Note: Descriptions are shown in the official language in which they were submitted.
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Description
FINELY CRYSTALLINE AND/OR FAST PHOSPHATE CONVERSION
COATING COMPOSITION AND PROCESS
BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to compositions and processes for depositing zinc phos-
phate cont~ining conversion co~ting~ on metal surfaces, particularly the surfaces of iron,
steel, zinc-iron alloy, galvanized steel and other predominantly zinciferous surfaces, and
al.l",;"~l", anditsalloysthatcontainatleast45 %byweightofalllminllm Theinventionparticularly relates to such compositions and processes that produce, at a high coating
speed, a conversion coating with a very fine average crystal size.
Statement of Related Art
The general process of zinc phosphate conversion coating is well known in the
art. See, e.g., M. ~.qm~her, "Ecologically Safe Pretre~tment~ of Metal Surfaces", Hen-
kel-Referate 30 (1994), pp. 138 - 143, which, except to the extent that it may be contrary
to any explicit st~tem~nt herein, is hereby incol~uldl~d herein by reference. In brief, con-
tact of active metals with aqueous acidic compositions cont~inin~ zinc and phosphate
ions results in the deposition on the active metal sllrf~es of a conversion coating con-
taining zinc phosphate. If the active metal is ferrous, iron phosphates are usually includ-
ed in the coating, and in modern practice nickel andtor m~ng~nese are often included in
the coating composition and thereby in the coating formed. In order to speed the process
and improve the uniformity of the coating, it is c~Lolll~y to include in the coating com-
position a component called an "accelerator" that does not usually become incorporated
into the coating formed. Typical widely used accelerators include nitrate, nitrite, and
chlorate ions, water soluble niLloal~ollldLic organic compounds such as p-nitrobenzene sul-
fonic acid, and hydroxylamine (the latter almost always in the form of salts or complex-
es).
~, 25 A frequently observed problem with prior art conversion coatings, particularly
on cold rolled steel, has been the production of small rusty spots on areas of the treated
~ul~Lldl~ metal that were blocked from full contact with the conversion coating forming
liquid composition by small gas bubbles that were formed andtor trapped on the substrate
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surface during the conversion coating treatment process. It is believed that the water
vapor inside such bubbles is sufficient to cause rusting before the desired formation of
a protective conversion coating can progress sufficiently far to prevent rust, and once a
rusty spot has formed, it can not usually be covered satisfactorily later even by full con-
5 tact with the conversion coating forming liquid composition.
DF!~CRIPTION OF THE INVENTION
Object of the Invention
One object of this invention is to provide a composition and process for phosphat-
ing that will provide a protective conversion coating with a more refined crystal size than
10 is now generally achieved by zinc phosphating. Another ~It~rn~tive or concurrent object
is to provide a zinc phosphating composition and process that will form a high quality
protective conversion coating during a brief contact time with a metal substrate to be
coated, so that coil coating and other continuous phosphating operations can be run at
higher speeds. Still another concurrent or alternative object is to avoid the formation of
5 surface rust on small areas of the treated substrate that are blocked by gas bubbles from
full contact with the conversion coating solution. Other objects will be apparent from
the description below.
General Principles of Description
Except in the claims and the operating examples, or where otherwise expressly
20 indicated, all numerical quantities in this description indicating amounts of material or
conditions of reaction and/or use are to be understood as modified by the word "about"
in describing the broadest scope of the invention. Practice within the numerical limits
stated is generally preferred, however. Also, throughout the description and claims,
unless expressly stated to the contrary: percent, "parts of', and ratio values are by weight;
25 the description of a group or class of materials as suitable or pler~ d for a given
purpose in connection with the invention implies that mixtures of any two or more of the
members of the group or class are equally suitable or ~ler~ d; description of
constituents in chemical terms refers to the con~tit~l.ont~ at the time of addition to any
combination specified in the description, and does not necessarily preclude chemical
30 interactions among the constituents of a mixture once mixed; specification of materials
in ionic form implies the presence of sufficient counterions to produce electrical
neutrality for the composition as a whole; any counterions thus implicitly specified
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should preferably be selected from among other con~tit lent~ explicitly specified in ionic
form, to the extent possible; otherwise such counterions may be freely selected, except
for avoiding counterions that act adversely to the objects of the invention; the terms
~ "molecule" and "mole" and their gr~mm~tiç~l variations may be applied to ionic,
elem~nt~l, or any other type of chemical entities defined by the number of atoms of each
type present therein, as well as to substances with well-defined neutral molecules; the
first definition of an acronym or other abbreviation applies to all subsequent uses herein
of the saTne abbreviation; and the term "polymer" includes "oligomer", "homopolymer",
"copolyrner", "terpolymer", and the like.
