Note: Descriptions are shown in the official language in which they were submitted.
21~548~1
1 --
Acid aqueous phosphatic solution and process using same for phosphating
- metal surfaces
FIELD OF ~ lNV~llON
The present invention relates to an acid aqueous phosphatic solution and
a phosphating process using same to obtain a phosphatic film covering
metal surfaces, said film providing excellent corrosion protection and
adhesion toward coatings, in particular the coatings obtained by
electrocoating. Surprisingly, the phosphating process carried out at low
temperatures on metal surfaces based on iron, zinc, aluminium, and steel,
is capable of preventing white spots formation, a phenomenon constituting
a problem deeply felt especially by the automobile industry.
PRIOR ART
Since 1917, films obtained from phosphatic aqueous solutions have been
used to prevent corrosion, prolong the short life of metal surfaces, and
improve the paint coating adhesion: the metal surface reacts with the
solution to form a phosphate layer, which is either amorphous or
crystalline depending on the operating conditions.
Some phosphatic solutions have found extensive application and gained
great commercial importance. Said solutions generally contain phosphate
ions, zinc and/or manganese and a component, if any, selected among
nickel, cobalt, copper, magnesium, calcium, nitrite, nitrate, chlorate
and fluoride.
Although, at present, the quality levels of phosphatic solutions are
satisfactory, improv~ ~nts are continuously d~ ~n~ed, in particular by
the motorcar industry, owing to the new requirements set by the
development of the metal substrates used.
Furthermore, the average life of motor vehicles is now slightly longer
21554~ll
f - 2 -
- than 10 years, whereas no treatment capable of preserving bodies from
corrosion and allowing said life to be as long as 10 years has been
developed so far.
The metal supports used at present are based on iron, aluminium, zinc,
and preferably zinc plated steels (galvanized or electroplated) which,
after paint application, proved to be the most resistant to corrosion.
The zinc layer efficiency in preventing corrosion ph~n~ ~nA as well as
its good adhesiveness result from zinc being reactive with C02 and
atmospheric oxygen, which causes the formation of zinc hydro~ycarbonate
10 that quickly adheres to the metal surface and inhibits further corrosion
phPnl ?nA. Zinc also provides cathodic protection to steel, acting as the
anode and undergoing corrosion instead of steel.
As concerns low-zinc-content solutions, the phosphating me~hAn;! Y seem
to be the following:
15 on steel
2 Zn2+ + Fe2+ + 2 pO43 > Zn2Fe(po4)2 4 H20 (phosphophyllite)
on zinc
3 2 P04 > Zn3(P04)2 4 H20 (hopeite)
In the case of solutions ContA; n; ng other metal MeII ions in addition to
20 zinc, such as manganese ions, magnesium ions etc., the phosphatic layer
seems to consist of:
ZnxMeIIy(PO4)2 4 H20
pseudo-phosphophyllite, when x = 1 and y = 2;
pseudo-hopeite, when x = 2 and y = 1.
25 CrystAll;n~ phosphating processes are always conducted in the presence of
an accelerator, i.e. an oxidizer, generally inorganic and sometimes
organic, meant for obtaining surface conversion in a shorter and
2 1 ~ 3 4 8 4
- 3 -
industrially acceptable time. The accelerator action is twofold: it
~ depolarizes the metal surface by acting in particular in the high
electronic density (microcathodic) areas, and at the same time oxidizes
the metals dissolved in the microanodic attack area causing their
precipitation as insoluble phosphatic salts.
Various accelerators, i.e. oxidizers, reducers, or mixtures thereof, are
used at the present state of the art.
The nitrite (preferably as a sodium salt) is - among external cl ~on~nts
- the most widely used accelerator in microcrystalline phosphating
processes.
The success of nitrite reasonably results from its easy avAil~h;lity, low
cost and high oXi~i~ing power. However, the use of nitrite and/or nitro
derivatives meets with insurmountable ecological problems, which cannot
be dealt with successfully in compliance with the regulations in force.
In fact, this compound has major drawbacks from the technical and
ecological points of view, being thermally unstable under the usual
operating conditions. Said instability inevitably brings about the
formation of nitrogen oxide, whose vapours - having general formula NOx -
vented to the atmosphere are highly polluting and aggressive.
Furthermore, in the processing baths, nitrite tends to be converted to
nitrate ions, which require a troublesome treatment in purification
plants. The aforesaid problems as well as the serious hazard connected
with nitrite industrial handling and storage (a toxic and comburent
substance according to EC standards in force) involve high operating
costs, with no certainty of operating in compliance with the regulations
in force.
In view of the aforementioned problems, there is an urgent need for
215a48~
_
finding an alternative accelerator free from nitro derivatives and
~ capable of providing technological performances that may at least
approximate to those of the traditional processes based on nitrite.
That is why the attention has been turned again to hydroxylamine, an
ecologically safe product, which has been used as accelerator of
phosphating processes since the early '50s.
However, the procedures using hydroxylamine cannot be used for
phosphating zinc plated steels and surfaces based on aluminium and iron,
because of the formation of white spots, i.e. punctiform white
efflorescences of variable size (average diameter: 50 to 150 ~m; average
height: 100 to 400 um), which are spread at random on the phosphated zinc
plated surface after the phosphating stage (D. Saatweber, Galvanized
Sheet and Cationic ED Primer: Synergism for Fini.ching Optimization, ATA
27th Feb., 1989, Milan, Italy, Surface Fini~hing and Corrosion Protection
in Aut -biles). The successive cathode-type electrocoating does not
correct said defects, but replicates extrudates and layer exactly:
therefore, the finish~d product is absolutely unacceptable.
