be introduced
with the treating solution in thi~ third aspect of the
invention in the same manner as described for the first
t
- ~228!~0~
19 .
aspect of the invention.
In addition to the cerium ions, the bath may
further optionally and preferably contain at least one
additional metal ion selected from the group consisting
of iron, cobalt, nickel, molybdenum, manganese, lan-
thanum, lanthanide mixtures as well as mixtures thereof.
Such metal ions may be introduced into the treating
solution in this third aspect of the invention in the
same manner as already described for the second aspect.
The operating bath in accordance with this third
aspect of the invention can conveniently be prepared
by employing a concentrate containing the active
constituents with the exception of the cerium ions and
oxidizing agent which is adapted to be diluted with
water to which the cerium ions and oxidizing agent are
separately added to form a bath containing the cons-
tituents within the desired concentration range.
Similarly, replenishment of the bath on a continuous or
intermittent basis can be achieved employing a concen-
trate of the active constituents with the excepticn ofthe cerium ions and oxidizing agent which are indivi-
dually added separately to the operating bath. Typically
a bath make-up concentrate can contain from about 10
to about 80 g/l chromium ions, from about 0.5 to about
50 g/l of additional metal ions of the group consisting
of iron, cobalt, nickel, molybdenum, mangane~e, lanthanum,
lanthanide mixture, or mixtures thereof, halide ions up
to about 20 g/l and a suitable ~ur~actant ln an amount
up to about 5 g/l i~ employed. Such a maXe-up concen-
trate is adapted to be diluted with about 96 volumepercent water to which cerium ions and an oxidizing
o~
20.
agent are added to produce an operating bath containing
the active constituents within the ranges specified.
The oxidizing agent such as hydrogen peroxide, for
example, is separately introduced into the bath prefer-
able in a form ccmmercially available containing fromabout 35 to 40 percent by volume hydrogen peroxide.
As previously advised, the low solubility of
cerium sulphate makes it desirable to introduce this
constituent into the operation bath in the form of an
aqueous acidic solution. Normally, the use of cerium
sulphate in the high concentrations necessary to form
a concentrate with the remaining active constituents
other than the peroxide constituent causes precipitation
of the cerium compound. Even when the cerium is intro-
duced as a halide or nitrate salt, the presence of~ulphate ion~ in the concentrate employed introduced
by the other constituents causes precipitation.
Accordingly, the cerium concentrate is preferably formed
as a separate addition component and may comprise
aqueous acidic solutions of cerous chloride or ceric
sulphate hav.ing a cerium ion concentration of from about
200 to about 320 g/l and about 60 to 100 g/l, respec-
tively. Such cerium concentrates may conveniently be
comprised of the commercially available materials
hereinbefore-described available from Molycorp, Inc.
According to the fourth aspect of the present
invention there is provided a treating solution and
process which is effective to impart improved corrosion
resistance to zinc, zinc alloy, cadmium and cadmium
alloy, as well a~ aluminium and magnesium surfaces and
to impart a decirable surface finish which can range
from a clear bright to a light blue-bright to a yellow
iridescent appearance, which produces a passivate film
~2;~300~
21.
of improved clarity and initial hardness, which process
is simple to control and operate and which is of effi-
cient and economical operation.
The benefits and advantages of the fourth aspect
of the present invention are achieved in accordance
with the composition aspects thereof by providing an
aqueous acidic treating solution containing as its
essential constituents, chromium ions substantially
all of which are present in the trivalent state
preferably at a concentration of from about 0.05 grams
per litre (g/l) up to saturation, (and which can be
introduced as discussed for the second and third
aspects), hydrogen ions preferably to'provide a solution
pH of about 1.2 to about 2.5 which can be conveniently
introduced by mineral acids such as sulphuric acid,
nitric acid, or hydrochloric acid, an oxidizing agent
of which hydrogen peroxide itself i5 preferred, prefer-
able present in an amount of about 1 to about 20 g/l,
a bath soluble and compatible organic carboxylic acid
present in an amount effective to impart initial
hardness and clarity to the passivate film, the said
organic acid having the structural formula:
(OH)a R (C~)b
Wherein:
a is an integer from 0 to 6,
b is an integer from 1 to 3, and
R represents an alkyl, alkenyl, or aryl group
containing from Cl to C6 carbon atoms,
as well as the bath soluble and compatible salts
thereof, and at least one additional metal ion selected
! ;~
22. 122800~
from the group consisting of iron, cobalt, nickel,
molybdenum, manganese, lanthanum, cerium and
lanthanide mixtures, as well as mixtures thereof present
in an amount effective to activate the bath and forma-
tion of a chromium passivate film of the desiredappearance on the substrate treated desirably imparting
initial hardness to the gelatinous chromate film. As
mentioned for the earlier aspects of the invention, the
solution may further optionally contain halide ions for
imparting additional hardness to the coating, as well
as a wetting agent. In this fourth aspect of the
invention whilst it is applicable in the same way as
the first aspect in the case of decorative zinc elec-
troplatings, a further enhancement of the appearance of
such substrates in addition to the corrosion resistance
imparted is achieved by the passivate film which ranges
from a clear bright to a light blue-bright appearance
simulating that of a chromium deposit or alternatively,
a clear light-yellow appearance simulating that obtained
by use of prior art hexavalent chromium solutions.
In addition, the bath further contains at least
one additional metal ion selected from the group
consisting or iron cobalt, nickel, molybdenum, manganese,
lanthanum, lanthanide mixtures and cerium, as well
as mixtures thereof. The foregoing metal ions or
mixtures of metal ions are conveniently introduced into
the bath by way of bath soluhle and compatible metal
salts including the sulphates, nitrates or halide salts,
as discussed for the second and third embodiments and
such materials as are discussed above for those aspects
- 1~2~3~0~)
23.
can be and desirably are used in this aspect of the
invention.
The concentration of the additional metal ions
other than cerium ions for appropriate activation of
the treating bath to produce a clear to blue-bright
appearance is controlled to provide a concentration
ranging from about 0.02 up to about 1 g/l with concen-
trations of from about 0.1 to about 0.2 g/l being pre-
ferred. While such metal ions can be used in concen-
trations above 1 g/l, such as up to 10 g/l, the use ofsuch higher concentrations even in the absence of cerium
ions tends to produce dull films of ayellow tint rather
than the desired clear or light-blue films. For this
reason, such higher concentrations are undesirable from
an appearance standpoint.
A further essential constituent of the improved
bath of the present invention comprises an organic
carboxylic acid or salt thereof of the structural for-
mula as hereinbefore set forth present in an amount
effective to impart increased clarity and initial
hardness to the gelatinous chromate film deposited.
The unexpected improvement in clarity of the film is
particularly pronounced in connection with the light-
yellow iridescent films produced from cerium ion con-
taining solutions. The particular concentration or rangeof concentrations of the clar;ty/hardness agent will
vary in proportion to molecular weight o~ the particular
acid and/or metal salt employed with higher concentrations
required for an equivalent effectiveness as the molecular
weight of the additive agent increa~es. The particular
- 122~
24.
concentration to achieve optimum clarification and
hardness is also dictated to some extent by the con-
centration of the other metal ions present in the bath
with higher concentrations being used as the metal ion
concentrations increase. Generally, the organic car-
boxylic acid additive agent or metal salts thereof
can be employed in amounts ranging from about 0.05 up
to ~bout 4.0 g/l with concentrations of about 0.1 to
about 1.0 g/l being usually preferred.
The additive can be introduced as the organic
acid itself or as any bath soluble and compatible
metal salt including the alkali metal salts, ammonium
salts and salts of the several additional metal ions
in the bath. ~or economic reasons, the organic acid
is usually introduced as an acid or as the sodium or
potassium salt thereof.
Within the scope of the strllctural formula as
hereinabove set forth, organic carboxylic acids which
have been found particularly suitable include malonic,
maleic, succinic, gluconi~, tartaric and citric acids,
of which succinic and or succinate salts have been
found particularly effective.
The operating bath in accordance with this
fourth aspect of the invention can conveniently be
prepared by employing a concentrate contai*ing the
active ingredients with the exception of the oxidizing
agent and cerium ions, i~ used, which is adapted to be
diluted with water to form a bath containing the cons-
tituents within the desired concentration range.
3~ Similarly, replenishment of the bath on a continuous
or intermittent basis can be achieved employing a
l2zsoon
concentrate of the active constituents with the exception
of the oxidizing agent and cerium ions, if used, which
is added separately to the operating bath. Typically,
a bath make-up concentrate can contain from about lO
to about 80 g/l chromium ions, from about 1.0 to about
80 g/l of the organic carboxylic acid and/or salt
additive agent, from about 5 to about 50 g/l of at
least one additional metal ion of the group consisting
of iron, cobalt, ~ickel, molybdenum, manganese, lantha-
num, lanthanide mixture or mixtures thereof, halideions up to about 5 g/l if employed. Such a make-up
concentrate is adapted to be diluted with about 98
volume percent water to produce an operating bath con-
taining the active constituents within the ran~es
specified. The oxidizing agent such as hydrogen peroxide
for example, is separately introduced into the bath
preferably in a form commercially available containing
from about 35 to 40 percent by volume hydrogen peroxide.
The cerium ions, when employed, are preferably introduced
in the form of an aqueous acid solution of cerous chlo-
ride or ceric sulphate having cerium ion concent~ation
of from about 200 to about 320 g/l and about ~0 to about
100 g/l, respectively. Such cerium concentrates may
be conveniently comprised of the commercially available
materials hereinbefore described available from
Molycorp, Inc.
According to the fifth aspect of the preqent
invention there is provided a treating solution which
aims to reduce the severity of a problem of loss of
oxidizing agent associated with p~ior art baths. Thus
while improvements have been made in trivalent chromium
~ ., ~
12~800~
26
passivate compositions and processes to produce
commercially acceptable passivate films, a continu-
ing problem associated with such operating baths
has been the relatively rapid loss of the peroxide-
type oxidizing agent, particularly hydrogen peroxide,which is present as a necessary bath constituent to
achieve acceptable passivate films. Such prior art
operating baths also undergo a relatively rapid rise
in pH necessitating careful control and addition of
acids to maintain the pH level within the optimum
opera-ting range. The progressive loss of the peroxide-
type oxidizing agent, particularly hydrogen peroxide,
is due in part to the presence of activating metal
ions present in the solution as well as contaminating
metal ions such as zinc or cadmium, for example,
introduced by dissolution of the metal from substrates
being treated which bend to catalyze a decomposition
of the peroxide oxidizing agent. The progressive
loss of the peroxide-type oxidizing agents occurs
not only during processing but also during standing
of the bath overnight and over weekends during
plant shutdown. Typically, a fresh operating bath
containing 3% by volume of a 35% solution of hydrogen
peroxide on standing overnight will lose about 0.1%
by volume per hour of the hydrogen peroxide oxidizing
agent while a used solution containing from about
2 to about 10 grams per litre of contaminating zinc
ions will experience a loss of hydrogen peroxide at
a rate as great as about 0.4% by volume per hour. It
will be apparent from the foregoing that careful
monitoring of the operating bath composition and
frequent replenishment of the peroxide oxidizing
agent is required to maintain optlmum bath efficiency
which is not only costly but also time consuming.
i2~3000
27
Thus this fifth aspect of the present inven-
tion aims to provide a treating solution and process
which is effective to impart improved corrosion re-
sistance to zinc, zinc alloy, cadmium and cadmium
alloy, as well as aluminium and magnesium surfaces
and to impart a desirable surface finish which can
range from a clear bright to a light blue-bright to
a yellow iridescent appearance, which produces a
passivate film of improved corrosion resistance,
hardness, durability, clarity and initial hardness,
which provides a treating solution that is stabilized
against rapid loss of the peroxide oxidizing agent
and against a rapid rise in pH, which process is
simple to control and operate and which is of
efficient and economical operation.