Sllmm~ry of the Invention
It has been found that one or more of the objects stated above for the inventioncan be achieved by the use of a conversion coating forming aqueous liquid composition
that comprises, preferably consists eesçnti~lly of, or more preferably consists of, water
and:
15 (A) dissolved zinc cations;
(B) dissolved phosphate anions;
(C) a dissolved component selected from the group consisting of organic acids and
anions thereof that (i) contain at least two moieties per molecule that are selected
from the group consisting of carboxyl and carboxylate moieties and hydroxyl
moieties that are not part of a carboxyl moiety and (ii) do not contain more than
12 carbon atoms per molecule; and
(D) a dissolved component selected from the group con~i~ting of polymer molecules
which contain more than 12 atoms per molecule and in which at least 50 % of the
polymer molecule is made up of one or more moieties with one of the formulas:
CH3
-(CHz-CH)- or -(CHz-C)-,
C=O C=O
1 l
OM OM
where M l~.ese~ a hydrogen atom, a monovalent cation, or a monovalent frac-
tion of a polyvalent cation; and, optionally,
(E) a component of dissolved metal cations selected from the group consisting of
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metal cations, exclusive of zinc cations, with a charge of at least two;
(F) a component of dissolved accelerator molecules, exclusive of any molecules that
are part of any of the prececling components; and
(G) a component of dissolved simple and/or complex fluoride anions, exclusive of
any anions that are part of any of the preceAin~ components.
Various embo-liment~ of the invention include working compositions for direct
use in treating metals, make-up conr~ntr~t~s from which such working compositions can
be ~l~paled by dilution with water, replenisher concentrates suitable for m~int~inin~ op
timum performance of working compositions according to the invention, processes for
treating metals with a composition according to the invention, and extended processes
including additional steps that are conventional per se, such as cleaning, activation with
titaniurn phosphate sols (Jernstedt salts), rinsing, and subsequent painting or some similar
overcoating process that puts into place an organic binder cont~ining protective coating
over the metal surface treated according to a ,l~lv~l embodiment of the invention. Art-
icles of manufacture including surfaces treated according to a process of the invention
are also within the scope of the invention.
Description of Preferred Embodiments
For a variety of reasons, it is sometimes l~lc;rcll~,d that compositions according
to the invention as defined above should be sub~ lly free from many ingredients used
in compositions for similar purposes in the prior art. Specifically, when maximum stor-
age stability of a concentrate is desired, it is preferred, with increasing ~l~r~,.ellce in the
order given, independently for each preferably minimi7ed component listed below, that
these compositions contain no more than 25, 15, 9, 5, 3, 1.0, 0.35, 0.10, 0.08, 0.04, 0.02,
0.01, 0.001, or 0.0002, percent of each of the following constituents: nitrite, chlorate,
chloride, bromide, iodide, organic compounds cont~inin~ nitro groups, hexavalentchromium, m~n~nPse in a valence state of four or greater, ferricyanide; ferrocyanide,
and pyrazole compounds. ln contrast, in working solutions, accelerator components
such as those included in this list have no known detrimental effect (except for the danger
of white specking zinciferous surfaces treated with compositions that contain too much
chloride, which is formed in situ from chlorate), but are generally not needed, and their
absence may therefore be preferred for economic reasons.
The dissolved zinc cations required for nPcPc~ry component (A) may be obtained
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from any soluble zinc salt or from zinc metal itself or any zinc co~ g compound that
reacts with aqueous acid to form dissolved zinc cations. Normally ~lcrcll~,d sources,
largely for economic reasons, are zinc oxide, zinc carbonate, and zinc dihydrogen phos-
phate. In a working conversion coating forming aqueous liquid composition according
5 to the invention, the concentration of dissolved zinc cations preferably is at least, with
increasing plcrclcnce in the order given, 0.1, 0.2, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.85,
0.90, 0.95, 0.98, or 1.00 parts per thousand (hereinafter usually abbreviated as "ppt") and
independently preferably is not more than, with increasing plt;r~cllce in the order given,
2.0, 1.8, 1.6, 1.4, 1.30, 1.20, l.lS, or 1.10 ppt.
The dissolved phosphate ions that constitute necessary component (B) also may
be obtained from a variety of sources as known in the general phosphate conversion coat-
ing art. Because of a preference noted below for a substantial amount of total acid in a
working conversion coating forming aqueous liquid composition according to the inven-
tion, normally much of the phosphate ion content will preferably be supplied by phos-
phoric acid added to the composition, and the stoichiometric equivalent as phosphate ions
of all undissociated phosphoric acid and all its anionic ionization products in solution,
along with the stoichiometric equivalent as phosphate ions of any dihydrogen phosphate,
monohydrogen phosphate, or completely neutralized phosphate ions added to the compo-
sition in salt form, are to be understood as forming part of component (B), irrespective
of the actual degree of ionization that exists in the composition. In a working conversion
coating forming aqueous liquid composition according to the invention, the concentration
of component (B) preferably is at least, with increasing preference in the order given, 5,
6, 7, 8, 9, 10, 10.5, 11.0, 11.5, 11.9, 12.2, 12.4, 12.6, 12.8, 13.0, 13.2, 13.4, or 13.6 ppt
and independently preferably is not more than, with increasing plefe,~llce in the order
given, 100, 50, 40, 30, 27, 24, 21, 19, 18, 17, 16.5, 16.0, 15.5, 15.0, 14.5, 14.3, 14.1,
13.9, or 13.7 ppt.