The chemical nature of said ph~nf - on, also known as "white specking" or
"nubbing", has not been fully clarified yet; however, its origin seems
electrochemical. In fact, it was found that the cathodic polarization of
zinc plated surfaces can prevent white spots formation (W. Rausch,
Industrie Lackerbetrieb, 1981, 12,413).
When fed to the phosphating bath, the metal surfaces to be treated, in
particular the surfaces based on zinc, usually exhibit non-uniform
residual oxidation areas. It follows that preferential polarities arise
in the course of the phosphating process, which always includes a
preli nAry pickling stage, wherein the phosphoric acid generated by the
2I~54~4
phosphatic system produces superficial etching. Anodic corrosion develops
~ locally in the acid medium, with formation of punctiform cavities
characterized by a vacancy of surface layer zinc. In the surface areas
where iron is exposed, a "galvanic cell" probably operates on iron and
metal zinc, thus allowing zinc dissolution to continue. Consequently,
zinc hydroxides and phosphates might precipitate in excessive amounts and
accumulate at the cavity limits. Phosphated surfaces would thus exhibit
small blfl~ki Sh cavities characterized by lateral whitish deposits, mainly
consisting of zinc hydroxides and phosphates, which would form the
typical swollen efflorescence (Guy Lorin, La phosphatation des metaux,
20-21, Edition Eyrolles, 1973).
As already mentioned, this phPnl- on is particularly pronounced when
hydroxylamine is used as phosphating accelerator.
According to the prior art, the only remedy for removing the white spots
15- that form after the phosphating process is of mechanical type, e.g.
sanding or rubbing with paper or cloth. Such a hand-performed operation
clearly involves too high costs of labour to be commercially viable.
Different solutions of the problem connected with white spots formation
have been proposed in specific cases.
By way of example, European patent EP 228,151 discloses a phosphating
bath cont~ining zinc, P04 ion, manganese, and fluoride ions, and provides
for the use of various accelerators, such as nitrite and nitro
derivatives, but not hydroxylamine. According to the inventors, the
problem of white spots formation may be partially solved by re~lcing the
concentration of chloride ions in the phosphatic solution and, obviously,
also of chlorate ions which, by reduction, slowly give chlorides.
British patent application GB 2,179,680 identifies the presence of
2155~84
chloride ions as one of the major causes for white spots formation and
~ provides for a phosphating solution that can be applied to zinc plated
metal surfaces as a film capable of reducing said ph~nr ~non. This result
would be attained - though not to a wholly satisfatory extent - by
nullifying the effect of chlorides through proportional additions of
fluorides. In fact, the aforesaid solution shollld contain fluorides at a
F /Cl ratio at least of 8:1 by weight. Furthermore, the chloride ions
concentration should be of 50 ppm max., preferably of 20 ppm max., and
optionally pretreatments of the metal surface should be carried out with
solutions having a chlorides content of 100 ppm max. Said limits may be
hardly proposed to the industry: in fact, values of 20 or 50 ppm are
often exceeded even only by the main water salinity and may be easily
reached also in phosphating baths prepared with d~ in~ralized water,
owing to the drag out of main water used for previous wa.ching.c.
European patent EP 0264151 looks for the solution of ~he problem of white
spots in a metal surface pretreatment stage and provides for a rinse
operation - prior to activation - with a solution contAin;ng a mixture of
sodium silicates, borates and nitrites.
European patent EP 0224190 discloses the use of an activating solution
based on titanium phosphates, added with disodium tetraborate or other
~lk~l ine borates at a P04/B407 ratio of 1 min. Addition of B407 reduces
the formation of white spots, which thus occurs at widely separated
intervals, but does not wholly el;minate the phen- on. Moreover, as
disclosed in said patent, a serious pollution problem is brought about by
the high amounts of Na2B407.10 H20 required (4 to 8 g/l).
None of the aforementioned patents provides for the use of hydroxylamine
as accelerator.
215~4
It is clear that the problem of white spots has not been solved so far:
~ in particular, the problem hardly admits solution if hydroxylamine is
used as accelerator, which makes the problem particularly serious.
~Ub~TARY
It has surprisingly been found that an acid aqueous solution contAining
hydroxylamine phosphate in association with a cationic surfactant, in
particular a quaternary ammonic surfactant, allows the obtAi -nt, within
a time meeting industrial requirements, of phosphatic layers having good
corrosion resistance and adhesion to a paint coating, without formation
of white spots.
It is a further object of the present invention a process, based either
on spraying or on immersion, for phosphating metal surfaces with said
solution, at a temperature of 40C to 55C, for a period of 1 to 5
minutes.
DT~r~n.Tm DESCRIPTION OF THE lNV~.llON
The following detailed description sets forth characteristics and
advantages of the phosphating solution and of the process using same
according to the present invention.
The present invention relates to an acid aqueous phosphating solution
containing hydroxylamine phosphate and a cationic surfactant, preferably
a quaternary ammonic surfactant, at given concentrations and ratios. More
precisely, the present invention relates to phosphating solutions
contAin;ng 0.6 to 3.0 g/l hydroxylamine phosphate and 0.001 to 1 g/l of
cationic surfactant, preferably 0.005 to 0.1 g/l. The hydroxylamine
phosphate/cationic surfactant ratio may range from 0.6 to 1000 by weight,
preferably from 10 to 200.
The solution may also contain 0.003 to 0.08 g/l of copper ions; 0.05 to
8 '1
-- 8 --
0.3 g/l of at least a polyfunctional sequestering agent selected from the
group consisting of aminated polyacid complexing agents acting as
accelerators, such as EDTA, and organic polyacids, such as tartaric and
citric acids, and preferably EDTA and/or tartaric acid at a concentration
of 0,08 to 0,1 g/l; an amount of non-ionic emulsifier, acting as
defoaming agent, compatible with the phosphating process and the usual
passivation and electrocoating treatments, ranging from 10 to 30% by
weight of the cationic surfactant content.