The benefits and advantages of the fifth
aspect od the present invention are achieved in
accordance with the composition aspects thereof by
providing an aqueous acidic treating solution con-
taining as its essential constituents, chromiumions substantially all of which are present in the
trivalent state preferably at a concentration of
from about 0.05 grams per litre (g/l) up to satura-
tion (and which can be introduced as discussed for
the second to fourth aspects), hydrogen ions pre-
ferably to provide a solution pH of about 1.2 to
about 2.5 which can be conveniently introduced by
mineral acids such as sulphuric acid, nitric acid,
hydrochloric acid or the like, an oxidizing agent
of which hydrogen peroxide itself is preferred, pre-
ferably present in an amount of about 1 to about
20 g/1, a stabilizing additive comprising a mixture
of l-hydroxy ethylidene-l,l diphosphonic acid and
1~28~)0n
28
citric acid and the bath compatible and soluble
salts thereof present in an amount effective to re-
duce loss of the peroxide oxidizing agent and to
stabilize the pH of the operating bath, and at least
one additional metal ion selected from ~he group
consisting of iron, cobalt, nickel, molybdenum,
manganese, aluminium, lanthanum, lanthanide mixtures,
and cerium as well as mixtures thereof present in
an amount effective to activate the bath and forma-
tion of a chromium passivate film of the desiredappearance on the substrate treated. As mentioned
for the earlier aspects of the invention the solu-
tion may optionally contain halide ions for imparting
additional hardness to the coating, and optionally,
a wetting agent. It may also incorporate a bath
soluble and compatible silicate compound present in
an amount effective to impart increased corrosion
resistance and hardness to the passivate film e.g. in
an amount of about 0.01 to about 5 g/l calculated
as SiO2 as discussed in connection with the sixth
aspect below. It may also incorporate a bath soluble
compatible organic carboxylic acid present in an
amount effective to further impart initial hardness
and clarity to the passivate film as discussed in
connection with the fourth aspect above.
In this fifth aspect of the invention whilst
it is applicable in the same way as the first aspect
in the case of decorative zinc electroplatings, a
further enhancement of the appearance of such
substrates in addition to the corrosion resistance
imparted is achieved by the passivate film which
ranges from a clear bright to
~'
.~,
1%;~800~
29.
a light blue-bright appearance simulating that of a
chromium deposit or alternatively, a clear light-
yellow appearance simulating that obtained by use of
prior art hexavalent chromium solutions.
A further essential constituent of the treating
bath in accordance with the fifth aspect of the
invention is the stabilizing agent comprising a
mLxture of l-hydroxy ethylidene-l,1 diphosphonic acid
and citric acid as well as the bath soluble and com-
1~ patible salts thereof. The combination of the
diphosphonic and citric acid constituents appears to
provide a synergistic action in not only reducing the
deco~position and rate of loss of the peroxide-type
oxidizing agent but also in stabilizing the pH of the
operating bath preventing a rapid rise as had here-
tofore been experienced in prior art-type trivalent
chromium passivation treating solutions. Typically,
the two stabiliziny constituents are added in the acid
form or as the alkali metal or ammonium salts thereof.
A commercially available material suitable for use is
sold under the trade mark DEQUEST 2010 by Monsanto
Chemical Company and comprises l-hydroxy ethylidene-l,l
diphosphonate.
The diphosphonic acid or diphosphonate consti-
tuent can be present in the operating hath in an
amount of about 0.05 up to about 3 g/l with amount of
about 0.1 to about 0.5 g/l being preferred. The citric
acid or citrate constituent can be present in the ope-
rating bath from about 0.1 to about 10 g/l with amounts
of about 0.5 to about 1.5 g/l being preferred.
An optional but preferred constituent of the
~$
f- ~
~228130n
treating bath comprises a silicate compound present
in an amount effective to provide an improved corro-
sion protection and hardness to the passivate film
formed on the treated substrates. The silicates to
be used and the amounts in which they should be
used are discussed in more detail below in connection
with the sixth aspect of the present invention.
In addition, the bath further contains at
least one additional metal ion selected from the
group consisting of iron, cobalt, nickel, molybdenum,
manganese, aluminium, lanthanum, lanthanide mixtures
and cerium as well as mixtures thereof. The foregoing
metal ions or mixtures of metal ions are conveniently
introduced into the bath by way of bath soluble and
compatible metal salts including the sulphates,
nitrates, or halide salts, as discussed for the
second to fourth aspects and such materials as are
discussed above for those aspects can be and desir-
ably are used in this aspect of the invention.
The foregoing metal ions or combinations
thereof with the exception of cerium ions are em-
ployed for producing a clear to a light-blue
passivate film. When a light-yellow iridescent
passivate film is desired, cerium ions are employed,
preferably in combination with one or more of the
other metal ions to produce a passivate film simula-
ting in appearance the light yellow passivate films
heretofore obtained employing hexavalent chromium
passivating solutions which have been recognised
and embodied is ASTM specifications in view of their
characteristic colour and associated excellent corro-
sion resistance. The cerium ions can be introduced
.~
i22800()
31
in the manner discussed above in connection with the
first third and fourth aspects.
The concentration of the additional metal ions
other than cerium ions for appropriate activation of
the treating bath to produce a clear to blue-bright
appearance should be controlled in the manner
discussed in connection with the fourth aspect of
the invention.
When the operating bath is to contain an
organic carboxylic acid or salt thereof as discussed
in connection with the fourth aspect of the present
invention, the teaching there given should be
followed. However, the presence of a silicate com-
pound in the operating bath as discussed below in
connection with the sixth aspect of the present
invention has been found to also contribute to im-
proved clarity of the passivate film, and accordingly,
the use of the organic carboxylic acid addition agent
is usually unnecessary when a silicate compound is
employed in the bath.
The operating bath in accordance with this
fifth aspect of the invention can conveniently be
prepared by employing a concentrate containing the
active constituents with the exception of the
oxidizing agent and cerium ions, if used, which is
adapted to be diluted with water to form a bath con-
taining the constituents within the desired concentra-
tion range. Similarlyr replenishment of the bath on
a continuous or intermittent basis can be achieved
employing a concentrate of the active constituents
with the exception of the oxidizing agent and cerium
ions, if used, which is added separately to the
operating bath. Typically, a bath make-up concentrate
can contain from about 10 to about 80 g/l chromium
ions, from about 5 to about 50 g/l of at least one
'.~
~ 228~)00
32
additional metal, ion of the group consisting of iron,
cobalt, nickel, molybdenum, manganese, aluminium,
lanthanum, lanthanide mixture or mixtures thereof,
halide ions up to about 50 g/l, from about 5 to about
30 g/l of a silicate compound, if used, calculated as
SiO2; and a suitable surfactant in an amount up to
about 5 g/1 if employed. Such a make-up concentrate
is adapted to be diluted with about 98 volume percent
water to produce an operating bath containing the
active constituents within the ranges specified. The
oxidizing agent such as hydrogen peroxide, for
example, is separately introduced into the bath pre-
ferably in a form commercially available containing
from about 35 to 40 percent by volume hydrogen
peroxide. The cerium ions, when employed, are pre-
ferably introduced in the form of an aqueous acid
solution of cerous chloride or ceric sulphate having
cerium ion concentration of from about 200 to about
320 g/1 and about 60 to about 100 g/1, respectively.
Such cerium concentrates may be conveniently com-
prised of the commercially available materials
hereinbefore described available from Molycorp, Inc.
The foregoing trivalent chromium concentrate
containing the metal ions and acid components in
combination with an inorganic silicate compound has
a tendancy to form precipitates during prolonged
storage due to the high concentrations and acidic
conditions present. Accordingly, such foregoing
concentrates are normally diluted with water
shortly after preparation to provide an operating
bath containing the active constituents in the
desired concentrations. Concentrates of substan-
tially improved stability and prolonged shelf
.
- 122800~
33.
storage life can be provided by the use of organic
silicates as discussed below in connection with the
sixth aspect in combination with the trivalent chro-
mium ions, and optionally, halide ions and a wetting
agent. Such stable concentrations conventionally
contain from about 10 to about 80 g/l trivalent chromium
ions, about 5 up to about 50 g/l of an organic quater-
nary ammQnium silicate calculated as SiO2, halide
ions up to about 50 g/l and a surfactant in an amount
up to about 5 g/l. Such stable concentrate is adapted
to be used in conjunction with a second concentrate
containing the acid components, the additional metal
ions in an amount of about 5 to about 50 g/l, up to
80 g/l of the organic carboxylic acid and/or salt
additive agent if used. Such second concentrate can
also optionally contain a portion or all of the halides
and wetting agents if not employed in the first tri-
valent chromium concentrate.
In the preparation of such a trivalent chromium/
silicate concentrate, the organic silicate is first
diluted with water to the desired concentration range
whereafter the trivalent chromium constituent is added
along with the optional halide and wetting agent, if
employed. A particularly suitable commercially avai-
~ 25 lable organic silicate compound comprises QURAM 220
(trade mark) available from Emery Industries which
comprises a quaternary amine silicate.
The diphosphonic acid and citric acid and/or
diphosphonate and citrate stabilizing additive can be
incorporated in any of the foregoing concentrates
including the peroxide concentrate in an amount to
12Z800~
34
attain the desired concentration in the operating
bath. Alternatively, the stabilizing additive can be
prepared as a separate aqueous concentrate containing
from about 30 to about 170 g~l of the diphosphonic/
diphosphonate compound in admixture with about 160
to about 500 g/l of the citric acid/citrate compound
and added separately to the operating bath LO provide
the desired working concentration in accordance with
the limits hereinbefore specified, and typically,
4-5 g/l of the stabilizer concentrate. In accordance
with a preferred practice, the stabilizing additive
is incorporated directly in the chromium containing
concentrate, the cerium ion concentrate in the case
of a yellow passivate process, or in the second
concentrate employed in conjunction with the organic
silicate concentrate in amounts of about 3 to about
17 g~l diphosphonic acid/diphosphonate compound and
about 16 to about 50 g/l citric acid/citrate compound.
As discussed above for the first to fourth
aspects the treating bath can be applied to the sub-
strate in a variety of ways and the process conditions
described for these aspects can and desirably should
be used for this fifth aspect of the present
invention.
At the conclusion of the passivation treatment,
the substrate is extracted from the treating solution
and is dried such as by warm circulating air. Ordin-
arily, such passivated substrates, particularly work
pieces processed while supported on a work rack are
characterised as having a uniform passivate film over
the surfaces thereof requiring no further processing.
In the case of small work pieces which are treated
,~
122800~)
in bulk such as in a rotating processing barrel, some
damage such as scratches can occur in the passivate
film during treatment and it is desirable in such
instances to subject such work pieces to a post
silicate rinse treatment (as discussed below as the
seventh aspect of the present invention) to seal any
such surface imperfections thereby substantially
improving the corrosion protection of barrel-processed
parts.
when such an optional post passivation silicate
rinse treatment is employed, the substrate following
the passivation treatment is preferably subjected to
at least one or a plurality of water rinse steps
usually at room temperature to remove residual pas-
sivate solution from the surfaces thereof whereafter
the substrates are contacted with the post silicate
rinse solution in accordance with the teaching given
below in connection with the seventh aspect of the
present invention.