Independently of the other preferences, the ratio of the concentration of compon-
ent (A) to the concentration of component (B) in a conversion coating forming aqueous
liquid composition according to the invention, whether working or concentrate, preferab-
ly iS at least, with increasing preference in the order given, 1.0:50, 1.0:40, 1.0:35, 1.0:30,
1.0:27, 1.0:24, 1.0:21, 1.0:18, 1.0:16, 1.0:15, 1.0:14, or 1.0:13.7 and independently pref-
erably is not more than, with increasing l~lcfclence in the order given, 1.0:5.0, 1.0:6.0,
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1.0:7.0,1.0:8.0,1.0:8.5,1.0:9.0,1.0:9.5,1.0:10,1.0:10.5,1.0:11.0,1.0:11.5,1.0:12.0,
1.0:12.5, 1.0:13.0, or 1.0:13.3.
Component (C) is preferably derived from anions or other molecules each of
which contains both at least one carboxyl(ate) moiety and one hydroxyl moiety that is
not part of any carboxyl(ate) moiety, more preferably from the group con~icting of citric
acid, gluconic acid, and heptogluconic acid and the water soluble salts of all of these
acids, most preferably from citric acid and its water soluble salts. Independently, the
concentration of component (C) in a working conversion coating forming aqueous liquid
composition according to the invention preferably is at least, with increasing preference
0 in the order given, 0.1, 0.2, 0.3, or 0.4 millimoles per kilogram of total composition
(hereinafter usually abbreviated "mM/kg") and, if small crystal size of the conversion
coating formed is desired, more preferably is at least, with increasing preference in the
order given, 1.0, 1.2, or 1.6 mM/kg; if small crystal size of the conversion coating formed
is desired and the concentration of component (D) is near the lower end of its preferred
ranges as further described below, the con~entr~tion of component (C) in a working con-
version coating forming aqueous liquid composition according to the invention still more
preferably is at least 3.5 mM/kg. Independently, primarily for reasons of economy, the
concentration of component (C) in a working composition according to the invention
preferably is not more than, with increasing l~lcrelGllce in the order given, 50, 25, lS, 10,
7,5, 4.5, or 4.1 mM/kg, and if larger crystal size is acceptable, more preferably is not
greater than, with increasing ~rt;rc~ ce in the order given, 3.2, 3.0, 2.8, 2.5, 2.2,1.9, or
1.7 mM/kg.
Component (D) preferably is selected from polymer molecules in which at least,
with increasing p~crclcnce in the order given, 60, 70,75,80, 85, 90, or 95 % of the mole-
2s cule consists of one or more moieties with one of the formulas:
fH3
-(CH2-fH)- or -(CH2-f)-,
f=o f=o
OM OM
more preferably the formula shown on the left, or in other words, acrylate rather than
methacrylate moieties. Independently, with increasing ~ler~rcllce in the order given, at
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least 30, 50, 60, 70, or 80 nurnber percent of these acrylate and methacrylate moieties in
component (D) have hydrogen rather than any other atom or cation in the position in the
formula indicated by the symbol "M" in the formulas shown. Independently of bothother plcrc,cl,ces, the weight average molecular weight of the polymers in the component
5 (D), measured as its stoichiometric equivalent when all the acrylate and methacrylate
moieties are in an acid form, preferably is at least, with increasing pLc;rcl~ ce in the order
given, at least 400, 500, 600, 700, 750, 800, 850, 900, 950, or 975 and independently
preferably is not more than, with increasing ~lcrclcnce in the order given, 10,000, 9000,
8000, 7000, 6000, 5000, 4500, 4000, 3500, 3000, 2500, 2000, 1700, 1400, 1300, 1250,
1200, 1 150, 1 100, or 1050. Also, independently of the other preferences for component
(D), the concentration of component (D) in a working conversion coating forming aque-
ous liquid composition according to the invention preferably is at least 5, 10, 15, 20, 22,
or 24 ppm and independently preferably is not more than 300, 200, 100, 85, 75, 65, or
55 ppm and, unless the concentration of component (C) is not more than 0.4 mM/kg,
15 more preferably is not more than, with increasing preference in the order given, 45, 35,
30, or 26 ppm.