The phosphating compositions according to the present invention
conveniently contain:
- 5 to 25 g/l phosphate ions;
- 0.5 to 2.0 g/l zinc ions, preferably 0.5 to 1.5 g/l;
- 1.5 to 4.0 g/l nitrate ions;
- 0.3 to 1.2 g/l ~ng~nPse ions;
- 0.001 to 0.1 g/l iron ions;
- 0.4 to 1.1 g/l nickel ions;
- 0.3 to 1.2 g/l total fluoride ions, deriving from hydrofluoric acid,
fluorosilicilic acid or other suitable sources;
- o.6 to 3.0 g/l hydroxylamine phosphate; and
- 0.001 to 1 g/l cationic surfactant, preferably 0.005 to 0.1 g/l.
In the phosphating composition of the invention, said amount of nickel
ions may be substituted by a combination of magnesium and cobalt ions,
wherein magnesium ions range from 0.5 to 1.5 g/l and cobalt ions range
from 0.05 to 0.2 g/l.
Since, as previously mentioned, the nature of white spots has not been
clarified yet, also the action produced by the hydroxylamine
phosphate/cationic surfactant system can be hardly understood.
~ 1 5 5 L~ 8 ~
This is even more surprising because it is only hydroxylamine phosphate,
~ and not other hydroxylamine salts, that produces the result intended.
Any chemical me~hAn; acting through hydroxylamine phosphate and not,
e.g., the corresponding sulphate, can be hardly hypothesized.
It is also surprising that, among the various surfactants tested, the
anionic surfactants tend to increase white SDots formation, whereas non-
ionic surfactants do not affect the occurrence of said phenomenon.
Particularly suitable cationic surfactants are the ammonic ones selected
from the groups consisting of:
- cocodibenzylr ~nium chloride, having an alkylic chain consisting of 12
to 14 carbon atoms;
- polyethoxylated and polypropoxylates of alkyl~ ~nium chloride and
phosphate;
- benzalkonium chloride and derivatives thereof, having a side chain
consisting of 12 to 14 carbon atoms;
- N-alkyl~ ium chloride, with an alkyl residue consisting of 12 to 18
carbon atoms. the .~ ining residues consisting of H and/or methyl;
- alkyl polyglycolethers of ammonium chloride and sulphate of formula
(I)
IRl
R-0-(CH2CH2~0)n-(cH2)m I R3 Cl or 1/2 S04 (I)
R2
where n = 4 to 18, m = 1 or 2, R1, R2, R3 = H and/or methyl, with R being
a linear or branched alkyl cont~ining from 10 to Z2 carbon atoms.
Particularly preferred are the compounds of formula (I), where n ranges
from 10 to 12, m is 1 or 2, R1, R2, R3 = H and/or methyl, with R being
C12-C14 alkyl, which prove to be highly effective for white spots
215~ 18~
-- 10 --
removal.
~ The cationic surfactants may suitably form even in situ in the
phosphating solution, by adding to the phosphating bath a surfactant of
formula:
ICH3
(CH2CH2-0)n~H (CHCH2-0)n~H
R-N and/or R-N
(CH2CH2-0)n~H (ICHCH2-0)n~H
CH3
wherein R and n have the above meaning.
Although the connection of white spots formation with the presence of
chlorides has not been demonstrated, evidences have been provided that
white spots are completely removed in the presence of a cationic
surfactant at a surfactant/chlorides ratio of 1:3 by weight.
It has also been found that the copper ion contained in the rl ~i sd
solution contributes to the imp~-ov t in quality of the phosphatic
layer, which becomes more conductive. Said advantageous use of copper
ions is made possible by the presence of the hydroxylamine
phosphate/cationic surfactant system which, in any case, hinders the
formation of white spots. In the absence of said system, copper ions
cause white spots formation already at concentrations of 0.003 to 0.005
g/l.
The phosphatic solution according to the present invention exhibits a
total acidity value ranging from 10 to 28 points, a free acidity value
ranging from 0.5 to 2.0 points, at an acid ratio (i.e. total acidity/free
acidity ratio) of 5 to 56. With said acidity values, phosphatic films may
be obtained at a low cost and the metal surface does not undergo
~1~5~8~1
pronounced corrosion.
In the present description, the total acidity value refers to the number
of illilitres of 0.1 N NaOH necessary to titrate 10 ml of the cl~
phosphatic solution using phenolphthalein as indicator and the free
acidity value refers to the number of illilitres of 0.1 N NaOH necessary
to titrate 10 ml of the cl~i -d phosphatic solution using methyl yellow
as indicator.
The phosphating process according to the present invention may be
conducted by spraying or immersion or a combination thereof, for a
period of 1 to 5 min., at a temperature of 40C to 55C. At temperatures
below said range, acceptable layers could be obtained only after long
processing times, whereas at temperatures above said range, the
phosphating accelerator would decompose more quickly, which would
unbalance the solution components concentrations and make it difficult to
obtain satisfactory phosphatic films.
The microcrystalline phosphate layer obtained on the basis of the
procedure of the present invention weighs 1.5 to 5.0 g/m2.
The claimed process, carried out either by spraying or by immersion,
reduces white spots formation of 98%.
The phosphatic film can be satisfactorily applied also to complex-shaped
articles, such as automobile bodies.
The phosphating process based on immersion according to the present
invention is carried out at a temperature preferably ranging from 45C to
50C, for a period of 2 to 5 min.
