REDUCING OR AVOIDING SURFACE IRREGULARITIES IN ELECTROPHORETIC PAINTING OF PHOSPHATED METAL SURFACES

Abstract: The phenomenon of "mapping" (surface defects) after electrophoretic painting over phosphate conversion coatings passivated with hexavalent chromium containing passivating compositions can be avoided or reduced by keeping the surface being treated constantly wet from the time it is conversion coated until it is electrophoretically painted, by preceding the passivating step by treatment with an aqueous liquid treatment composition comprising at least one of the following components: (A) a water soluble and/or water dispersible polymer with a weight average molecular weight of at least 500; (B) fluorometallic acids and anions thereof, the molecules of which consist of (i) at least one atom of boron, silicon, zirconium, iron, aluminum, or titanium, (ii) at least four fluorine atoms, and, optionally, (iii) one or more atoms of oxygen, hydrogen, or both; (C) zirconium salts of ethylenediamine tetraacetic acid; and (D) alkali metal and ammonium zirconyl carboxylates and carbonates; or by replacing the chromium containing passivating composition with an aqueous liquid treatment composition of the same type as described above.

Description: REDUCING OR AVOIDING SURFACE IRREGULARITIES IN ELECTROPHORETIC PAINTING OF PHOSPHATED METAL SURFACES BACKGROUND OF THE INVENTION Field of the Invention This invention relates to processes for forming a protective coating on metal, par¬ ticularly ferrous and/or zinciferous metal, surfaces by applying to the metal surfaces in order (i) a phosphate conversion coating and (ii) a cathodically or anodically deposited electrophoretic paint protective outer coating including an organic binder. More particu¬ larly, this invention is related to avoiding or at least reducing undesirable surface texture after completion of such a process. Discussion of Related Art The general type of process described above is well known and commercially very important, particularly in the automobile and related vehicle industry, in which many millions of square meters of steel and galvanized steel surfaces are protected against corrosion and provided with an aesthetically appealing surface finish by such pro ¬ cesses every year in the U. S. alone. Most often, these processes include, as a preferred optional step (i') between steps (i) and (ii) described above, contacting the conversion coating formed in step (i) with an aqueous liquid composition variously known as a seal ¬ er, "final rinse", or passivating composition. The most used such processes at present, when excellent corrosion protection is desired, are believed to be (i) phosphating with a zinc containing aqueous liquid phosphating composition, preferably one that also in- eludes manganese and, more preferably, also at least one of nickel, copper, and silver in sufficient quantities that the manganese and a third type of cations distinct from manga¬ nese and zinc, if cations of such a third type are present in the phosphating composition, are incorporated into the phosphate conversion coating layer formed in readily detectable amounts; (i 1 ) passivating by contact with a composition containing a total of at least 0.05 % of trivalent and hexavalent chromium (the latter being alternatively known as "chro- mate"), preferably containing both trivalent and hexavalent chromium; and (ii) painting with a cathodic electrophoretically applied paint (this process and the coating applied therein being usually hereinafter denoted simply as "cathodic painting" and "cathodic paint" for brevity). Ordinarily, such a process produces highly satisfactory results, but it is known in the art that such a process is susceptible occasionally, for reasons not yet understood, to a serious aesthetic defect: the presence in the final coated surface of small scale surface irregular-ties that do not correspond to any irregularities in the underlying metal surface. The occurrence of defects of this type is variously known as "mapping", which is believ- ed to be the most general term in common use in the art and will be used hereinafter to include all the terms for this effect noted below; "orange peel", when the defect is gener¬ alized small scale surface roughness analogous to that on an orange, "Naugahyde™", when the surface texture is qualitatively like orange peel but quantitatively more pro¬ nounced; and "patterning" when the irregularities occur only on some relatively small part of the total surface. Although mapping can occur with any kind of paint, experience has indicated that cathodically electrodeposited paint, which in most other respects is su¬ perior in quality to most if not all practical alternatives known at present for corrosion resistant decorative finishes such as those used for autobodies and the like, is even more susceptible to mapping, when applied over sealed phosphate conversion coatings, than other types of paint or similar protective coatings. DESCRIPTION OF THE INVENTION Objects of the Invention One major object of the invention is to avoid or at least reduce mapping while re¬ taining the other benefits known in the art for electrophoretic painting over phosphate conversion coatings, which optionally have been sealed or passivated by contact with chromate-containing or other suitable aqueous liquid compositions, before being paint¬ ed. An alternative object is to permit replacing chromate passivating treatments with other treatments less injurious to the environment, while still retaining the performance quality now achieved by phosphating, chromate passivating, and electrophoretic painting. General Principles of Description Except in the claims and the operating examples, or where otherwise expressly 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. Also, unless expressly stated to the contrary: percent, "parts of, and ratio values are by weight; the term "polymer" includes "oligomer", "copoly- mer", "terpolymer", and the like; the description of a group or class of materials as suit¬ able or preferred for a given purpose in connection with the invention implies that mix¬ tures of any two or more of the members of the group or class are equally suitable or pre¬ ferred; description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description, and does not necessarily pre- elude chemical interactions among the constituents of a mixture once mixed; specifica¬ tion 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 spec¬ ified should preferably be selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, ex- cept for avoiding counterions that act adversely to the stated objects of the invention), the term "metal surface" and its grammatical variants is to be understood as including not only bare metal surfaces but also such surfaces as modified by spontaneous reaction with the natural ambient atmosphere and/or by any prior treatment described herein; and the term "mole" and its variations may be applied to elemental, ionic, and any other chemical species defined by number and type of atoms present, as well as to compounds with well defined molecules. Summary of the Invention It has been discovered that mapping by electrophoretic, especially cathodic, paints can be reduced or avoided by properly controlling the process conditions, replac- ing a passivating composition that contains at least 0.05 % of chromium with an alterna¬ tive composition that contains not more than 0.04 % of chromium, and/or introducing an additional treatment with a suitable aqueous liquid composition that contains not more than 0.04 % of chromium before any passivating treatment composition containing at least 0.05 % of chromium is applied. More specifically, mapping may be reduced by assuring that the surface of the substrate never is allowed to become dry at any point between the completion of phos- s phate conversion coating and the beginning of electrophoretic painting, preferably by ar¬ ranging for the substrate surface to be supplied with water, preferably water purified by distillation, deionization with ion-exchange resins or reverse osmosis, or otherwise (such purified water hereinafter being usually denoted for brevity as "DI [for "deionized"] water", no matter how actually purified), at any point between these two process stages o where it otherwise might become dry. While effective, this method is often impractical to introduce into existing process lines, which usually do not have facilities in place for supplying purified water at locations between the standard operating stages. Also, the use of as much water as would be required by this method for many commercial oper¬ ations would result in substantially faster unwanted dilution of the other treatment com- 5 positions, requiring a higher and correspondingly more expensive use of replenisher compositions to maintain the desired chemical effects in process stages that can not be effectively performed by contact with water alone. Accordingly, it is normally preferred for this invention to utilize aqueous liquid treatment compositions that comprise, preferably consist essentially of, or more preferab- o ly consist of, water and at least one of the following components: (A) a water soluble and/or water dispersible polymer with a weight average molecular weight of at least 500, preferably polymer(s) of vinyl phenol(s) with partial ring substitution of hydrogen by al- kylaminomethyl moieties as taught generally in at least one of the following U. S. Patents, the complete specifications of which, except to the extent that they may be in- 5 consistent with any explicit statement herein, are hereby incorporated herein by refer¬ ence: 4,376,000, 4,433,015, 4,457,790, 4,517,028, 4,963,596, 5,063,089, 5,116,912, and 5,298,289 (these polymers being hereinafter often abbreviated as "ASPVP" for "alkyl- aminomethyl substituted poly{ vinyl phenol}"); (B) fluorometallic acids and anions there¬ of, the molecules of which consist of (i) at least one atom of boron, silicon, zirconium, 0 iron, aluminum, or titanium, (ii) at least four fluorine atoms, and, optionally, (iii) one or more atoms of oxygen, hydrogen, or both; (C) zirconium salts of ethylenediamine tetra- acetic acid; and (D) alkali metal and ammonium salts of zirconium hydroxycarboxylates and zirconium hydroxycarbonates (alternatively called alkali metal and ammonium zirconyl carboxylates and carbonates). These aqueous liquid treatment compositions may entirely replace any passivating compositions formerly used that contained as much as 0.05 % of chromium, or they may be used after the phosphate conversion coating but before treatment with a conventional chromium containing passivating composition, tak¬ ing care to prevent drying of the treated