If high corrosion resistance after application of an organic protective coating to
a metal substrate, subsequent to forming a conversion coating thereon by cont~cfinP: the
substrate with a working conversion coating forming aqueous liquid composition accord-
ing to the invention, is desired, as it usually is, a working conversion coating formingaqueous liquid composition according to the invention preferably contains one or more
metal ions selected from optional component (E). Examples of preferred combinations
of zinc ions with metal ions of component (E) in a working conversion coating forming
aqueous liquid composition according to the invention are: Zn and Mn; Zn, Mn, and Co;
25 Zn, Mn, and Cu; Zn and Cu; Zn, Co, and Cu; and Zn, Mn, and Ni. It is especially pre-
ferred for a working conversion coating forming aqueous liquid composition according
to the invention to contain, as at least part of optional component (E), dissolved divalent
m~n~nese cations in a concentration that preferably is at least, with increasing prefer-
ence in the order given, 100, 200, 300, 400, 500, 550, 600, 650, 700, 750, 800, 825, or
30 835 ppm and independently preferably is, primarily for reasons of economy, not more
than, with h~ ca,h~g ~,crt;,cllce in the order given, 4000, 3000, 2000, 1500, 1400, 1300,
1250, 1200, 1150, 1100, 1050, 1000, 950, or 900 ppm. Also, independently ofthe prefer-
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ences for m~n~n.oce as noted, it is especially preferred for a working conversion coating
forming aqueous liquid composition according to the invention to include, as at least part
of optional component (E), dissolved divalent nickel cations in a concentration that pref-
erably is at least, with increasing preference in the order given, 100, 200, 300, 400, 500,
550, 600, 650, 700, 750, 765, 785, or 790 ppm and independently preferably is, primarily
for reasons of economy, not more than, with increasing preference in the order given7
4000, 3000, 2000, 1500, 1400, 1300, 1250, 1200, 1150, 1100, 1050, 1000, 950, 900, or
850 ppm.
Independently of other pr~fe~ ces, the ratio of the concentration of zinc cations
to the sum of the concentrations of m~nganese and nickel cations in a conversion coating
forming aqueous liquid composition according to the invention preferably is at least, with
increasingpl~ ce in the order given,1.0:5.0, 1.0:4.0, 1.0:3.5, 1.0:3.0, 1.0:2.5, 1.0:2.3,
1.0:2.1, 1.0:1.9, 1.0: 1.7, or 1.0: 1.6 and independently preferably is not more than, with
increasingpreferenceintheordergiven, 1.0:0.2, 1.0:0.4, 1.0:0.6, 1.0:0.8, l.0:1.0, l.0:1.1,
s 1.0:1.2, 1.0:1.3, 1.0:1.4, or 1.0:1.5. Independently, when both m~n~nese and nickel are
present in a conversion coating forming aqueous liquid composition according to the in-
vention, the ratio of m~ng7ln~se to nickel preferably is at least, with increasing plerelellce
in the order given, 1.0:2.0, 1.0:1.7, 1.0: 1.5, 1.0:1.3, 1 .0 : 1.2, 1.0: 1.1, or 1.0: 1.0 and inde-
pendently preferably is not more than, with increasing ~rerclcnce in the order given,
1.0:0.2, 1.0:0.5, 1.0:0.7, 1.0:0.8, or l.0:0.9.
A working conversion coating forming aqueous liquid composition according to
the invention preferably includes, as at least part, and more preferably as all, of optional
component (F) a dissolved source of hydroxylamine. The source may be hydroxylamine
itself, but most users prefer to avoid potential hazards from hzln~lling pure hydroxylamne,
So that a salt or complex of hydroxylamine is generally preferred. Hydroxylamine sul-
fate, which has the chemical formula (NH30H)2SO4 is particularly preferred for economy
and lack of any ions that may be deleterious to the quality of conversion coating forrned,
e.g., chloride ions, which may induce white speçkin~ of any zinc-rich areas of the coated
substrate. Irrespective of its actual source, the concentration in a working conversion
coating forming aqueous liquid composition according to the invention, measured as its
stoichiometric equivalent as pure hydroxylamine, preferably is at least, with increasing
pl~r~,lcllce in the order given, 0.2, 0.5, 0.8, l .0, 1.1, 1.2, 1.3, 1.4, or 1.5 ppt and independ-
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ently preferably is not more than, with increasing plcr~l~nce in the order given, 5, 4, 3.5,
3.0, 2.5, 2.3, 2.1, 1.9, or 1.8 ppt.
If the surface of the substrate to be conversion coated according to this invention
includes a portion that contains at least 45 % of al~ l l and/or a portion that contains
5 at least 85 % of zinc, a working conversion coating forming aqueous liquid composition
according to the invention preferably includes optional simple and/or complex fluoride
anions component (G); more preferably, if the substrate surface includes a portion that
contains at least 85 % of zinc, at least part of the fluoride present is in the form of fluo-
boric, fluosilicic, fluotitanic, and/or fluozirconic acids and their salts, most preferably
10 fluosilicic acid and/or fluosilicate ions.