The acid aqueous phosphatic solution used in said treatment preferably
contains 13 to 15 g/l phosphate ions, 1.0 to 1.5 g/l zinc ions, 2.5 to
3.5 nitrate ions, 0.6 to 1.1 g/l manganese ions, 0.001 to 0.05 g/l iron
2155~4
- 12 -
ions, 0.4 to 0.6 g/l nickel ions, 0.6 to 0.8 g/l fluoride ions, 1 to 2
~ g/l hydroxylamine phosphate and 0.01 to 0.1 g/l cationic surfactant. The
solution may also contain 0.003 to 0.006 g/l copper ions and 0.05 to 0.3
g/l organic polyfunctional sequestering agent, preferably EDTA and/or
tartaric acid.
The total acidity value preferably ranges from 18 to 22 points and the
free acidity value from 1 to 2 points.
Said procedure by immersion yields microcryst~lline phosphatic layers
weighing 1.5 to 3.5 g/m2 on iron substrates, and 2 to 5 g/m2 on zinc
plated sheets.
The phosphating process based on spraying according to the present
invention is carried out at a temperature preferably ranging from 45C to
50C, for a period of 1 to 3 min., under a spraying-pressure of 1 to 2.5
atm.
The acid aqueous phosph~tic solution used in said treatment preferably
contains 9.0 to 11.2 g/l phosphate ions, 0.8 to 1.2 g/l zinc ions, 1.7 to
3.0 nitrate ions, 0.4 to 0.7 g/l manganese ions, 0.001 to 0.04 g/l iron
ions, 0.4 to 0.5 g/l nickel ions, 0.4 to 0.7 g/l fluoride ions, 0.8 to
1.6 g/l hydroxylamine phosphate and 0.01 to 0.1 g/l cationic surfactant.
The solution may also contain 0.003 to o.oo6 g/l copper ions and 0.05 to
0.3 g/l organic polyfunctional sequestering agent, preferably EDTA and/or
tartaric acid.
The total acidity value preferably ranges from 13 to 14 points and the
free acidity value from 0.6 to 0.8 points.
Said procedure by spraying yields microcryst~lli n~ phosphatic layers
weighing 1 to 3.5 g/m2 on iron substrates, and 1.5 to 3.5 g/m2 on sheet
iron zinc plated electrolytically.
2I55~8~
- 13 -
According to the procedure of the present invention, immersion and
immersion/spraying treatments are preferred to spraying and
spraying/immersion treatments.
Finally, a treatment combining spraying with immersion may consist of
immersion at 45C to 50C, for a period of 100 to 200 sec., followed by
spraying at 45C to 50C, for a period of 20 to 50 sec., or of spraying
at 45C to 50C, for a period of 20 to 50 sec., followed by immersion at
45C to 50C, for a period of 100 to 200 sec. The treatment based on
immersion followed by spraying is particularly suitable for complex-
shaped articles, such as automobile bodies.
The constituents of the acid aqueous phosphatic solution of the present
invention may be obtained from the following compounds:
- hydroxylamine phosphate is a stable salt of formula (NH20H)3.H3P04 or
(NH30H)3.P04. It is to be stressed once again that a hydroxylamine salt
other than phosphate cannot be used in the phosphating solutions of the
invention. In particular, it would be profitable from an industrial point
of view to use hydroxylamine sulphate, a low-cost and easily-available
stable salt; however, said use proved to be impossible because sulphate
ions in amounts higher than 500 ppm, favour white spots formation, i.e.
they act as chloride ions.
- The source of phosphate ions may be phosphoric anhydride, phosphoric
acid, zinc phosphate, zinc monohydrogen phosphate, zinc dihydrogen
phosphate, manganese phosphate, manganese monohydrogen phosphate,
manganese dihydrogen phosphate, etc., and preferably phosphoric acid.
- The source of zinc ions may be zinc oxide, zinc carbonate, etc., and
preferably zinc oxide.
- The source of manganese ions may be manganese carbonate, manganese
2155~8fl
oxide, the aforementioned manganese phosphates, etc., and preferably
manganese carbonate.
- The source of iron ions is preferably ferric nitrate; nevertheless, at
the initial step of preparation of the phosphating bath, it is possible
even not to add iron to said bath, since iron ions can form spontaneously
during the phosphating of iron-based surfaces, due to the acid attack of
the same surfaces.
- The source of nickel ions may be nickel nitrate, nickel carbonate,
nickel phosphate, etc., and preferably nickel nitrate.
~ The source of fluoride ions may be fluosilicilic acid, hydrofluoric
acid, fluoboric acid, and metal salts thereof, and preferably
fluosilicilic acid.
- The copper ions are preferably added to the solution as copper nitrate.
Finally, with a view to obt~ining the aforesaid acidity values, the
solutions may be modified or added with alkaline metal hydroxides,
ammonium hydroxide, and preferably sodium hydroxide.
The metal surfaces to be treated according to the present invention
include surfaces based on iron, zinc, aluminium and/or their respective
alloys. Said metal surfaces may be treated either singly or in
combination.
The new process is particularly advantageous for articles consisting of
zinc- and iron-based surfaces, as is the case of automobile bodies.
Examples of zinc-based surfaces are zinc plated sheet steel, ski ~d
sheet steel, sheet steel zinc plated by electrodeposition, sheet steel
zinc-alloy plated by electrodeposition, and complex sheet steel zinc
plated by electrodeposition.