According to the sixth aspect of the present
invention there is provided a treating solution which
aims to reduce the severity of a problem of damage
to the passivate of passivated workpieces during sub-
sequent processing. Thus while improvements have been
made in trivalent chromium passivate compositions and
processes to produce commercially acceptable passivate
films, such films as initially formed have been found
in some instances to lack sufficient initial hardness
to enable handling of the substrate through further
work stages without encountering damage to the pas-
sivate film. Additionally, such trivalent chromium
passivate compositions and processes have also been
found in some instances to lack optimum corrosion
resistance, hardness and durability, and produce
0~
36
films which are somewhat cloudy and lack optimum
clarity from an appearance standpoint.
Thus this sixth aspect of the present invention
aims to provide a treating solution and process which
is effective to impart improved corrosion resistance
to zinc, zinc alloy, cadmium and cadmium alloy, as
well as aluminium and magnesium surfaces and to impart
a desirable surface finish which can range from a
clear bright to a light blue-bright to a yellow
iridescent appearance, which produces a passivate
film of improved corrosion resistance, hardness,
durability, clarity and initial hardness, which pro-
cess is simple to control and operate and which is
of efficient and economical operation.
lS The benefits and advantages of the sixth
aspect of the present invention are achieved in
accordance with the composition aspects thereof by
providing an aqueous acidic treating solution con-
taining as its essential constituents, chromium ions
substantially all of which are present in the tri-
valent state preferably at a concentration of from
about 0.05 grams per litre (g/l) up to saturation
(and which can be introduced as discussed for the
second to fifth aspects), hydrogen ions preferably
to provide a solution pH of about 1.2 to about 2.5
which can be conveniently introduced by mineral
acids such as sulphuric acid, nitric acid, or hydro-
chloric acid, an oxidizing agent of which hydrogen
peroxide itself is preferred, preferably present in
an amount of about 1 to about 20 g/l, a bath soluble
and compatible silicate compound present in an amount
effective to impart increased corrosion resistance
and hardness to the passivate film (preferably
present in an amount of about 0.01 to about S g/l
calculated as SiO2), and at least one additional
37
metal ion selected from the group consisting of iron,
cobalt, nickel, molybdenum, manganese, aluminium,
lanthanum, lanthanide mixtures and cerium, as well
as mixtures thereof present in an amount effective to
activate the bath and formation of a chromium pas-
sivate film of the desired appearance on the substrate
treated. As mentioned for the earlier aspects of the
invention, the solution may optionally contain halide
ions for imparting additional hardness to the coating,
and optionally a wetting agent. It may also incorpo-
rate a bath soluble compatible organic carboxylic
acid present in an amount effective to further impart
initial hardness and clarity to the passivate film.
In this sixth aspect of the invention whilst
it is applicable in the same way as the first aspeGt
in the case of decorative zinc electroplatings, a
further enhancement of th~ appearance of such sub-
strates in addition to the corrosion resistance
imparted is achieved by the passivate film which
ranges from a clear bright to a light blue bright
appearance simulating that of a chromium deposit or
alternatively, a clear light-yellow appearance
simulating that obtained by use of prior art hexa-
valent chromium solutions.
A further essential constituent of the treating
bath in accordance with the sixth aspect of the inven-
tion is the silicate compound present in an amount
effective to provide an improved corrosion protection
and hardness to the passivate film formed on the
treated substrate. The silicate compound may comprise
a bath soluble and compatible inorganic or organic
silicate compound as well as mixtures thereof which
are preferably present in an amount of about 0.01
up to about 5 g/i calculated as SiO2 with concentra-
.~
1~28~:10~
38
tions of about 0.1 to about 0.5 g/l being preferred.
When inorganic silicates are employed, concentrations
above about 2 g/l in the operating bath are undesir-
able because of the tendency of the silicate to form
fine flocculent precipitates with the metal ions
present in the bath under the acidic conditions
present which contributes towards bath instability.
Organic silicates, on the other hand, provide for
improved bath stability and are preferred for the
formation of make-up and replenishment concentrates
because of the improved stability and prolonged
shelf life.
Inorganic silicates suitable for use in the
practice of the present invention include alkali
metal and ammonium silicates of which sodium silicate
(Na2O.xSiO2(x=2-4) and potassium silicate (~2O.ySiO2
(y-3-5) are preferred for economical reasons. Organic
silicates which can also be satisfactorily employed
include quaternary ammonium silicates which include
tetramethyl-ammonium silicate, phenyltrimethylammon;um
silicate, disilicate and trisilicate, and benzyltri-
methylammon~um silicate and disilicate. Such silicates
meeting the purposes of this invention may be ex-
pressed by the following general formula:
RoR':xsio2 yH2o
Where R represents a quaternary ammonium radical
substituted with four organic groups selected from
the groups alkyl, alkylene, alkanol, aryl, alkylaryl
or mixtures thereof, R' represents either R or a
hydrogen atom,x equals 1 to 3 and y equals 0 to 15.
'q~.Z
l~Z1300~
39.
Such water soluble organic silicates including
their synthesis and characterization are more fully
described in the literature such as the article by
Merrill and Spencer, "Some Quaternary Ammonium Sili-
cates", published in the Journal of Physical and
Colloid Chemistry, 55, 187 (1951). Similar silicates
including typical syntheses thereof are also disclosed
in United states Patent No. 3,993,548.
In addition, the bath further contains at least
additional metal ion selected from the group
consisting or iron, cobalt, nickel, molybdenum,
manganese, aluminium, lanthanum, lanthanide mixtures
and cerium as well as mixtures thereof. The foregoing
metal ions or mixtures of metal ions are conveniently
introduced into the bath by way of bath soluble and
compatible metal salts including the sulphates,
nitrates, halide salts, as discussed for the second to
fifth aspects and such materials as are discussed above
for those aspects can be and desirably are used in
this aspect of the invention.
The foregoing metal ions or combinations thereof
with the exception of cerium ions are employed for
producing a clear to a light-blue passivate film. When
a light-yellow iridescent passivate film is desired,
cerium ions are employed, preferably in combination
with one or more of the other metal ions to produce a
passivate film simulating in appearance the light-
yellow passivate films heretofore obtained employing
hexavalent chromium passivating solutions which have
~2~
been recognized and embodied in ASTM specifications
in view of their characteristic colour and associated
excellent corrosion resistance. The cerium ions can
be introduced in the manner described above in
connection with the first, third, fourth and fifth
aspects.
The concentration of the additional metal ions
other than cerium ions for appropriate activation of
the treating bath to produce a clear to blue-bright
appearance should be controlled in the manner dis-
cussed in connection with the fourth and fifth
aspects of the present invention.
When the operating bath is to contain an
organic carboxylic acid or salt thereof as discussed
in the fourth and fifth aspects of the present
invention the teaching there given should be
followed.
The presence of the silicate compound in the
operating bath in accordance with this sixth aspect
of the invention has unexpectedly been found to also
contribute to improved clarity of the passivate
film, and accordingly, the use of the organic carbo-
xylic acid addition agent is not essential when a
silicate i5 present in the bath in accordance with
this aspect of the invention though it may be
desirable.
The operating bath in accordance with this
sixth aspect of the invention can conveniently be
prepared by empioying a concentrate containing the
active constituents with the exception of the
oxidizing agent and cerium ions, if used, which is
adapted to be diluted with water to form a bath
containing the constituents within the desired
concentration range. Similarly, replenishment of
'i"-
~LZ281)0~)
41
the bath on a continuous or intermittent basis can
be achieved employing a concentrate of the active
constituents with the exception of the oxidizing
agent and cerium ions, if used, which is added sepa-
rately to the operating bath. Typically, a bath make-
up concentrate can contain from about 10 to about
80 g/l chromium ions, from about 5 to about 30 g/l
of the silicate compound calculated as SiO2, from
about 5 to about 50 g/l of at least one additional
metal ion of the group consisting of iron, cobalt,
nickel, molybdenum, manganese, aluminium, lanthanum,
lanthanide mixture or mixtures thereof, halide ions
up to about 50 g/l and a suitable surfactant in an
amount up to about 5 g/l if employed. Such a make-up
concentrate is adapted to be diluted with about
98 volume percent water to produce an operating bath
containing the active constituents within the ranges
specified. The oxidizing agent such as hydrogen
peroxide, for example, is separately introduced into
the bath preferably in a form commercially available
containing from about 35 to 40 percent by volume
hydrogen peroxide.
The cerium ions, when employed, are preferably
introduced in the form of an aqueous acid solution of
cerous chloride or ceric sulphate having cerium ion
concentration of from about 200 to about 320 g/l and
about 60 to about 100 g/l, respectively. Such cerium
concentrates may be conveniently comprised of the
commercially available materials hereinbefore
described available from Molycorp, Inc.
42 12Z8~10~)
The foregoing trivalent chromium concentrate
containing the silicate compound, metal ions and
acid components has a tendency to form precipitates
during prolonged storage due to the high concentra-
tions and acid conditions present. Accordingly, such
foregoing concentrates are normally diluted with
water shortly after preparation to provide an operat-
ing bath containing the active constituents in the
desired concentrations. It has been further discovered
in accordance with this sixth aspect of the present
invention that concentrates of substantially improved
stability and prolonged shelf storage life can be
provided by the use of organic silicates of the types
heretofore set forth in combination with the trivalent
chromium ions and, optionally, halide ions and a
wetting agent. Such stable concentrates conveniently
contain from about 10 to about 80 g/l trivalent
chromium ions, about 5 up to about 50 g/l of an
organic quaternary ammonium silicate calculated as
SiO2, halide ions up to about 50 g/l and a surfactant
in an amount up to about 5 g/l. Such stable concen-
trate is adapted to be used in conjunction with a
second concentra~e containing the acid components,
the additional metal ions in an amount of about 5 to
about 100 g/l, up to 80 g/l of the organic carboxylic
acid and/or salt additive agent if used. Such second
concentrate can also optionally contain a portion or
all of the halides and wetting agents if not employed
in the first trivalent chromium concentrate.
In the preparation of such a trivalent chromium/
~r
43 12 2 8 00 ~
silicate concentrate, the organic silicate is first
diluted with water to the desired concentration range
whereafter the trivalent chromium constituent is
added along with the optional halide and wetting
agent, if employed. A particularly suitable commer-
cially available organic silicate compound comprises
Quram 220 available from Emery Industries which
comprises a quaternary amine silicate.
This sixth aspect of the present invention
further encompasses a novel concentrate composition
suitable for make-up of the operating bath by dilu-
tion with water containing as its essential consti-
tuents trivalent chromium ions and an organic
quaternary ammonium silicate which provides compati-
bility and storage stability over prolonged timeperiods.
As discussed above for the first to fifth
aspects the treating bath can be applied to the
substrate in a variety of ways and the process
conditions described for these aspects can and
desirably should be used for this sixth aspect of
the present invention.
At the conclusion of the passivation treatment,
the substrate is extracted from the treating solu-
tion and is dried such as by warm-circulating air.
Ordinarily, such passivated substrates, particularly
work pieces processed while supported on a work rack
are characterized as having a uniform passivate film
over the surfaces thereof requiring no further
processing. In the case of small work pieces which
_.~ r
..: ..
1~2800~
44
are treated in bulk such as in a rotating processing
barrel, some damage such as scratches can occur in
the passivate film during treatment and is desirable
in such instances to subject such work pieces to
post silicate rinse treatment (as discussed below
as the seventh aspect of the present invention) to
seal any such surface imperfections thereby substanti-
ally improving the corrosion protection of barrel-
processed parts.
When such an optional post passivation silicate
rinse treatment is employed, the substrate following
the passivation treatment is preferably subjected to
at least one or a plurality of water rinse steps
usually at room temperature to remove residual
passivate solution from the surfaces thereof where-
after the substrates are contacted with the post
silicate rinse solution in accordance with the
teaching given below in connection with the seventh
aspect of the present invention.