Because of the competing complex-forming-and-dissociating equilibria in which
fluoride can participate in a working conversion coating forming aqueous liquid compo-
sition according to this invention that contains some deliberately added complex fluomet-
allate and/or hydrofluoric acid, the plcr~lable concentrations for fluoride in such a com-
position are specified in terms of "active free fluoride", as measured by means of a fluor-
ide sensitive electrode and associated instrl-ment:~tion and methods that are described in
U. S. Patents 3,350,284 and 3,619,300. Suitable ~a.dL~Is and instructions for using it
are commercially available under the name LINEGUARD(~ l O lA Meter from the Parker
~mchem Division ("PAM") of Henkel Corp., Madison Heights, MI. "Active free fluori-
20 de" as this term is used herein was measured relative to a 120E Activity Standard So-
lution also commercially available from PAM. In brief, the fluoride sensitive electrode
and the reference electrode provided with the LINEGUARD(~) 101 A Meter are both im-
mersed in the noted Standard Solution and the millivolt meter reading is adjusted to 0
with a Standard Knob on the instrument, after waiting if necessary for any drift in read-
25 ings to abate. The electrodes are then rinsed with deionized or distilled water, dried, andimmersed in the sample to be measured, which should be brought to the same temper-
ature as the noted Standard Solution had when it was used to set the meter reading to 0.
The reading of the electrodes immersed in the sample is taken directly from the millivolt
(hereinafter often abbreviated "mv" or "mV") meter on the instrument and converted to
30 ppm by comparison with the millivolt readings obtained with solutions of known free
fluoride content, usually sodium or potassium fluoride solutions in water.
The free fluoride content of a working conversion coating forming aqueous liquid
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composition according to the invention, when a surface including areas that are at least
45 % alll,.,i,,l~,.l is being treated, preferably is at least, with increasing preference in the
order given, 100, 150, 200, 250, 300, 350, 375, or 400 ppm and independently preferably
is not more than, with increasing ~rerelel1ce in the order given, 1200, 1000, 900, 800,
750, 725, 700, 675, 650, 625, or 600 ppm. If a surface including areas that are at least
85 % zinc but no areas that are at least 45 % alllminum is to be treated, the free fluoride
content preferably is not more than, with increasing preference in the order given, 100,
75, 60, 45, 40, 35, 30, 25, 20, 15, or 10 ppm, but the total content of fluoborate, fluosili-
cate, fluotitanate, and fluozirconate, which in~ s the stoichiometric equivalent as these
ions of all corresponding acids and partially acidic salts added to the compositions, ir-
respective of the actual degree of ionization existing in the composition, preferably is at
least, with increasing p,~re~nce in the order given, 0.1, 0.3, 0.5, 0.7, 0.8, 0.9, 1.00, 1.10,
1.15, or 1.20 ppt and independently preferably is, primarily for reasons of economy and
with increasing preference in the order given, not more than 3.0, 2.5, 2.0, 1.8, 1.6, 1.50,
1.45, 1.40, 1.35, or 1.30 ppt. Most preferably, the total amount of these complex fluoride
anions is fluosilicate or its corresponding acid or acid salt. When the surfaces being
treated are ferrous and do not include any areas that are predomin~ntly either al~-minllm
or zinc, fluoride may be omitted altogether, and such omission is normally preferred for
economic reasons. If any fluoride is present in the working compositions according to
the invention for treating only ferrous substrates, the same preferences as noted above
for the maximum amount of free fluoride activity in a composition for treating alumin-
urn-free zinciferous surfaces apply.
In a working conversion coating forming aqueous liquid composition according
to the invention, the Total Acid and Free Acid contents of the composition are preferably
measured and controlled. These acid contents, consistent with general practice in the
phosphating art, are ~re~,st:d herein in "points", by which is meant the millilit~rs ("ml")
of 0.1 ~NaOH required to titrate a 10 ml aliquot sample, to a pH of 8.2 (e.g., with phe-
nolphthalein indicator) for Total Acid and to a pH of 3.8 (e.g., with bromophenol blue
indicator) for ~ree Acid.
In a working conversion coating forming aqueous liquid composition according
to the invention, the content of Free Acid preferably is at least, with increasing prefer-
ence in the order given, 0.1, 0.2, 0.3. 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1.0 points and inde-
.