The acid aqueous phosphatic solutions of the present invention may be
215S~8~
-
conveniently prepared by diluting an aqueous concentrate contA;n;ng the
solution constituents at the right ratios by weight and adding some
elements, as required, e.g. pH adjusting agents or accelerators.
m e process of the invention includes advantageous pretreatments of the
metal surfaces, i.e. degreasing with weakly or strongly alkaline
degreasers or with acid degreasers, followed and/or preceded by one rinse
with water. The metal surfaces may be then subjected to conditioning with
a titanium or zirconium solution. Particularly suitable for the purpose
is a solution containing 0.0003% to 0.05%, preferably 0.0005% to 0.001%,
titanium on phosphatic support.
Furthermore, once phosphating has been carried out according to the
invention, the phosphated surfaces - especially if a coating of same is
envisaged - undergo advantageous posttreatments, such as a rinse with a
dilute chromic solution contA;n;ng, e.g., 0.025% to 0.1% chromium in the
form of chromium (III) or chromium (VI) or a mixture thereof.
Alternatively, it is possible to perform rinses with aqueous solutions
contA;n;ng poly-4-vinyl phenols or condensates thereof with an aldehyde
or a ketone.
It is also possible to perform passivation treatments with metal salts,
such as aluminium, zirconium, etc.
Once the aforesaid final rinses have been made, the surfaces exhibit a
good resistance to corrosion and a good adhesion to the paint layer later
applied by cathode-type electrocoating, since no white spots formation
occurred.
The following examples are reported by way of indication, not of
limitation of the present invention.
2155~8~
- 16 -
- EXaMPLE 1
Influence of Anionic, cationic and non-ionic surfactants on white spots
formation
Materials and Methods
Tests were conducted on steely sheets, zinc plated on both sides (with an
8 to 10 ,um thick zinc layer) by electrodeposition, i.e. by electrolytic
zinc plating. The said sheets were treated according to the following
operating cycle:
DEGREASING STAGE
The degreasing solution used consisted of:
Disodium phosphate ca. 7 g/l
Sodium metasilicate.5 H20 ca. 7 g/l
Trisodium phosphate.12 H20 ca. 3 g/l
Neutral sodium pyrophosphate ca. 1.8 g/l
15 Non-ionic surfactants ca. 1 g/l
Hydrotropes ca. 1 g/l
The treatment was carried out by immersion at a temperature of 55C to
60C, for a period of 3 to 5 minutes.
ACTIVATION STAGE
The activating solution used consisted of:
Titanium 5 to 6 mg/l
P04 150 to 200 mg/l
P301o 450 to 500 mg/l
The treatment was carried out by immersion at a temperature of 20C, for
a period of 1 minute.
PHOSPHATING STAGE
Phosphating was carried out by immersion at a temperature of 50C, for a
- 215548~
- 17 -
- period of 3 minutes, using standard 5 1 vessels constructed of antiacid
material, heated electrically to the desired temperature, and maintained
under magnetic stirring.
The three different phosphating solutions used consisted of:
P04 ions ca. 13 to 15 g/l
Zinc ions ca. 1 to 1.2 g/l
N03 ions ca. 3 to 3.5 g/l
Manganese ions ca. 1 to 1.2 g/l
Nickel ions ca. 0.4 to 0.5 g/l
Iron ions ca. 0.005 to 0.02 g/l
Total fluoride ions ca. 660 to 715 mg/l
Total acidity value 18 points
Free acidity value 1.8 points
The aforesaid solutions were added with hydroxylamine phosphate (2 g/l),
chloride ions (lOC ppm, 0.1 g/l), and a surfactant at a concentration of
0.1 g/l:
- BATH 1 was also fed with a non-ionic emulsifier consisting of ethylene
oxide-propylene oxide block copolymer;
- BATH 2 was also added with a cationic surfactant falling within the
scope of this invention, in particular alkyl polyglycolether of ammonium
chloride of formula (I), where R = C12, n = 11 and m = 1;
- BATH 3 was also added with an anionic surfactant, in particular sodium
dodecylbenzeneslll phonflte .
Once the sheets had undergone the aforesaid operating cycle, they were
anaIyzed-
White spots may be seen with the naked eye, but preferably through an
optical microscope, being 0.5-1.5 mm microdome-shaped punctiform white
215S484
- 18 -
- efflorescences, which show up on the grey surface of a phosphated sheet
zinc plated by electrodeposition.
Results
Phosphating BATH White spots (WS)
1 present on sheets
2 absent on sheets
3 massively present on sheets
The results of said test prove that non-ionic surfactants do not hinder
white spots formation, anionic surfactants favour it, and the cationic
surfactants of the invention inhibit it.
EXAMPLE 2
D~to n~tion of the ratio of c~tionic surfactant of the invention to
chloride ions suitable for preventing white spots formation
Materials and Methods
Tests were conducted on steely sheets (FeP04), zinc plated on both sides
(with an 8 to 10 ,um thick zinc layer) by electrodeposition, i.e. by
electrolytic zinc plating. Degreasing and activating stages were as
described in Example 1.
Phosphating was carried out by immersion at a temperature of 50C, for a
period of 3 minutes, using standard 5 l vessels constructed of antiacid
material, heated electrically to the desired temperature, and maintained
under magnetic stirring.
A phosphating bath as per Example 1 was added with hydroxylamine
phosphate (2 g/l) and chloride ions (100 ppm; 0.1 g/l). The bath was
repeatedly added with alkyl polyglycolether of ammonium chloride of
formula (I), where R = C12, n = 11 and m = 1, to obtain the cationic
2 1 r) 5 4 8 4
-- 19 --
- surfactant concentration required for white spots total eli in~tion, even
in the presence of chloride ions, which seem to ~xi i7e white spots
formation.