According to the seventh aspect of the present
invention there is proved a treating process which
addresses the same problem as the sixth aspect of the
present invention namely that of damage to the passi-
vate of the passivated work pieces during subsequent
processing. Thus while improvements have been made in
trivalent chromium passivate compositions and
processes to produce commercially acceptable
passivate films, such films as initially formed
have been found in some instances to lack
sufficient initial hardness to enable handling
of the substrate through further work stages
lZ;~300{~
without encountering damage to the passivate film.
Additionally, such trivalent chromium passivate compo-
sitions and processes have also been found in some
instances to lack optimum corrosion resistance,
hardness and durability, and produce films which are
somewhat cloudy and lack optimum clarity from an
appearance standpoint.
Thus, this seventh aspect of the present
invention aims to provide a process which is effective
to impart improved corrosion resistance to zinc, zinc
alloy, cadmium and cadmium alloy, as well as aluminium
and magnesium surfaces and to impart a desirable
surface finish which can range from a clear bright to
a light blue-bright to a yellow iridescent appearance,
which produces a passivate film of improved corrosion
resistance, hardness, durability, clarity and initial
hardness, which process is simple to control and operate
and which is of efficient and economical operation.
The benefits and advantages of the seventh aspect
of the present invention are achieved by a process which
provides an aqueous acidic treating solution containing
as its essential constituents, chromium ions substan-
tially all of which are present in the trivalent state
preferably at a concentration of from about 0.05 grams
per litre (g/l) up to saturation, (and which can be
introduced as discussed for the second to sixth aspects)
hydrogen ions preferably to provide a solution pH of
about 1.2 to about 2.5 which can be conveniently
introduced by mineral acids such as sulphuric acid,
nitric acid, or hydrochloric acid, an oxidizing agent
1228()0~)
46.
of which hydrogen peroxide itself is preferred,
preferably present in an amount of about 1 to about
20 g/1, at least one additional metal ion selected from
the group consisting of iron, cobalt, nickel, molybdenum,
manganese, aluminium, lanthanum, lanthanide mixtures
and cerium as well as mixtures thereof, contacting the
substrate with the said aqueous acidic solution for
a period of time sufficient to form a passivate film
thereon, and contacting for a period of at least about
one second the passivated substrate with a dilute
aqueous rinse solution containing a bath soluble and
compatible silicate compound present in an amount
effective to impart improved corrosion resistance and
hardness to the passivate rilm, and thereafter drying
the passivated silicate rinsed substrate.
The aqueous acidic solution may be as described
in connection with any of the first to sixth foregoing
aspects, and it may be used in the same way.
Following the passivation treatment, the subs-
trate is preferably subjected to one or a pluralityof water rinse steps which may be at room temperature
or at elevated temperatures whereafter the passivated
substrate is contacted with a dilute aqueous silicate
solution in the form of a final rinse step. The con-
tact time of the passivated substrate with the silicatesolution may range for a period of at least about on~
second up to about one minute or longer and the silicate
solution may range in temperature from about 50 up to
about 150F (10 to 66C). Following the silicate
rinse step, the substrate is dried such as by circulatin~
hot air, for example.
12X~o~
47.
The aqueous silicate rinse solution preferably
contains as its essential constituent, a bath soluble
and compatible inorganic or organic silicate compound
as well as mixtures thereof present in an amount of
about 1 to about 40 g/l, and preferably from about 5
to abou~ 15 g/l (calculated as SiO2). Inorganic
silicates suitable for use in the practice of the
present process include alkali metal and ammonillm
silicates of which sodium silicate (~a20 xSiO2 (where
x equals 2 to 4)) and potassium silicate (K20 ySiO2
(where y equals 3 to 5)) are preferred for economic
reasons. Organic silicates which can also be satis-
factorily employed include quaternary ammonium silicates
which include tetramethylammonium silicate, phenyltri-
methylammonium silicate, disilicate and trisilicate,
and benzyltrimethylammonium silicate and disilicate.
Such silicates suitable for use in the present inven-
tion have the following general formula:
RoR~:xsio2:y~2o
where R represents a quaternary ammonium radical
substituted with four organic groups selected from the
groups alkyl, alkylene, alkanol, aryl, alkylaryl ox
mixtures thereof, and ~' represents either R or a
hydrogen atom, and x equals 1 to 3 and y equals O to 15.
Such water soluble organic silicates and their
synthesis and characterization are more fully described
in the literature such as the article by Merrill and
Spencer, "Some Quaternary Ammonium Silicates", published
in the Journal of Physical and Colloid Chemistry, 55,
187 (1951). Similar silicates and a typical synthesis
- 122800~)
4~.
thereof are also disclosed in United States Patent No.
3,993,548.
Bec~use of the relatively higher cost of such
organic silicates, the silicate rinse solution prefe-
rably comprises inorganic silicates of which thepotassium and sodium silicates as hereinabove des-
cribed are particularly preferred.
In addition to the silicate compound, the
silicate rinse solution can optionally contain a bath
soluble and compatible wetting agent for enhancing con-
tact with the passivated surface present in conventional
amount of about 0.05 up to about 5.0 g/l. The silicate
rinse may also optionally include an emulsifiable
organic substance such as an emulsifiable oil e.g.
present in an amount of from about 1 up to about 50
g/l to provide an oily film on the non-electroplated
interior surfaces of ferrous substrates to provide
temporary protection against rusting during further
processing steps of the parts. When such parts have
surfaces which are completely passivated such as,
for example, zinc die castings, the use of the optional
emulsifiable oil is not necessary.
Similarly, there are applications where an oil
is not desired but temporary rust protection of
interior unplated surfaces is still required. In
these cases, a final rinse containing an alkali metal
or ammonium nitrite such as sodium nitrite e.g. in an
amount of about 0.1 to about 1.0 g/l may be used.
In addition a wetting agent or combination of wetting
agents is preferably used in conjunction with the
sodium nitrite e.g. in the amount of about 0.05 to
about 5.0 g/l. The presence of silicates in the final
rinse is also compatible with this treatment.
49~ 80 0 ~
The invention may be put into practice in various
wavs and a number of specific embodiments will be described
to illustrate the invention with reference to the accom-
panyins examples.
5. Examples 1.1 and 1.2 relate to the first aspect
of the invention which provides a chromium-like passivate
through using a bath free of chromium ions.
Exam~les 2.1 to 2.8 relate to the second aspect
of the invention which utilizes iron and cobalt as the
lO.metallic activator and also incorporates trivalent
chromium to produce bright bluish passivates.
Exam~les 3.1 to 3.5 relate to the third aspect
of the invention which utilizes cerium as the metallic
activator and again incorporates trivalent chromium
15.but this time gives a yellow passivate similar to hexa-
valent chromium passivates.
Examples 4.1 to 4.3 relate to the four~l aspect
of the invention which utilizes a carboxylic acid in
baths of the same general types as s~own in the Examoles
20.of the second and third aspects. The carboxylic acid
enhances the initial hardenino of the passivate.
Examples 5.1 to 5.8 relate to the fifth aspect of
the invention which utilizes a bath soluble silicate in
the passivate bath as well as trivalent chromium in
25.baths of the same general types as shown in the examples
of the second and fourth asoects. The silicate enhances
initial hardening of the passivate and corrosion resistance~
Examnles 6.1 to 6.5 relate to the sixth asPect
of the invention which utilizes a mixture of citric acid
30.and a particular phosphonic acid to inhibit loss of
oxidizing agent and increase of pH during use of the baths
- ~ lZ28~0~
of the tvpes described in the second and fifth aspects.
Examples 7.1 to 7.3 relate to the seventh
aspect of the invention which is a post passivation
silicate rinse Process which produces hardenina of
the passivate.
51. 122800~)
' EXAMPLE 1 1
A chromium-free passivating concentrate was
prepared containing 12 g/l ammonium bifluoride, 12 g/l
ferrous ammonium sulphate, 80 g~l cobalt sulphate, and
S. 4.5~ by volume of concentrated sulphuric acid. An
operatins bath was prepared comprising water to which 2%
by volume of the forego,ing passivating concentrate was
added in addition to l.S volume percent hydrogen peroxide
(38% concentration). The operating bath had a nominal
10. pH of about l.S to about 2Ø
Test panels carrying a bright electroplated zinc
deposit which had been water rinsed after the electro-
plating step and which were rinsed in a 5% by volume
dilute nitric acid solution were immersed in the ~perating
lS. passivating bath for a period of 20 seconds in the
presence of mild agitation. Thereafter the test ~anels
- were water rinsed and air dried. The ~es~ panels after
drying were visually inspected and ~ere characterized as
having a uniform clear bluish passi'vating film on the
20. surface the-reof. The operating bath had a nominal pH
of about l.S to about 2Ø
EXAMPLE 1.2
. .
In order to produce a li.ght yellow iridescent
25~ passivate film on z1nc electroplated test panels, cerium
ions were introduced in a test operating bath containing
2% by vo~ume of the chromium-free passivatinq concentrate
described in Example 1.1. 2~ by volume of a cerium
sulphate concentrate comprising a 6% cerium sulphate (Ce
30] (S04)2) solution $n a dilute sulphuric acid solution and
1~5~ by volume of a hydrogen peroxide concentrate (3~%).
The normal pH of thecperating bath was about 1.~ ~o
about 2Ø
., .
.~,
52 12~8~
The zinc test panels after plating, water
rinsing and a nitric acid dip were immersed in the
test solution in the presence of mild agitation for
a period of 45 seconds. The treated test panels were
water rinsed and air dried. A visual inspection of
the surface of the test panel revealed a substantially
uniform light-yellow iridescent passivate film.
EXAMPLE 2.1
An operating bath was prepared containing:
Ingredient Concentration, g/l
-
Cr2(So4)3 2.2
N~4HF2 .18
H2SO4 1.2
22 5.3
4S 4 0.25
SO4 .7H2O 1.6
* Ferrous Ammonium Sulphate = Fe(SO4) (NH4)2SO4 6H2O
Steel test panels were subjected to an
alkaline, non-cyanide electroplating step to deposit
a zinc plating thereon after which they were thor-
oughly water rinsed and immersed with agitation in
the above operating bath for a period of 20 seconds.
At the conclusion of the treatment, the passivated
panels were warm water rinsed, and air dried. An
inspection of the coating on the panels after
drying revealed an exceptionally bright clear-bluish
3~ colouration with no haziness. Additionally, the
coating exhibited the appearance of a bright nickel
,,~
~.
53 ~22800~
chromium electroplating and also exhibited excellent
smear resistance on light finger-rubbing.
EXAMPLE 2.2
An operating bath was prepared containing:
Ingredient Concentration, g/l
Cr2(SO4)3 5.6
NH~HF2 0.4
H2SO4 2.7
22 5-3
NH4S04 0.58
CoSO4 . 7H20 3.75
The operating bath of Example 2.2 is similar
to that of Example 2.1 with the exception that the
trivalent chromium, ammonium bifluoride, sulphuric
acid, iron and cobalt constituents are all at higher
concentrations. Zinc plated test panels treated with
the bath of Example 2.2 produced results substantially
equivalent to those obtained with the operating bath
of Example 2.1
EXAMPLE 2.3
An operating bath was prepared containing:
Ingredient Concentration, g/l
Cr2~SO4)3 3.0
4 2 0.24
2S4 1.54
2 2 5 3
4 4 0.25
4SO4 2.1
54 ~ ~ 2 ~o ~
*Nickel Ammonium Sulphate - NiSO4 (NH4)2SO4 6H2O
Zinc plated test panel treated with this
operating bath under the same conditions as described
in Example 2.1 were observed, after drying, to have
a coating which was very bright with a clear bluish
colouration and no haziness. The coating also ex-
hibited good smear resistance on light finger
rubbing.