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pendently preferably is not more than, with increasing preference in the order given, 3.0,
2.5, 2.0, 1.8, 1.7, 1.6, or 1.5 points; and, independently, the content of Total Acid prefer-
ably is at least, with increasing preference in the order given, 15, 16, 17, 18, 19, 20, or
21 points and independently preferably is not more than, with increasing preference in
s the order given, 50, 40, 35, 32, 30, 29, or 28 points. The Free Acid and Total Acid con-
tents can be adjusted into the ~.crcl.ed range, without disturbing the preferred values for
other constituents of a conversion coating forming aqueous liquid composition according
to the invention, by additions, to an otherwise satisfactory conversion coating forming
aqueous liquid composition, of small amounts of strongly zllk~lin~ m~t~ri~l~ such as sodi-
um and potassium hydroxides or strong acids such as nitric and sulfuric acids? as appro-
priate for the direction in which it is desired to change the Free Acid and Total Acid con-
tents, in a manner generally known to those skilled in the art.
Preferably make-up concentrate compositions according to this invention are
single package liquid cunccllL ~les, i.e., are aqueous liquids that consist of water and each
of components (A) through (G), as recited above for working compositions, that are de-
sired in the working compositions to be prepared from the make-up concentrate composi-
tions, along with any other ingredients desired in the working compositions, except pos-
sibly for strong acids or alkalies that are not part of any of components (A) through (G)
and are added to working compositions after ~ Lion thereof to slightly less than the
final desired volume, in order to adjust the Free Acid and Total Acid contents therein
as defined above. Preferably, all the components except water of a make-up concentrate
composition according to the invention are present therein in a concentration such that
the ratio of the concentration of each component in the make-up concentrate composi-
tion to the concentration of the same component in the working composition that it is de-
sired to prepare from the concentrate composition will be at least, with increasing prefer-
ence in the order given, 5:1.0, 10:1.0, 20:1.0, 30:1.0, 40:1.0, or 50:1Ø
Preferably the conccl,ll~lcs are stable to storage in the temperature range from at
least -20 to 50, or more preferably to 80, ~ C. Stability may conveniently be evaluated
by measuring the free acid and total acid contents as described above. If these values
have not changed after storage by more than 10 % of their value before storage, the con-
centrate is considered storage stable. With increasing plcrcle,lce in the order given, the
concentrates according to the invention will be storage stable as thus defined after stor-
11
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W O 97/17480 PCT~US96/17086
age for 1, 3, 10, 30, 60, or 200 days.
The actual conversion coating forming step in a process according to this
invention preferably is performed at a temperature that is at least, with increasing
preference in the order given, 35, 38, 41, 44, 46, or 48 ~C and independently preferably
iS, primarily for reasons of economy, not more than 70, 65, 60, 55, 53, 51, or 50 ~C.
Primarily for reasons of economy, the time of contact between the metal surface being
coated and a working composition according to the invention preferably is not greater
than, with increasing ~ el,ce in the order given, 200, 150, 120, 100, 80, 70, 60, 50,
40, 30, 25, 20, 17, 14, 11, 9.0, 7.0, 5.0, 4.0, 3.0, or 2.0 seconds, if a uniform and
adequately protective coating is formed within that time. Otherwise, a process according
to this invention is preferably operated under the conditions conventional in the art for
compositions that are otherwise like the compositions according to this invention, except
for substit~lting a conventional amount of nitrite accelerator for all of the hydroxylamine,
acrylate and/or methacrylate polyrner, and at least difunctional acids and/or hydroxyacids
described above for compositions according to this invention. Furthermore, in a process
according to the invention that includes other steps than zinc phosphate conversion
coating with a composition as described above, the other steps preferably are conven-
tional per se.
The practice of this invention may be further appreciated by consideration of the
following, non-limiting, working exarnples and comparison examples.
General Processin~ Conditions
The substrates used and their abbreviations as used in later tables are shown inTable I below. The ~ub~lldles were in the form of conventional rectangular test panels.
The processing sequence used is shown in Table 2 and its notes. All materials
identified by one of the tr~ m~rk~ DEOXYLYTE(~), FIXODl!NE(~), or PARCO(I~ are
commercially available from the Parker Amchem Division of Henkel Corp., Madison
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Table 1
Substrate Metal Type Abbreviation
Cold rolled steel CRS
5One side electrogalvanized steel lEG
Hot dip galvanized steel HDG
Both sides electrogalvanized steel 2EG
Zinc-iron alloy Z-I
Table 2
rrocess ActionFluid Used Temp., ~C Time, Sec.
SprayPrimaryCleaning21 g/LofPARCO@) 49 90
Cleaner 1502 in water
Spray Rinse Tap Water 49 30
Activation FIXODINE~) Z-8 20-25 30
Conditioner, 11 ppm Ti
Phosphating See latertables 49 10, 120*
Spray Rinse Tap Water 20 - 25 30
Postrinsing 0.25 % DEOXYLYTE~ 20-25 30
54 NC Postrinse in water
SprayRinse Deionized water 20-25 15
Footnote for Table 2
*The entire panel was dipped into the ph~sphz~ting composition for 10 seconds. Then the
top half of the panel was withdrawn. The bottom half remained immersed for a total of
120 seconds, and the entire panel was then withdrawn from contact with the phosphating
composition.