Results
Surfactant White spots (WS)
0 ppm present
5 ppm present
10 ppm present
15 ppm present
20 ppm present
30 ppm absent
The results of said test prove that a cationic surfactant of the
invention/chloride ions ratio of 1:3 is enough to prevent white spots
formation.
EXAMPLE 3
De~e. n~tion of the max. amount of cationic surfactant of the invention
usable in iron phosrh~ting process
Materials and methods
Two types of ferrous plates were analyzed:
TYPE 1 - Cold-rolled plate, FeP04 type, according to UNI standard 5961-67
(April 1967), of common use in motor vehicle manufacture;
TYPE 2 - 0.8 mm thick cold-rolled ferrous plate, type R, available from
Q-Panel (U.K.), according to standard 750.
Said plates were treated according to the degreasing and activating
stages described in Example 1. Phosphating was carried out by immersion
at a temperature of 50C, for a period of 3 minutes, using standard 5 1
Z1~5~4
- 20 -
- vessels constructed of antiacid material, heated electrically to the
desired temperature, and maintained under magnetic stirring.
The phosphating solution used consisted of:
P04 ions ca. 13 to 15 g/l
Zinc ions ca. 1 to 1.2 g/l
N03 ions ca. 3 to 3.5 g/l
Manganese ions ca. 1 to 1.2 g/l
Nickel ions ca. 0.4 to 0.5 g/l
Iron ions ca. 0.005 to 0.02 g/l
Total fluoride ionsca. 660 to 715 mg/l
Total acidity value 18 points
Free acidity value 1.5 points
The aforesaid solution was added with hydroxylamine phosphate (2 g/l),
chloride ions (150 ppm; 0.15 g/l) and with increasing amounts of alkyl
polyglycolether of ammonium chloride of formula (I), where R = C12, n =
11 and m = 1; after each addition of the cationic surfactant, the sheets,
after pretreatments, were phosphated according to the aforementioned
procedure. The nature of the phosphated layer obtained was ~x, ne~.
Results
SurfactantQuality of the phosphatic layer
(mg/l) TYPE 1 TYPE 2
0 good good
300 good good
500 good good
700 good good
1000 good good
2155 18 l
- 21 -
- Said results prove that the cationic surfactants according to the present
invention do not affect iron phosphating; therefore, there is no limit to
their concentration in the phosphating bath up to 1000 ppm (1 g/l).
EXAMPLE 4
Influence of the cationic surfactant of the invention on the ~ho~h~l;ne
of sheet iron and zinc plated sheets
Materials and methods
Tests were conducted on ferrous sheets zinc plated on both sides by
electrodeposition, i.e. by electrolytic zinc plating.
Once degreased and activated as described in Example 1, the sheets were
phosphated in the presence and in the absence of the cationic surfactant
of the invention of formula (I), where R = C12, n = 11 and m = 1.
Phosphating was carried out by immersion at a temperature of 50C, for a
period of 3 minutes, using standard 5 l vessels constructed of antiacid
material, heated electrically to the desired temperature, and maintained
under magnetic stirring.
The phosphating solution used consisted of:
P04 ions ca. 13 to 15 g/l
Zinc ions - ca. 1 to 1.2 g/l
N03 ions ca. 3 to 3.5 g/l
Manganese ions ca. 1 to 1.2 g/l
Nickel ions ca. 0.4 to 0.5 g/l
Iron ions ca. 0.005 to 0.02 g/l
Total fluoride ions ca. 660 to 715 mg/l
25 Hydroxylamine phosphate ca. 2 g/l
Total acidity value 18 points
Free acidity value 1.5 points
215548ll
- 22 -
- The aforesaid solution was added with the following amounts of chloride
ions: 50 ppm (solution A), 100 ppm (solution B) and 150 ppm (solution C).
For purpose of comparison, solutions contAining the aforesaid amounts of
chloride and increasing amounts of the cationic surfactant of the
invention, i. e. 30 ppm (solution A'), 60 ppm (solution B') and 90 ppm
(solution C'), were prepared. Solutions A', B', and C' were also added
with a defoaming agent.
Once the aforesaid sheets had undergone the described operating cycle,
the presence of white spots was inspected with the naked eye.
1 o ReSults
Solution [Cl ] Surfactant conc.WS observed
A 50 ppm absent some
A' 50 ppm 30 ppm none
B 100 ppm absent many
B' 100 ppm 60 ppm none
C 150 ppm absent very many
C' 150 ppm 90 ppm none
Said results prove that the cationic surfactants according to the present
invention efficiently inhibit white spots formation.
EXAMPLE 5
SCAb Corrosion Test and Wet A~he6i nn Test on pho~rhAted plates
accol~ing to the present invention.
Materials and Methods
Tests were conducted on three types of steely sheets:
TYPE 1 - Cold-rolled steely plate, FeP04 type;
TYPE 2 - Zinc steely sheet plated on both sides (with a 7 ,um thick zinc
- - 2~i4~'1
- 23 -
- layer) by electrodeposition, i.e. by electrolytic zinc plating;
TYPE 3 - Hot zinc plated sheet with smooth f;ni~hing (with a 10 to 11 ,um
thick zinc layer).
Said sheets were treated according to the following operating cycle:
DEGREASING STAGE
The degreasing solution used consisted of:
Disodium phosphate ca. 7 g/l
Sodium metasilicate-5 H20 ca. 7 g/l
Trisodium phosphate 12 H20 ca. 3 g/l
10 Neutral sodium pyrophosphate ca. 1.8 g/l
Non-ionic surfactants ca. 1 g/l
Hydrotropes ca. 1 g/l
The treatment was carried out by immersion at a temperature of 50C to
60C, for a period of 2 to 5 minutes.
RINSE STAGE
The rinse was carried out using common water at room temperature.