1 EXAMPLE 2.4
An operating bath was prepared identical to
that as set forth in Example 2.3 with the exception
that 1.6 g/l of nickel sulphate was employed in
place of 2.1 g/l of nickel ammonium sulphate. The
zinc plated test panels treated in the manner as
previously described in Example 2.1 employing the
treating solution of Example 2.4 produced results
substantially comparable to those obtained with the
treating bath of Example 2.3 except that the coating
had a slightly less bluish colouration.
EXAMP~ES 2.SA to 2.5E
. _
A series of passivating solutions were pre-
pared for treating zinc plated steel test panels to
evaluate their relative corrosion resistance to a
5 percent neutral salt spray after passivation. The
composition of the solutions 5A, 5B, 5C and 5D are
given in Table 1 below:
~28~)00
Table 1
Concentration, g/1
Ingredient 2.SA 2.5B 2.5C 2.5D
Cr2(SO4)3 3.0 3 0 3 0 3 0
4 2 0.24 0.24 0.24 0.24
H2SO4 1.54 1.54 1~54 1.54
H2O2 5.3 5.3 5.3 5.3
FeNH4S4 ~ 0.25 0.25 0.25
CoSO3 - - 1.6
NiNH4So4 - - - 2.1
Solution 2.5A contains only trivalent chromium
ions; solution 2.5B additionally contains ferrous
ions; solution 2.5C contains a combination of iron
and cobalt ions while solution 2.5D contains a
combination of iron and nickel ions.
In addition to the foregoing operating solu-
tions, a traditional hexa~alent chromium passivating
solution ~E~ample 2.SE) was prepared to serve as a
control containing 0.63 g~1 sodium dichromate,
0.63 g/l a~nonium bifluoride, 0.01 g/l sulphuric
acid, 0.65 g/l nitric acid. This solution is
designated as solution 2.5E.
Duplicate sets of 3 inch by 4 inch (7.6 cms by
10.2 cms) steel panels were cleaned and zinc plated
using a non-cyanide zinc plating electrolyte for fif-
teen minutes at a plating current density of 20 amperes
per square foot (ASF) (2.2 Amperes per Square decimi-
ter (ASD))whereafter they were thoroughly rinsed. Each set
of zinc plated test panels was then immersed in the
'~
,....
56. 1228~0~
respective treating solution for a ~eriod of twenty
seconds whereafter they were warm water rinsed, air-dried
and thereafter allowed to age twenty-four hours prior to
salt spray testing in accordance with ASTM standards.
5. The test panels were subjected to the five percent
neu~ral salt spray for a total of forty-three hours.
For further comparati~e purposes, a duplicate set of zinc
test panels without any passivation treatment was also
subjected to the neutral salt spray test. The results
lOo are set forth in Table 1.
TABLE 1
NEUTRAL SALT SPRAY TEST RESULTS
. _ _
EX~MPLE TEST PE~CE~T WHITE PERCENT
PANEL CORRQSION, ~ RED RUST, Q
15.
-20SE Untleate~ 50 ~0
2~5A 5A - 4$ - 55
2.5B 5B ^ 10 - 15 0
20 2.5C 5C less than 2 o
2.5D 5D less than 10 0
2D5E SE ~5 ~ S5 0
~ase~ on the foregoing test results it is apparent
25. ~ha~ the untreated ~inc ~lated test panel is a gross
failure, the test panel treated with solution 2.5A is
a failure; the test panels treated with solution 2.5B
are a marginal pass; the test panels treated with
solutions 2.5C and 2.5D pass the test; and the test ~anel
30. ~reated with soluti~n 2.5E is a failure.
57
EXAMPLE 2.6
An operating bath was prepared containing:
Ingredient Concentration, g/l
Cr2(SO4)3 3 0
4 2 0.24
H2SO4 1.54
N 4SO4 0.24
22 5 3
04 . H20 1. 0
Electroplated zinc test panels prepared in
accordance with the procedure as set forth in
Example 2.5 were immersed in the bath of Example 2.6
for a period of 30 seconds, warm water rinsed, air
dried and allowed to age 24 hours prior to 5 percent
neutral salt spray testing. For comparative purposes,
zinc test panels were treated with the solutions 2.5A
and 2.5E of Example 2.5 and subjected to the same
salt spray evaluation.
After 48 hours salt spray, an inspection of
the several test panels revealed that the panels
treated with the solution of Example 2.6 had superior
corrosion resistance to that of the panels treated
with solutions SA and 5E.
EXAMPLE 2.7
An operating bath was prepared containing:
:;
1~2~300~
58
Ingredient Concentration g/1
Cr2(SO4)3 3.0
4 2 0.24
H2S4 1.54
4 4 0.24
22 5-3
2 4 2 1.0
Electroplated zinc test panels prepared in
accordance with Example 2.5 were immersed in the bath
of Example 2.7 for a period of 30 seconds, warm water
rinsed, air dried and allowed to age for 24 hours
prior to 5 percent neutral salt spray testing. For
lS comparative purposes, zinc test panels were treated
with the solutions 2.5A and 2.SE of Example 2.5 and
subjected to the same salt spray evaluation.
After 48 hours of salt spray test, an inspec-
tion of the panels revealed that the panels treated
with the solution of Example 2.7 had superior
corrosion resistance to that of the test panels
treated with solutions 2.5A and 2.5E.
EXAMPLE 2.8
An operating bath was prepared containing:
~22BO~)~
59
Ingredient Concentration, g/l
Cr2(SO4)3 3.0
4 2 0.24
5 H2SO4 1.54
4 4 0.24
22 5.3
(NH4)4(NiMoo24H6)4 4H2 1.0
Electroplated zinc test panels prepared in
accordance with the procedure described in Example
2.5 were immersed in the bath of Example 2.8 for a
period of 30 seconds, warm water rinsed, air dried
and allowed to age for 24 hours prior to a 5 percent
neutral salt spray test. For comparative purposes,
zinc test panels were treated with the solutions
2.5A and 2.5E of Example 2.5 and subjected to the
same salt spray evaluation.
After 48 hours salt spray, an inspection of
the panels revealed that the panels treated with the
solution of Example 2.8 had superior corrosion
resistance in comparison to the panels treated with
solutions 2.5A and 2.5E.
A relative comparison of the test panels pre-
pared in accordance with Examples 2.6, 2.7 and 2.8
revealed that the solution of Example 2.6 containing
iron ions and Molybdic acid and the solution of
Example 2.8 containing iron ions in combination with
ammonium 6-molybdonickelate possessed superior
corrosion resistance to the test panels treated
with the operating solution of Example 2.6 cont-
aining iron ions in combination with manganese ions.
- i228000
60.
The test panels treated in accordance with Examples 2.7
and 2.8 also possessed superior corrosion resistance to
test panels treated with the test solution 2.5B of
Example 2.5 containing only iron ions whereas the test
panels treated with the solution of Example 2.6 con-
taining both iron and manganese ions possessed corrosion
resistance somewhat comparable to that of panels
treated with solution 2.5B.
EXAMPLE 3.1
A concentrate 3.lA was prepared comprising an
aqueous acidic solution containing 25 g/1 trivalent
chromium ions introduced as chromium sulphate (KOREON
MF (trade mark) fro~ Allied Chemical Company), 12 g/l
15 ammonium chloride, 12 g/l ferrous ammonium sulphate
and 4% by volume of concentrated sulphuric acid.
A second aqueous acidic concentrate 3.lB was
prepared containing 60 g/1 tetravalent cerium ions
introduced as Ce(SO4)2 4H2O and 5% by volume concen-
20 trated sulphuric acid.
An operating bath was prepared comprising water
containing 2% by volume concentrate 3.1A, 2% by volume
concentrate 3.lB and 1.5% by volume of a 38Yo solution
of hydrogen peroxide. Electroplated zinc test panels
25 immersed in this operating bath for 40 to 60 seconds
had light-yellow iridescent passivate films on the
surfaces thereof.
EXAMPLE 3.2
A concentrate 3.2A was prepared similar to con-
~.
61 ~22~3~30~
centrate lA of Example 1 containing 25 g/l trivalent
chromium ions, 20 g/l sodium chloride, 40 g/l ferric
sulphate and 4% by volume concentrated sulphuric
acid.
An operating bath was prepared comprising water
containing 2% by volume concentrate 3.2A, 2% by volume
Concentrate 3.1B of Example 3.1 and from 1.5-3~ by
volume of a 38% solution of hydrogen peroxide. ~lectro-
plated zinc test panels immersed in the operating bath
produced results similar to Example 3.1.
EXA~PLE 3.3
A concentrate 3.3A was prepared similar to
concentrate 3.lA of Example 3.1 except that 6~ by
volume nitric acid was employed in place of 4
sulphuric acid.
An operating bath was prepared comprising water
containing 2% by volume concentrate 3.3A, 2% by volume
concentrate 3.lB of Example 3.1 and 1.5 - 3% by volume
of a 38% solution of hydrogen peroxide. Electroplated
zinc test panels immersed in the operating bath
produced results similar to Example 3.1.
EXAMPLE 3.4
A concentrate 3.4A was prepared similar .o
concentrate 3.2A of Example 3.2 except that 6~ by
volume nitric acid was employed in place of 4~ by
volume sulphuric acid.
An operating bath was prepared comprising water
containing 2% by volume concentrate 3.4A, 2% by volume
concentrate 3.lB of Example 3.1 and 1.5 - 3% by volume
of a 38% solution of hydrogen peroxide. Electropiated
zinc test panels immersed in the operating bath
62 1228t:)0~
produced results similar to Example 3.1.
EXAMPLES 3.5A to 3.5G
A series of seven aqueous test solutions were
prepared each containing 1 g/l trivalent chromium
ions, 1 g/l nitric acid, 1 g/l sulphuric acid, 7 g/l
hydrogen peroxide and having a nominal pH of about 1.5.
To each test solution controlled additions of metal
ions were made to evaluate the effect of such addi-
tions on the colour, hardness and salt spray resis-
tance of the passivate films produced on electro-
plated zinc test panels immersed in each test opera-
ting bath in the presence of mild agitation for a
period of about 30 seconds and at a temperature of
about 70F (21C).
The cerium ions were introduced as a CeC13
solution containing about 300 g/l cerium ions; the
manganese ions were introduced as MnSO4 H2O; the
ferric ions were introduced as Fe2(SO4)3 dissolved in
a dilute sulphuric acid solution; the molybdenum ions
were introduced as sodium molybdate dry salt; the
lanthanum ions were introduced as an LaC13 solution
containing about 85 ~/1 lanthanum ions; and the
cobalt ions were introduced as cobalt sulphate. The
test solutions are designated as Examples 3.5A to
3.5G and the concentration of metal ion additions
are summarised in Table 2.