Abbreviations for Table 2
Temp. = Temperature; Sec. = Seconds.
Heights, Michigan and/or Henkel Metallchimie, Dusseldorf, Germany, together with di-
rections for using them as noted below.
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Workin~ Phosphatin~ Compositions
The most important components of several working compositions are shown in
Table 3; the balance not shown in the table is water or counterions, the latter being pre-
dominzln~ly sodiurn to serve as counterions to a substantial fraction of the phosphate
content. Aqueous sodium hydroxide solution was used when needed to lower free acid
content. Nitric acid was added in small quantities as the concentration of citrate was in-
creased, to avoid unwanted decreases in free acid content without chz~ngin~ the zinc to
phosphate ratio. Any free fluoride content indicated in the Table by a specific number
was measured by a fluoride sensitive electrode in the manner described above and was
added as hydrofluoric acid. Free fluoride contents preceded by the "less than" sign (<)
10 were measured in the same way, but also mean that no hydrofluoric acid or other known
source of uncomplexed fluoride was deliberately added; the free fluoride activity presum-
ably arose from small concentrations of hydrofluoric acid known to exist in the fluosilicic
acid that was deliberately added. The source of the acrylate polymer shown in Table 3
was AcusolTM 410 polymer solution in water, a product commercially supplied by Rohm
15 & Haas Co. and reported by its supplier to contain 54 % by weight of a homopolymer of
acrylic acid in which 20 number % of the carboxylic moieties are neutralized with
sodium hydroxide, the polymer in the all acid form having a weight average molecular
weight of 1000 and a number average molecular weight of 650.
14
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Table 3
Ingredient and Amount of Ingredient in Composition FY5~ r~ Number:
C L ~
Unit 1 2 3 4 5 6 7 8 9 10
Zn+2 ions, ppt 1.1 1.1 1.11.1 1.05 1.1 1.1 1.01
Po4-3 ions, ppt 14 14 14 14 13.7 14 14 13.7 14 14
Mn+2 ions, ppt 0.8 0.8 0.80.8 0.81 0.8 0.8 0.84 0.8 0.8
Nj+2 ions, ppt 0.8 0.8 0.80.8 0.78 0.8 0.8 0.8 0.8 0.8
Sodiumcitrate Slt.Slt. Slt. Slt. Slt. Slt. Slt. Slt. Slt. Slt.
dihydrate, ppt
(NH3OH)2SO4,1.7 1.7 1.7 1.71.7 1.7 1.7 1.7 1.7 1.7
ppt
Free Acid, 1.5 1.7 1.0 1.01.0 1.0 1.5 1.0 0.7 0.6
points
Total Acid, 27 28 27 21 25 27 27 26 27 27
points
Acrylate 10 10 10 25 25 25 25 50 50 50
polymer, ppm
H2SiFo, ppt1.25 1.251.25 1.25 1.25 1.25 1.25 1.25 1.25 1.25
Free F- 690 690 690 <25<25 680 680 670 670 670
activity, ppm
Abbreviation for Table 3
Slt. = See later table(s).
The citrate concentrations in the working phosphating compositions and the resulting
coating weights and crystal sizes are sho~,-vn in Tables 4 - 11.
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Table 4: RESULTS WITH 10 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES
Comp. Citrate Conc. Coating Weights,C~ystal Size, Other
# g/m2 ~ Observa-
tions
Top Bottom
0.10 1.10 2.62 8- 10 SRD
0.20 1.17 2.83 5 - 8 SRD
2 0.30 0.70 2.90 5 - 8 SRD
3 0.30 1.57 2.67 5 - 8 SRD
3 0.40 0.96 2.68 5 - 8 SRD
3 0.50 0.99 2.86 3 - 5 SRD
3 0.65 1.30 2.87 3 - 5 SRD
3 0.80 1.38 2.71 3 - 5 DVSR
3 1.00 1.04 2.52 3 D
Additional Abbreviations for Table 4
(See notes for previous tables and main text for others)
Comp. # = Composition Number (from Table 3); Conc. = Concentration, g/m2 = grams per
sq~are meter; ~1 = micrometres; SRD = Surface rust and dusting observable after phosphating;
DVSR = Dusting and very slight surface rust observable after phosphating; D = Dusting but no
rust observable after pho~h~tin~.