ACTIVATION STAGE
The activating solution used consisted of:
Titanium 8 to 9 mg/l
P04 130 to 150 mg/l
P207 350 to 400 mg/l
The treatment was carried out by immersion at a temperature of 20C to
40C. for a period of 30 sec. to 120 sec.
PHOSPHATING STAGE
Phosphating stage was carried out, both by spraying treatment (A) and by
immersion/spraying treatment (B).
A) Phosphating by spraying treatment was carried out at a temperature of
21~548~
- 24 -
- about 50C, for a period of 180 sec.
The phosphating solution used consisted of:
Hydl-o~ylamine phosphate 1.3 g/l
cationic surfactant of formula (I) 0.02 g/l
5 P04 ions 21 g/l
Zinc ions 0.6 g/l
N03 ions 3 g/l
Manganese ions 1 g/l
Magnesium ions 1 g/l
10 Cobalt ions 0.1 g/l
Iron ions 0.01 g/l
Total fluoride ions 780 mg/l
Total acidity value 24.5 points
Free acidity value 1.0 points
Said surfactant is the alkyl polyglycolether of ammonium chloride of
formula (I), where R = C12, n = 11 and m = 1;
B) Phosphating by immersion/spraying treatment was carried out at a
temperature of about 50C, for a period of 180 sec., using in the first
immersion phase standard 5 l vessels constructed of antiacid material,
heated electrically to the desired temperature and maintained under
magnetic stirring, followed by spraying for a period of 30 sec.
The phosphating solution used consisted of:
Hydroxylamine phosphate 1.5 g/l
cationic surfactant of formula (I) 0.02 g/l
25 po4 ions 23-5 g/l
Zn 0.7 g/l
N03 ions 3-5 g/l
2155~84
- 25 -
- Manganese ions 1.1 g/l
~a~nesium ions 1.1 g/l
Cobalt ions 0.11 g/l
Iron ions 0.01 g/l
Total fluoride ions 880 mg/l
Total acidity value 27.5 points
Free acidity value 1.3 points
Said surfactant is the alkyl polyglycolether of a_monium chloride of
formula (I), where R = C12, n = 11 and m = 1;
RINSE STAGE
The rinse was carried out using common water at room temperature.
PASSIVATION STAGE
The treatment was carried out by immersion at a temperature of 20 to
40C, for a period of 30 to 120 sec., in a passivating solution
consisting of
H2Cr207 0.15 g/l
Cr(N03)3 0.20 g/l
RINSE STAGE WITH DEMINERALIZED WATER
The rinse was carried out at room temperature, for a period of 10 to 60
sec., by immersion in ~emineralized water.
All the above mentioned sheets underwent the aforesaid operating cycle,
yelding microcryst~lline phosphate layers of even appearance, weiEhing
1.5 to 3.5 g/m2 on iron substrates, and 2 to 4.5 g/m2 on steely sheet
zinc plated by electrodeposition or hot-plated. The layer weights
obtained, calculated according to Standard UNI/ISO 3892, are summarized
hereinbelow:
- 21~5~
- 26 -
PHOSPHATING TREATMENT WEIGHT OF THE PHOSPHATIC LAYERS (g/m2
Type 1 Type 2 Type 3
SPRAYING 2 3.5 3
IMMERSION/SPRAYING 3 4 3
The sheets, after the above mentioned operating cycle, underwent a three-
coats painting according to a typical automobile treatment (cathodic-
epoxidic primer, epoxidic undercoat and alkyd-enamel topcoat), obtAining
a total thickness of 95 to 105 ,um, and were subsequently subjected to
corrosion and adhesion tests, as reported hereinbelow.
Scab Corrosion Test (Outdoor Corrosion)
The coated sheets, painted as above, underwent Scab Corrosion Test
according to FIAT standard 500412 (test method 50493/02), relating to the
resistance of coatings to corrosion, after chipping damage by stones and
other flying objects, and after incisions through the film to the
substrate.
The coated test panels were preliminary submitted to a conditioning
stage, by immersion in demineralized water, at 38C for 120 hours,
followed by protection of the panels edges with adhesive tape or wax. At
least an hour after said pre-treatment, standardized road gravel was
projected by means of a controlled air blast at half part of the coated
specimens in a gravellometer, while on the L-~- 9in;ng half parts of the
specimens an incision was made through the film to the substrate, with an
angle of 45 deg. to the edges of the specimens.
Then the panels were exposed to atmospheric agents, being protected
against the rain, and they were salt sprayed with a solution of NaCl 5%
twice a week.
215~48~
- 27 -
- After an exposure period of 6 months, the sub-film penetration was
measured, reporting the corrosion-removal (mm) along incision on either
side. The results are as follows:
TYPE OF SHEET CORROSION (mm) CORROSION (mm)
after treatment (A)after treatment (B)
Type 1 0-1 0-0.5
Type 2 2 1-1.5
Type 3
As the max. penetration admitted by the above mentioned FIAT standard is
8 mm after an exposure period of 1 month, the above results prove to be
fully satisfactory.
Wet Adhesion Test
After water-immersion of the coated test panels at a temperature of
50+2C, for a period of 120 hours, an area of the panels was cross-cutted
according to a lattice pattern, through the film to the substrate, and
the adhesion was measured following the Tape Test according to ANSI/ASTM
D 3359-76-
Type of sheet Wet Adhesion Wet Adhesion
aftertreatment (A) after treatment (B)
Type 1 5 5
Type 2 5 5
Type 3 5 5
According to the scale of adhesion, 5 indicates that no flaking has
occurred from the surface of cross-cut area and the edges of the cuts are
completely smooth, while O indicates that flaking has occurred from more
than 65% of the cross-cut surface.