63 ~228000
TABLE 2
METAL ION CONCENTRATION g/l
Example 3.5A 3.5B 3.5C 3.5D 3.5E 3.5F 3.5G
Metal Ion
CR+3
Ce+3 2 2 2 2 2 2 2
- O ~ 9
10 Fe+3 0.22 - - 0.08 0.08
Mo+6 _ - - 1.0
La+3 _ _ _ - 1.0
Co+2 _ _ _ - - - 0.13
15 Each test panel after immersion in the test
operating bath was water rinsed and air dried and was
visually inspected for colour and clarity. All of the
test panels treated in solutions 3.5A to 3.5G were of
substantially uniform light-yellow colour varying in
clarity from a clear yellow film to films which were
slightly hazy or hazy as set forth in Table 3. Each
test panel after air drying was immediately tested
for hardness of the passivate film by a light finger
rubbing. The comparative hardness test results of the
passivate film on the test panels treated in test
solutions 3.5A to 3.5G is set forth in Table 3. It
will be noted, that after a 24 hour aging of the test
panels, the passivate film thereon became hard and
rub resistant. The advantage of a passivate film which
is hard immediately after air drying is that it can
be handled for further processing without undergolng
damage to the deposited film. Each test panel treated
with test operating solutions 3.5A to 3.5G was also
.~
64 1 % 2 800 O
subjected to a neutral salt spray for a period of
72 hours and the surface area, expressed in terms of
a percentage, in which a white corrosion deposit was
formed is also tabulated in Table 3.
TABLE 3
TEST RESULTS
NEUTRAL SALT SPRAY
72 Hrs. - % White
EXAMPLE CLARITY HARDNESS Corrosion
_ .
3.5A Sl. haze Soft50
3.5B Sl. haze Soft100
3.5C Sl. haze Hard10
3.5D Haze Hard O
3.5E Sl. Haze Soft100
3.SF Clear Soft 2
3.5G Clear Hard 0
Based on the data as set forth in Table 2, from
a clarity and hardness evaluation, Example 3.5G is a
definite pass, Examples 3.5C and 3.5F are acceptable,
which Examples 3.5A, 3.5B and 3.5E are less acceptable
based on general appearance. From the standpoint of
corrosion resistance, Examples 3.5D, 3.5F and 3.5G are
definite passes, 3.5C a marginal pass, while Examples
3.5A, 3.5B and 3.SE are considered not acceptable
based on ASTM corrosion standard specifications for
a 72 hour neutral salt spray evaluation. It should be
pointed out, however, that each of the test samples
possess improved corrosion resistance in comparison
65 1 2~ ~ ~o ~
to an untreated electroplated zinc test panel and the
passivate films which failed the 72 hour neutral salt
spray test are nevertheless acceptable for less
rigorous service exposures. The corrosion resistance
provided by the Example 3.5G is substantially compara-
ble to that attainable with conventional prior art
hexavalent chromium passivate solutions of the types
heretofore known. It will also be appreciated that
variations in the types, combinations and concentra-
tions of the metal ions contained in the test solu-
tions can be made to optimize and improve the clarity,
hardness and corrosion resistance of the test panels
over the results as set forth in Table 3. The selec-
tion of a 72 hour neutral salt spray condition is
relatively severe and is generally employed for parts
subjected to exterior exposure such as in automotive
components. The 72 hour neutral salt spray test is
normally applied to yellow hexavalent chromium pas-
sivates although some specifications require only
48 hours while others require a 96 hour exposure~ The
72 hour test period was, accordingly, selected as
being of average severity.
EXAMPLES 4.lA to 4.lG
A series of trivalent chromium containing con-
centrates were prepared suitable for dilution with
water to make up an operating bath in further combina-
tion with an oxidizing agent and cerium or lanthanum
ions as follows:
12Z~3~0~
66
CONCENTRATE 4.lA
INGREDIEN_ CONCENTRATION, g/l
Cr+3 24
4 . H2O 25
Ferrous ammonium sulphate 12
Sodium fluoroborate 15
Succinic acld 25
Nitric acid (100~) 60
CONCENTRATE 4.lB
INGREDIENT CONCENTRATION, g/l
Cr+3 24
NaCl 20
Ferrous ammonium sulpha~e 25
Sodium succinate 55
Nitric acid (100%) 60
CONCENTRATE 4.1C
INGREDIENT CONCENTRATION, 9/1
Cr+3 24
Ferric ammonium sulphate 50
Sodium succinate 55
NaCl 20
Nitric Acid (100%) 60
....
67 12~8~)0~
CONCENTRATE 4.lD
INGREDIENT CONCENTRATION, g/l
Cr+3 24
Ferric ammonium sulphate 50
Succinic acid 25
NaCl 20
Nitric acid (100%) 60
CONCENTRATE 4.1E
INGREDIENT CONCENTRATION, g/l
Cr+3 24
Ferric ammonium sulphate 50
NaCl 20
Malonic acid 25
Nitric acid (100%) 60
CONCENTRATE 4.lF
NGREDIENT CONCENTRATION,g/l
Cr+3 24
Fe2(SO4)3 30
NaCl 20
Gluconic acid 20
Nitric acid (100%) 60
~800~
68
CONCENTRATE 4.1G
INGREDIENT CONCENTRATION, g/l
Cr+3 24
Ferric ammonium sulphate 50
NaCl 20
Maleic acid 25
Nitric acid (100%) 60
EXAMPLES 4.2A to 4.2G
A cerium ion concentrate was provided contain-
ing about 80 g/l ceric ions in the form of ceric
sulphate in a dilute sulphuric acid solution. An
oxidizing agent concentrate was also provided contain-
ing about 35% hydrogen peroxide. A series of operating
baths were prepared suitable for forming a yellow
passivate film on a substrate each containing 2% by
volume of the cerium ion concentrate, 2~ by volume of
the oxidizing agent concentrate, and 2% by volume of
one of the chromium concentrates 4.lA to 4.lG of
Examples 4.lA to 4.lG.
Steel test panels were subjected to an alkaline,
non-cyanide electroplating step to deposit a zinc
plating thereon after which they were thoroughly
water rinsed and immersed with agitation in each of
the test operating baths for a period of abo~t 30
seconds maintained at a temperature of about 70F
(21C) and having a pH ranging from about 1.5 to
about 2Ø At the conclusion of the passivation treat-
ment, the passivated panels were warm water rinsed
and air dried~ An inspection of the coating
69. 1 2 2 ~ 00 ~
on each of the test panels which had been immersed in
each of the operating test solutions revealed the form-
ation of a clear hard yellow passivate film.
5. EXAMPLES 4.3A to 4.3G
A lanthanum ion concentrate was provided contain-
ing about 60 g/l lanthanum ions in the form of a solution
of lanthanum chloride. An oxidizing agent concentrate
was also provided containing about 35% hydroqen peroxide.
10. A series of operating baths were prepared su.itable for
forming a blue-bright passivate film on a substrate
each containing 2% by volume of the lanthanum ion concen-
trate, 2% by volume of the oxidizi.ng agent concentrate,
and 2~ by volume of one of the chromium concentrates
15. 4.lA to 4.lG of Example 4.1.
-~inc plated test panels as described .i..n Examnle
....... 4.2.were lmmersed under.the conditions described i~l
Example 4.2.whereafter tl~ey-were warm water l~:insed ~ld
a~r drie*. An inspec~i.on of the coa~ing on each of the
20. test.panels after drving revealed an exceptionallv
. bright, clear, hard bluish coloured passivate film~
The yellow pass.ivated panels of Examples 4.2~,
: 4.2B and 4~2C produced using operating baths containing,
respectively,:concentrates 4.1A, 4.1B and 4~1C as herein-
. 250 above described wère aged for at least 24 hours and
subjected to neutral salt spray corrosion testing
according to ASTM procedure B-117. The followina Table 4
indicates the corrosion resis~ance .results t~lat were
obtained using these formulations:
30.
7~ -12 2 8 00 0
Table 4
Example Chromium Hours Neutral Salt S~rav
Concentrate 72 96
4.2A 4.lA Clear with Clear with
some dark some dark
spots. sPots.
5- 4.2B 4.lB Clear with Clear with
some dark some dark
spots. s~ots.
4.2C 4.lC Clear with Some dark
some dark snots - 1%
spots. white soots.
10 .
The above results show that panels treated with
operating baths containing concentrates A, B, and C
passed the 96 hour salt spray test. Similar results
were obtained with ~anels oroduced using the other
15. concentrates.
EX~MPLE 5.1
An ooerating bath suitable for de~ositing a yellow
passivate film on a receptive substrate was orovided by
20. forming a trivalent chromium containing concentrate
designated as "Concentrate 5.1A"having a comoosition as
follows:
CONCENTRATE 5.lA
Inqredient Concentration q/l
+3
25. Cr 50
Ferric ammonium sulohate 30
Sodium chloride 20
Nitric Acid (100%) 60
Succinic acid 20
30.
The trivalent chromium ions were introduced as
Cr2(S04)3.
7 ' ~22800~)
A cerium ion concentrate designated as "Concen-
trate 5.lB"~as provided containing about 80 g/l ceric
ions in the form of ceric sulphate in a dilute (about 5%)
sulphuric acid solution. An oxidizing aaent concentrate
5. was also provided containing about 35% hydro~en ~eroxide.
A sodium silicate concentrate was also provided contain-
ing 300 g/l sodium silicate calculated as SiO2.
A yellow passivate operating bath was prepared
comprising water containing 2% by volume of Concentrate
10. 5.1A, 2% by volume of the cerium ion Concentrate 5.1B,
2~ by volume of the oxid~ng agent concentrate and 0.4%
by volume of the sodium silicate concentrate.
Steel test panels were subjected to an alkaline,
non-cyanide electroplating step to deposit a 2inc plating
15. thereon after which they were thoroughly water rinsed
and immersed with agitation in the passivate operating
bath for a period of about 30 seconds at a temperature
of about 70F (21 C) and at a pH ranging from about 1.5
to about 2Ø The test panels were thereafter ex~racted
20. from the operating bath and were dried with recirculating
warm air.
The test panels after drving were visuallv inspected
and were observed to have a very hard clear yellow
passivate film. The test panels after aging for at least
25. 24 hours, were subject to a neutral salt spray corrosion
test according to AST~ Procedure B-117. The test panels
thus treated in accordance with the present process
exhibited excellent salt s~ray resistance after ex~osure
for a period of more than 96 hours.
30.
72. 1~8000
EXAMPLE 5.2
An operating bath suitable for depositing a vellow
passivate film on a receptive substrate was provided
by for~ing a trivalent chromium containing concentrate
5. designated as "Concentrate 5.2A" having a composition
as follows:
CONCENTRATE 5.2A
Ingredient Concentrati-on g/l
10. Cr+3 50
Ferric ammonium sulphate 40
Sodium chloride 20
Nitric Acid (100~) 60
Sodium silicate (calculated as SiO2) 10
15. A yellow passivate operating bath was prepared
comprising water containing 2~ by volume of Concentrate
5.2A, 2~ by volume of the cerium ion Concentrate-5.1B
of Example 5.1, and 2% by volume of the oxidizing aqent
concentrate of Example 5.1.
20. Test panels prepared in accordance with the pro-
cedure described in ExamPle 5.1 were immersed in the
operating bath for a eriod of about 30 seconds at a
temperature of about 70F (21C) and at a pH ranging from
about 1.5 to about 2Ø The treated test panels were
25. dried with recirculating warm air and the dried panels
were observed to have a very hard clear yellow passivate
film. The test panels after aginq were subjected to a
neutral salt spray corrosion test as aescribed in Example
5.1 and were observed to possess excellent salt spray
30. resistance after exposure for a period of more than 96
hours.
73. ~228~0~
EXAMPLE 5.3
An operatina bath suitable for depositing a
vellow passivate film on a receptive substrate was
provided by forming a trivalent chromium containinq
5. concentrate designated as "Concentrate 5.3A" having a
composition as follows:
CONCENTRATE 5.3A
In~redient Concentration g/l
10. Cr+3 5~
Ferric ammonium sulphate 40
Nitric acid (100%) 60
Sodium chloride 20
An operating bath was prepared comprislng water
15. containina.2% by volu~.e of Concentrate 5.3A, 2~ by
volume of the cerium ion containing Concentrate 5.lB
of Examnle 5.1, 2~ by volume of the oxidizing agent
concentrate of Example 5.1, and 0.5% by vol~ne of the
sodium silicate concentrate of Example 5.1.