16
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Table 5: ~ESULTS WITH 10 PPM OF ACRYLATE POLYMER ON lEG SUBSTl~ATES
Comp.Citrate Coating Weight, g/m2 Crystal Size, ~ Other
# Conc. OSS OGS OSS OGS Obser-
Top Bottom Top Bottom
0.10 1.12 3.01 2.88 2.82 5 - 10 - 10 D
0.20 0.88 2.80 2.83 2.97 5- 10 ~ 8 D
2 0.30 0 70 3.07 2.97 2.76 5 - 10 5 - 10 D
3 0.30 1.59 2.43 2.14 2.78 5- 10 5- 10 D
3 0.40 1.14 2.66 2.80 2.83 5 - 10 N.m. D
3 0.50 1.22 2.40 3.06 2.68 8 5 - 10 D
3 0.65 1.27 2.37 2.65 2.72 6 S D
3 0.80 1.14 2.10 2.72 2.71 5 5 D
3 1.00 1.00 2.07 2.11 2.44 5 3 D
Additional Abbreviations for Table 5 (See notes for previous tables and main text for others)
OSS = On steel side; OGS = On galvanized side; N.m. = Not measured.
Table 6: RESULTS WITH 10 PPM OF ACRYLATE POLYMER ON OTHER SUBSTRATES
On HDG Substrate On 2EG Substrate On ~I Substrate
Coat. Wt., g/m2 Crystal Coat. Wt., g/m2 C~ystal Coat. Wt., g/m2 Crystal
Size ~1 Size, ~1 Size,
Top Bottom ~r- Top Bottom Top Bottom
2.96 2.84 10 3.08 2.52 5 2.13 4.10 15 - 20
Additional Abbreviation for Table 6 (See notes for previous tables and main text for others)
Coat. Wt. = Coating Weight
General Note for Table 6
The phosphating composition used for all results in this table was Number 3 from Table 3 with
1.00 ppt of citrate. No surface rust or dusting of the coating was observed.
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Table 7: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES
Comp. Citrate Conc. CoatingWeights,C~ystal Size, Other
m2 ~ O~5~
tions
Top Bottom
4 0.00* 0.61*2.08* 15 - 20* SRD*
4 0.10 0.93 3.76 15 - 20 SRD
4 0.20 1.22 3.62 10- 15 SRD
4 0.30 1.04 3.15 8- 10 SRD
0.30 1.30 2.85 5- 10 SRD
0.40 1.35 2.82 5- 10 SRD
0.50 1.24 2.99 5- 10 DVSR
6 0.50 1.09 3.35 3 - 6 D
7 0.50 0.342.1 ~0.7 3 - 6 DVSR
Footnote for Table 7
*Comparison example, not according to the invention.
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Table 8: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON lEG SUBSTRATES
Comp. #Citrate CoatingWeight, glm2 C~ystal Other
Conc. Size, ~, Obser-
OSS OGS OGS vations
Top Bottom Top Bottom
4 0.00* 0.66* 2.24* 2.51* 3.28*10- 15* SRD*
4 0.10 1.09 4.47 2.73 3.148- 10 D
4 0.20 1.04 4.73 3.29 3.108- 10 D
4 0.30 0.91 4.06 3.29 3.155 - 8 D
0.30 1.36 3.18 2.76 2.905 - 8 D
0.40 1.34 3.19 2.85 2.965 - 8 D
0.50 1.52 3.18 2.78 3.045 - 8 D
6 0.50 0.83 5.08 2.38 3.95 5 D
7 0.50 0.69 2.98 3.71 3.77 5 D
Footnote for Table 8
*Comparison exarnple, not according to the invention.
Table 9: RESULTS WITH 25 PPM OF ACRYLATE POLYMER ON OTHER SUBSTRATES
Comp. #Citrate On HDG On 2EG On ZI
Conc. Substrate SubstrateSubstrate
Coat. Wt., g/m2 Coat. Wt., g/m2 Coat. Wt., glm2
Top Bottom Top Bottom Top Bottom
4 0.30 1.68 3.04 3.13 2.930.41 3.49
7 0.50 3.38 2.81 3.25 3.270.64 4.66
General Note for Table 9
Surface dusting but no rust after phosphating was observed for both exarnples in this table.
19
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Table 10: RESULTS WITH 50 PPM OF ACRYLATE POLYMER ON CRS SUBSTRATES
Comp. Citrate Conc. Coating Weights, Clystal Size, Other
# g/m2 ~u Observa-
tions
TopBottom
8 0.10 1.061.87 8- 10 DVSR
9 0.10 0.582.81 8- 10 SRD
0.15 1.054.80 8- 10 SRD
9 0.20 0.933.64 8- 10 SRD
Table 11: RESULTS WITH 50 PPM OF ACRYLATE POLYMER ON lEG SUBSTRATES
Comp. Citrate Coating Weight, g/m2 Clystal Size, ~ Other
# Conc. OSS OGS OSS OGS Obser-
Top Boffom Top Bottom
8 0.10 0.48 2.62 3.11 4.2110 15 D
9 0. 1 0 1 .04 4.7 1 4.02 4.208 -1 0 1 5 D
0.15 0.91 3.02 3.84 4.278- 10 10 D
9 0.20 0.69 3.75 3.79 3.84 8 5 D