21554g'1
- Test of resistance of coatings to chipping damage by stones
The coated sheets, painted as above, underwent a test of chip resistance
of coatings in a gravellometer, according to ASTM D 3170-74.
Type of sheetChipping damageChipping damage
after treatment (A) after treatment (B)
Type 1 7B 7B
Type 2 7B 7B
Type 3 6B 6B
The resultant chipping effects were evaluated by comparison with a set of
reference photographs; lD indicates more than 250 chips on a surface of
more than 6 mm diameter, 3C indicates 100-150 chips on a surface of 3-6
mm diameter, 5B indicates 50-74 chips on a surface of 1-3 mm diameter and
7A indicates 10-24 chips on a surface of less than 1 mm diameter.
EXAMPLE 6
Influence of cAtinnic surfactant of the invention on rhosrh~tic
films and on co~osion resistance
Materials and Methods
Tests were conducted on two types of steely sheets:
TYPE 1 - Cold-rolled steely plate, FeP04 type;
TYPE 2 - Zinc steely sheet plated on both sides (with a 7 ~m thick zinc
layer) by electrodeposition, i.e. by electrolytic zinc plating.
Said panels were treated according to the following operating cycle:
DEGREASING STAGE
The degreasing solution used consisted of:
Disodium phosphate ca. 7 g/l
Sodium metasilicate-5 H20 ca. 7 g/l
Trisodium phosphate-12 H20 ca. 3 g/l
2 ~ g 4
- 29 -
Neutral sodium pyrophosphate ca. 1.8 g/l
Non-ionic surfactants ca. 1 g/l
Hydrotropes ca. 1 g/l
m e treatment was carried out by immersion at a temperature of 50C, for
a period of 3 minutes.
RINSR STAGE
m e rinse was carried out using common water at room temperature, for a
period of 1 minute.
ACTIVATION STAGE
The activating solution used consisted of:
Titanium 8 to 9 mg/l
P04 130 to 150 mg/l
P207 350 to 400 mg/l
m e treatment was carried out by immersion at a temperature of 20C, for
a period of 1 minute.
PHOSPHATING STAGE
Phosphating stage was carried out by immersion at a temperature of 50C,
for a period of 3 minutes, using standard vessels constructed of antiacid
material, heated electrically to the desired temperature, and mantained
under magnetic stirring.
The sheets were phosphated in the absence (Treatment A) and in the
presence of 0.09 g/l of the cationic surfactant of the invention of
formula (I), where R = C12, n = 11 and m = 1 (Treatment B).
m e phosphating solutions used were as follows:
P04 ions ca. 13 to 15 g/l
Zinc ions ca. 1 to 1.2 g/l
N03 ions ca. 3 to 3.5 g/l
215548~
- 30 -
Manganese ions ca. 1 to 1.2 g/1
Nickel ions ca. 0.4 to 0.5 g/l
Iron ions ca. 0.005 to 0.02 g/l
Total fluoride ionsca. 660 to 715 mg/l
5 Hydro~ylamine phosphate ca. 2 g/l
Total acidity value 24 points
Free acidity value 1.6 points
RINSE STAGE
The rinse was carried out by immersion in common water at room
temperature, for 1 minute, and then in demineralized water at room
temperature, for 3 minutes.
The passivation stage was not performed in order to render more severe
the comparison of the results obtained using the aforesaid phosphatic
solutions, in the presence or in the absence of the cationic surfactant
of the invention.
The sheets underwent the above mentioned operating cycles, yelding
microcryst~ll;nP phosphate layers of even appearance.
PAINTING STAGE
The above sheets underwent a two-coats painting, according to a typical
automobile treatment:
- cathodic-epoxidic primer, polymerized at 180C for 30 minutes, yelding
a thickness of 30-35 ~m;
- alkyd-enamel topcoat, polymerized at 160C for 20 minutes, obtaining a
thickness of 35-40 ,um.
After the above mentioned operating cycles, the panels were subjected to
corrosion tests, as reported hereinbelow.
21~5 IS4
- 31 -
Corrosion Test
The coated sheets, painted as above, underwent a corrosion test according
to ASTM B 117.
After an exposure period of 1000 hours in a salt-fog room, the sub-film
penetration was measured, reporting the corrosion (mm) along incision on
either side.
TYPE OF SHEETCORROSION (mm) CORROSION (mm)
after treatment (A) after treatment (B)
Type 1 0.5-1 0.5-1
Type 2 2-3 2-3
The two different operating cycles, involving the absence or the presence
in the phosphating solution of the cationic surfactant, according to the
present invention, yeld similar and excellent results to the salt-fog
corrosion test described hereabove. These results prove that the
phosphatic films, obtained using the solutions of the invention which
prevent white spots formation, provide excellent corrosion protection
toward paint coating.
Scab Corrosion Test (Outdoor Corrosion)
The coated sheets, painted as above, underwent Scab Corrosion Test
according to FIAT standard 500412 (test method 50493/02), as described in
Example 5.
After an exposure period of 4 months, the sub-film penetration was
measured, reporting the corrosion-removal (mm) along incision on either
side. The results are as follows:
21!;5484
- 32 -
TYPE OF SHEET CORROSION (mm) CORROSION (mm)
after treatment(A) after treatment(B)
Type 1 2-3 2-3
Type 2 0-0.5 0-0.5
The max. penetration admitted by the above mentioned standard FIAT is 8
mm, after an exposure period of 4 months. The two different operating
cycles (A) and (B) yeld similar and excellent results to the scab
corrosion test described hereabove, proving that the phosphatic films,
obtained using the solutions of the invention, provide excellent
corrosion protection toward paint coating.