20. Electroplated zinc test panels were treated in
the operating bath in accordance with the procedure as
described in Example 5.1 and after drying, were observed
to have a good clear yellow passivate film.
The test panels also possessed good salt sprav
25. resistance evidencing excellent corrosion protection.
EXAM~LE 5.4
An operating bath suitable for depositinq a yellow
passivate film on a receptive substrate was nrovided by
30. forming a trivalent chromium containing concentrate
74, 1~Z8~0~
incorporating a quaternarv amine silicate designated
as "Concentrate 5.4A" having a composition as follows:
` CONCENTRATE 5.4A
5. Ingredient Concentration g/l
C +3
Quaternary amine silicate* 15
Sodium chloride 15
* Quram 220, calculated as SiO2.
10. The trivalent chromium containing Concentrate
5.4A was subjected to prolonged storage and was observed
to possess excellent stability over prolon~ed storage
times.
In addition, a second concen~rate desianated as
15. "Concentrate 5.4R" was ~repared having a composition as
follows:
CONCENTRATE 5.4B
Ingredient Concentration g/l
20. Nitric Acid (100~) 60
Sulphuric acid (100%) 30
Ferric sulPhate 25
Ceriurn chloride 120
An operating bath was prepared comprising water
25. containing 2% by volume of Concentrate 5.4A, 2% by
volume of Concentrate 5.4B and 2% by volume of the
oxidizing agent concentrate as described in Example 5.1.
Zinc plating test panels were contacted with
the operating bath in accordance with the procedure
30. and under the conditions as described in Example 5.1
12i~8~0~
whereafter the test panels were dried with recircula-
ting warm air. The test panels were observed to have
an excellent hard and clear yellow passivate film and
possess excellent salt spray resistance showing zero
white corrosion formation after exposure to a neutral
salt spray test for a period of 96 hours.
EXAMPLE S.5
A second series of electroplated zinc test
panels were treated with the operating bath as pre-
viously described in Example 5.4 under the same
conditions whereafter the test panels were water
rinsed and thereafter post-rinsed for a period of
30 seconds in an aqueous solution at room temperature
containing 10 g/l sodium silicate calculated as SiO2.
The panels after the post rinse were extracted and
dried with warm air.
The test panels were inspected and observed
to possess a very hard clear yellow passivate film.
After aging, the test panels were subjected to a
neutral salt spray corrosion test and exhibited
excellent salt spray resistance after exposure of
96 to 140 hours. These tests also showed that when
a post silicate rinse treatment is employed, the
presence of some nitrate ions in the passivate
operating bath is desirable to avoid the formation
of some haze, in some instances, in the passivate
film as a result of the post dip operation.
EXAMPLE 5.6
An operating bath suitable for depositing a
blue-bright passivate film on a receptive substrate was
76. 12 2 8~0 0
provided by forming a concentrate designated as
"Concentrate 5.6A" having a composition as follows:
CONCENTRAT~ 5.6A
5. Ingredient Concentration g~l
Nitric acid (100%) 30
Sulphuric acid (100~) 20
Succinic acid 20
La~RE-C13 80
10. A passivate operating bath was prepared comDrising
water containing 3% by volume of Concentrate 5.4A of
Example 5.4, 3% by volume of Concentrate 5.6A and 3~
by volume of the oxidizing agent concentrate of Example
5.1.
15. Electroplated zinc test panels were treated with
the operating bath in accordance with the procedure as
pr~viously described in Example 5.1 and the test panels
after drying were observed to possess an excellent blue-
bright passivate film. The test panels also possessed
20. excellent corrosion resistance as shown by the ab-
sence of white corrosion after being subjected to a
neutral salt spray corrosion test for a period of from
48 up to 72 hours.
25. EXAMPLES 5.7.1 and 5.7.2
A trivalent chromium containing concentrate
was prepared desi~nated as "Concentrate 5.7A" havin~ a
composition as follows:
30.
77, 12 2 800
CONCENTRATE 5.7A
Inqredient C-oncentration -g/l
Cr 30
Sodium chloride 10
5. Sodium silicate (Calculated as SiO2) 10
An operating bath (Example 5.7.1) suitable for
depositing a yellow passivate film on a receptive
substrate was prepared by emploving 2% by volume of
Concentrate 5.7A, 2% by volume of Concentrate 5.4B of
10. Example 5.4 and 2% by volume of the oxidizing agent
concentrate of Example 5.1. On the other hand, an
operating bath (Examle 5.7.2) suitable for depositing
a blue-bright passivate film was achieved by employing
2% by volume of Concentrate 5.7A, 2~ by volume of
15. Concentrate 5.6A of Example 5.6 and 2% by volume of
the oxidizing agent concentrate of Example 5.1.
Test panels treated in accordance with the pro
cedure described in Example 5~1 evidenced excellent
passivate films and exhibited excellent corrosion pro-
20. tection.
EXAMPLE 5.8
An operating bath suitable for depositinq ablue-bright passivate film on a rece~tive substrate
25. was provided by forming a trivalent chromium containing
concentrate designated as "Concentrate 5.8A" havina a
composition as follows:
1228~)00
78.
CONCENTRATE 5.8~
Inqredient Concentration g/l
_
Cr 30
Sodium chloride 13
5. Sodium gluconate 10
Quaternarv amine silicate* 15
*Quram 220, calculated as SiO2
A second concentrate designated as "Concentrate
5.8B" was provided having a composition as follows:
10.
CONCENTRATE 5.8B
Ingredient Concentration g-/l
Nitric acid (100~) 60
Sulphuric acid (100%) 30
15- A12(S4)3 30
An operating bath was prepared comprising water
containing 3% by volume of Concentrate 5.8A, 3% by
volume of Concentrate 5.8B and 3% by volume of the oxid-
izing agent concentrate of Example 5.1.
20. Electroplated zinc test panels were treated in
accordance with the procedure described in Example 5.1
and after drying were observed to have a clear bright
passivate film. Testing of such panels in neutral salt
spray corrosion tests evidenced a corrosion resistance
25. of at least 12 up to 24 hours.
EXAMPLE 6.1
. .
An operating bath suitable for depositing a
yellow passivate film on a receptive substrate was
30. provided by forming a trivalent chromium concentrate
designated as "Concentrate 6.lA" havin~ a composition
as follows:
79- 12 ~ 8
CONCENTRATE 6.lA
Ingredient Concentration g/l
Cr 30
Quaternary Ammonium silicate 15
5. NaC1 15
The trivalent chromium ions were introduced as
Cr2(S04)3 while the silicate compound was introduced
as Quram 220 from Emery Industries.
A cerium ion concentrate designated as "Concen-
10. trate 6.1B" was provided having a composition as follows:
CONCENTRATE 6.lB
Ingredient Concentration q/l
.
HN03 (100~) 60
15. H2~04 (100~) 30
Fe23S04)3 25
Ce 120
The cerium ions were introduced by way of a
cerium chloride solution containing about 300 g/l Ce 3
20. ions.
In addition, an oxidizing agent concentrate was
provided containing about 35% hydrogen peroxide.
A series of one litre operatina baths were ~repared
comprising 3% by volume Concentrate 6. lA, 3~ bv volume
25. Concentrate 6.lB and 3% by volume of the oxidizina agent
concentrate. In order to simulate an aqed ooeratinq
bath used for oassivation of zinc workpieces, 1 g/l o r
zinc dust was dissolved in each test solution.
One suc~ test solution without fur;her ad~iti ~ was desisnated
30. as test solution ~.1.1 and served as the contr~l sa~ple. To a second
test solution desianated as 6.1.~ /1 of citric acid and 0;4 ~/1
of l-hydrox~v ethylidene-l,1 diphosphonate ~Nest 2010) was added
as a stabilizing agent. To a third test solu~ion desi~nated
80. 1228~00
as 6.1.3, 1 g/l of citric acid and 0.08 g/l of 1-
hydroxy ethylidene-l,l diphosphonate (Dequest 2010)
was added.
Each test solution was su~jected to agitation at
5. room temperature to simulate typical commercial practice.
The pH at start and finish and the peroxide concentration
measuredin terms of volume percent of 35% hydroqen
peroxide concentrate remaining in the bath was analyzed
over a one-day period. The results are as follows:
10. H`YDROOEN PEROXIDE CONCENTRATION AND cpH
Test Sample
Example 6.1.1 6.1.2 6.1.3
Time H22 pH H22 PH H2G2 ~H
Start 2.56% 1.6 2.95~1.6 3.05% 1.4
15. After 3,5 2.39% - 2,92% - 2.84%
hours
After 21 Oq83% -- 1.72% - 2,37 1.7
hours
After 26 0.50% 2.5 1.42%1.8
hours
20. From the results as set forth in the foregoing
table, it is apparent that control sample 6.1.1 devoid
of any stabilizing agent rapidly lost the peroxide
- oxidizing agent which should be present at a concentration
of at least 2~ by volume to maintain proper passivation
25. treatment. An almost complete replenishment of the
oxidizing agent in Sample 6.1.1 would therefore be
necessary after a period of about one day. In contrast,
sample 6.1.3 exhibited only a small loss of peroxide
after 21 hours while sample 6.1.2 containina a lesser
30. quantity of Dequest 2010 in combination with 1 ~/1 of
8~ 2~00
citric acid also exhibited a sur~rising superiority in
peroxide stability over the control sam~le 6.1.1.
The stabilization of pH is also evident from the
data set forth in the fore~ing table. Control sam~le
5. 6.1.1 rose to a pH level of 2.5 after 26 hours which
would have necessitated the addition of acid to the
operating bath to maintain the pH within the ~referred
operating range of 1.5 to 2Ø On the other hand, both
samples 6.1.2 and 6.1.3 were substantially stable and
10. remained within ontimum pH range over the test duration.
EXAMPLE 6.2
An aqueous stabilizer concentrate was prepared
containing 570 g/l citric acid and 110 ~ hydroxy
15. ethylidene-l,l-diphosphonate (Dequest 2010~. These
operating solutions were prepared as described in
Example 5.1 containing 3% by vol~me Concentrate 6~lA,
3% by volume Concentrate 6.lB, 3% by volume of the
oxidizing concentrate and 1 g/l zinc dust for agln~ the
20. baths. A control sample designated 6.2.1 devoid of
any stabilizing agent had an initial peroxide concentrat-
ion of 3% but after standinq for a period of 18 hours
under the conditions of Example 6.1 had a residual
peroxide concentration of only 1.05% necessitating
25. replenishment. A second test solution desi~nated as
6.2.2 was stabilized by the addition of 2.5 millilitres
/litre of the stabilizer concentrate and had an initial
peroxide concentration of 3~ and after a period of
18 hours had a residual neroxide concentration of 2.43
30. percent.
8~
i22800~:)
EXAMPLE 6.3
In order to evaluate the effectiveness of the
peroxide and pH stabilizing agent of this aspect of
the present invention under actual commercial operation,
5. the stabilizer concentrate as defined in Example 6.2 was
employed for stabilizing a trivalent chromium passivate
solution of a composition similar to the operating bath
of Example 6.1 containing trivalent chromium ions, iron
and cerium ions to provide a pH within the range of about
10. 1.5 to about 2.0 at a temperature of about 70F (21 C)
and containing hydrogen peroxide as the oxidizing agent.
Under normal operation, in the absence of the stahilizer
agent, the commercial operating bath necessitated a replen-
ishment of the peroxide oxidizing agent with the addition
15. of 3% by volume of a 35% hydrogen peroxide concentrate
each morning at the commencement of operation as well as
the addition of another 1% by volume of the peroxide
oxidizing concentrate after about 4 hours operation to
maintain the bath at a minimum of 2~ by volume oxidizin~
20. agent.
By the addition of 1 litre of the stabilizer con-
centrate per one hundred gallons of the operating bath,
the replenishment of the peroxide oxidizing concentrate
was reduced to only a 1% by volume replenishment each
25. operating dav and only a 2% by volume replenishment after
standing over the weekend to restore the bath to a
proper operating condition.
Additionally, the addition of the stabilizer con-
centrate to the operating bath further stabilized the
30. operating p~ over the six day test period wherein the pH
83. 12 2 8 ~o~
remained substantially constant avoiding the necessity
of acid addition to control pH. In contrast, the same
commercial operating bath without any of the stabilizer
concentrate necessitated frequent monitoring of pH and
5. periodic addition o acid to maintain the pH within the
desired range of 1.5 to 2Ø
Bright zinc electroPlated parts processed employing
the foregoing commercial operating bath after aging for
at least 24 hours were subjected to a neutral salt spray
10. corrosion test according to ASTM Procedure B-117. The
excellent corrosion resistancè of the yellow passivate
film was evidenced by the absence of white corrosion
on the parts after 96 hours salt spray testing.
15. EXAMPLE 6.4
The stabilization of a commercial operating bath
of a composition and employing the procedure as
described in Example 6.3 was achiev~d by preparing an
aqueous stabilizer concentraté containing from about 30
20. to about 170 g/l of l-hydroxy ethylidene-l,l diphosphon-
ate (Dequest 2010) in admixture with about 160 to about
500 g/l of citric acid. The stabilizing concentrate was
added to the commercial operating bath to provide an
operating concentration of the l-hydroxy ethYlidene-l,l
25. diphosphonate in an amount of about 0.05 to about 3 g/l
and an operating concentration of the citric acid
constituent of about 0.1 to about 10 g/l. Results
obtained are similar to those as described in Example 6.3.
30.
84. 1228~00
EXAMPLE 6.5
. _ _
An operating bath suitable for depositing a
yellow passivate film on a receptive substrate was
provided by forming a concentrate designated as
5. "Concentrate 6.5A" having a composition as follows:
CONCENTRATE 6.5A
Ingredient Concentrat-ion g/l
HN03(100~) 60
10. H2S04 r100%) 30
Fe2(S04)3 - 25
FeC13 5
Diphosphonate* - 8.5
Citric acid 36
15. Ce 120
*Dequest 201C
An operating bath was prepared comprising 3% by
volume of the chromium ion concentr~te 6.lA o~ Example
6.1, 3~ by volume of concentrate 6.~A and 3% bv volume
20. of the oxidi~ing agent concentrate containing about 35%
hydrogen peroxide.
Steel test panels were subjected to an alkaline
non-cyanide electroplating step to deposit a zinc
plating thereon after which they were thoroughly water
25. rinsed and immersed with agitation in the passivate
operating bath ~or a period of about 30 secon~s at a
temperature of about 70F (21 C) and at a pH ranginq
from about 1.5 to about 2Ø The test panels were there-
after extracted from the o~erating bath and were dried
30. with recirculating warm air.
~ 22800~:)
85.
The test panels after drying were visually
inspected and were observed to have a uniform clear
yellow passivate film thereover. The small addition
of ferric chloxide to the operating bath provides an
5. improvement in the colour intensity of the yellow
passivate film in comparison to that obtained employing
the passivate operating bath of Example 6.1.
The test panels after aging were subjected to
a neutral salt spray test in accordance with the pro-
10. cedure described in Example 6.3 and similar results wereobtained.
ExAMæLE 7.1
An operating bath suitable for depositing a
15. yellow passivate film on a receptive substrate was made
up as follows: A trivalent chromium containing concentrate
designated as "Concentrate 7.1A" having a compositlon
was first made up as follows:
20. CONCENTRAIE7.lA
Ingredient Concentration g/l
Cr . 25
- Ferric ammonium sulphate 30
Sodium chloride 20
25. Nitric acid (100%) 60
Succinic acid 20
A cerium ion concentrate 7.lB was provided con-
taining about 80 g/l ceric ions in the form of ceric
sulphate in a dilute (about 5~) sulphuric acid solution.
30. An oxidizing agent concentrate was also provided con-
86. 1228~0~
taining about 35~ hydrogen peroxide.
A yellow passivate operating bath wasprepared com~rising water containing 2% by volumè of
Concentrate7.lA, 2% by volume of the cerium ion concen-
5. trate7.lB and 2~ by volume of the oxidizing agentconcentrate 7,lC.
An aqueous silicate rinse solution was ~rovided
containinq 10 q/1 sodium silicate calculated as SiO2.
Steel test ~anels were subjected to an alkaline,
10. non-cyanide electroplating step to deposit a zinc plating
thereon after which they were thoroughly water rinsed
and immersed with agitation in the passivate 02eratina
bath for a period of about 30 seconds at a temperature
of about 70F (21C) and at a pH ranging from about 1~5
15. to about 2Ø The test panels were extracted from the
operating bath, subjected to a tap water rinse and were
thereafter contacted with the silicate rinse solution
for about 30 seconds at a tem~eratulre of about 70F
(21 ~). The silicate rinsed-test ~anels were thereafter
20. extracted from the rinse solution and were dried with
recirculating warm air.
The test panels after drying were visually
ins~ected and were observed to have a very hard clear
yellow ~assivate film. The test ~anels after aging for
25. at least 24 hours, were subjected to a neutral salt
spray corrosion test according to AST~ Procedure B-117.
The test panels treated in accordance with the present
process exhibited excellent salt sprav resistance after
exposure for a period of more than 96 hours.
30.
12Z8~0~)
87.
EXAMPLES 7.2.1 to 7.2.14
A series of trivalent chromium containina
concentrates was prepared suitable for dilution with
water to make up an operating bath in further combination
5, with an oxidizing agent and cerium or lanthanum ions
as follows:
CoNcENTRATE 7.2A
10. Ingredient Concentration, g/l
Cr 24
4 7H20 25
Ferrous ammonium sulFhate 12
15. Sodium Fluoroborate 15
Succinic acid 25
Mitric acid (100%~ 60
CONCENTRATE 7.2B
Ingredient Concentration, g/l
Cr 24
NaCl 20
25. Ferrous ammonium sulphate 25
Sodium succinate 55
Nitric acid (100%) 60
122800~)
CONCENTRATE 7.2C
Ingredient Concentration, g/l
Cr+3 24
5- Ferric ammonium sulphate 50
Sodium succinate 55
NaCl 20
Nitric acid (100%) 60
10.
CONCENTRATE 7.2D
Ingredient Concentration, g/l
Cr+3 24
15. Ferric ammonium sulphate 50
Succinic acid 25
NaCl I 20
Nitric acid (100%) 60
20.
CONCENTRATE7.2E
Ingredient Concentration, g/l
Cr~3 24
25. Ferric ammonium sulphate 50
NaCl 20
Malonic acid 25
Nitric acid (100~) 60
30.
89. ~28000
CONCENTRATE 7.2F
Ingredient Concentration, g/l
Cr~3 24
5. Fe2(S04)3 30
NaC1 20
Gluconic acid 20
Nitric acid (100%) 60
10 . __ .
CONCENTRATE 7.2G
. . _
Ingredient Concentration, g/l
Cr+3 24
15. Ferric ammonium sulphate 50
NaC1 20
Maleic acid ~ 25
Nitric acid (100%) 60
20.
A cerium ion concentra.~ was ~rovided containing
about 80 y/l ceric ions in the form of ceric sulphate in
a dilute sulphuric acid solution. An oxidizing agent
con~ntrate was also provided containing about 35% hydrogen
25. peroxide. A series of operating baths (Exam~les 7.2.1 to
`1.2.7) were prePared suitable for forming a vellow
passivate film on a substrate each containina 2% by
volume of the cerium ion concentrate, 2~ by volume of
the oxidizing agen.t concentratel and 2% by volume of
30. one of the chromium concentrates 7.2A to 7.2G resDectively.
90. 122800~
A lanthanum ion concentrate was provided
containing about 60 g/l lanthanum ions in the form of
a solution of lanthanum chloride. An oxidizing agent
concentrate was also provided containing about 35%
5. hydrogen peroxide. A series of ooerating baths (Examples
7.2.8 to 7.2.14) were prepared suitable for fol~ing a
blue-bright passivate film on a substrate each containing
2% by volume of the lanthanum ion concentrate, 2% by
volume of the oxidizing agent concentrate, and 2% by
10. volume of one of the chromium concentrates 7.2A to
7.2G respectively.
Zinc plated steel test panels as described in
Example 7.1 were processed through each of the operating
baths (Examples 7.2.1 to 7.2.14) under the conditions
15. as set forth in Example 7.1 whereafter the passi~ated
panels were subjected to a silicate post~rinse treatment
employing an aqueous silicate rinse solution in which
the silicate concentration was varied from about 1 to
about 40 g/l calculated as SiO2 at temperatures ranging
20. from 50 to 150F (10 to 66C). The panels were
subsequently air dried and subjected to a neutral salt
spray corrosion test as described în Example 7,l.
Similar results to those reported for Example I.l were
obtained.
25.
EX~PLES 7.3.1 to 7.3.6
A series of operating baths was prepared as
follows:
30.
gl. 1228~)0~)
- OPERATING BATH 7.3A
Ingredient Concentration, g/l
Cr2(S04)3 2.2
5- NH4HF2 .18
H2S04 1.2
22 5.3
FeNH4S4* 0.25
10. 4 7H20 1.6
*Ferrous Ammonium Su~hate= Fe(S04)-(NH4)2S04 6H20
OPERATING BATH7 3B
Ingredient Concentration, g/~
15. Cr2(So4)3 5.6 --
NH4HF2 0 4
H2S04 2.7
20. ~22 5.3
4 4 0.58
Cos04-7H2o 3 75
OPERATING BATH 7.3C
25. Ingredient Concentration, g/l
Cr2(S04)3 3.0
4 2 0.24
2 4 1.54
22 5.3
4S04 0.25
4S04 2.1
*Nickel Ammonium Su~phate= NiSo4-(NH4)2So4-6H2o
12~8~)00
OPERATING BATH 7.3D
_
IngredientConcentratlon, g~l
2(SO4)3 3,o
4 2 0.24
2S4 1.54
4SO4 Q.24
H22 5.3
lO. 4 H2O 1.0
OPERATING BATH7.3E
IngredientConcentration, g/l
15. 2(SO4)3 3.0
4 2 0.24
H2SO4 1.54
FeN~4'S4 0.24
20. 2 2 ;~3
H2M~o4 H20 1. O
OPERATING BATH 7. 3F
25. In~_edientConcentration, g/l
Cr2(So4)3 3.0
4 2 0.24
H2SO4 1.54
30. FeNH4S4 0.24
2 2 5'3
(~H4)4(NiMoo24H6)4.4H2o 1.0
1~2~3~00
93.
Zinc plated test panels prepared as previously
described in Example 1 were processed through the
foregoing operating baths (Exam~les 7.3.1 to 7.3.6~
under the conditions previously described in Example 7.1
5. whereafter they were water rinsed and subjected to an
aqueous silicate post~rinse treatment in a rinse solution
in which the silicate concentration calculated as SiO2
was varied from about 1 to about 40 g/l at temperatures
ranging from about 50 to about 150F (10 to 66C).
10. The passivated and post rinsed panels after drying were
subjected to salt spray tests as described in Example 7.1
and similar results were ohtained.