surfaces between use of the aqueous liquid treat¬ ment composition and contact of the surface with any chromium containing passivating composition. Description of Preferred Embodiments For a variety of reasons, it is preferred that aqueous liquid treatment compositions according to the invention as defined above should be substantially free from certain in¬ gredients used in compositions for similar purposes in the prior art. Specifically, it is in¬ creasingly preferred in the order given, independently for each preferably minimized component listed below, that these compositions, when directly contacted with metal in a process according to this invention, contain no more than 1.0, 0.35, 0J0, 0.08, 0.06, 0.04, 0.03, 0.02, 0.01, 0.007, 0.003, 0.001, 0.0007, 0.004, or 0.0002, percent of each of cyanide and nitrite ions, and, unless its use is required for the particular use to be made of substrates treated according to the invention, chromium should also be minimized.. Furthermore, in a process according to the invention that includes other steps than treating a metal surface with a composition as described above, it is normally preferred that none of these other steps include contacting the surfaces with any composition that contains more than, with increasing preference in the order given, 1.0, 0.35, 0J0, 0.08, 0.04, 0.02, 0.01, 0.003, 0.001, or 0.0002 % of hexavalent chromium, except that a final protective coating system including an organic binder, more particularly those including a primer coat, may include hexavalent chromium as a constituent. Any such hexavalent chromium in the protective coating is generally adequately confined by the organic binder, so as to avoid adverse environmental impact. A working ASPVP composition for use in a process according to this invention preferably comprises, more preferably consists essentially of, or still more preferably consists of; water, water soluble polymer and/or acid salts thereof as described in column 3 lines 5 through 64 of U. S. Patent 4,443,015, and, optionally, one or more fluorometal- lic acids or anions thereof as defined above. The total amount of ASPVP and acid salts thereof dissolved in the aqueous working composition preferably is, with increasing pref¬ erence in the order given, at least 0.004, 0.008, 0.016, 0.030, 0.040, 0.050, 0.055, 0.060, 0.065, 0.070, 0.073, 0.076, 0.079, 0.081, 0.082, 0.083, or 0.084 %, and independently preferably is, with increasing preference in the order given, not more than 10, 5, 3, 2, 1, s 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.30, 0.25, 0.22, 0.20, 0J8, 0J6, 0J4, 0.12, 0J0, or 0.09 %. (The preferred upper limits as noted above are preferred primarily for economic reasons. No adverse effect on quality is known from even higher concentrations, but such concen¬ trations also do not further improve quality and result in more waste. In contrast to this, concentrations lower than those noted above as preferred may result in less effective cor- o rosion protection.) The molar ratio of nitrogen atoms to aromatic rings in an ASPVP working com¬ position for use in a process according to this invention for replacing or preceding a chromium containing passivating treatment preferably is, with increasing preference in the order given, not less than 0J0, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.85, 0.90, s 0.93, 0.95, or 0.96 and independently preferably is, with increasing preference in the order given, not more than 2.0, 1.5, 1.4, 1.3, 1.2, 1.15, 1.10, 1.05, or 1.00. Independently, the nitrogen atoms in the water soluble polymer and/or salts thereof in the ASPVP working composition for use in a process according to this invention for replacing or preceding a chromium containing passivating treatment preferably is chemically bonded to the aromatic rings in said polymer via a methylene moiety and is chemically bonded to two other organic moieties, each of which independently is preferably selected from the group consisting of alkyl and hydroxyalkyl moieties. Independently, these alkyl and hydroxyalkyl moieties preferably have not more than, with increasing preference in the order given, 10, 6, 5, 4, 3, or 2 carbon atoms each. Also independently, the two alkyl or 5 substituted alkyl moieties attached to each nitrogen atom preferably include at least one, more preferably exactly one, hydroxyalkyl moiety containing a single hydroxyl moiety The pH of an ASPVP working composition for use in a process according to this invention for replacing or preceding a chromium containing passivating treatment prefer¬ ably is, with increasing preference in the order given, at least 0.5, 1.5, 2.5, 3.5, 4.0, 4.3, 4.5, 4.7, 4.8, 4.9, or 5.0 and independently preferably is, with increasing preference in the order given, not more than 12, 11, 10, 9, 8.5, 8.0, 7.7, 7.4, 7.2, 7.0, 6.8, 6.6, 6.4, 6.3, 6.2, 6J, or 6.0. Normally, achieving the most preferred pH values as thus defined will require the presence in the composition of at least some acid salt in addition to neutral polymer. The acid part of such acid salt may be selected as taught in the U. S. Patents incorporated herein by reference above. It is particularly preferred that, with increasing preference in the order given, at least 0.002, 0.004, 0.006, 0.008, 0.010, 0.012, 0.014, 0.016, or 0.017 of the total ASPVP working composition according to the invention be constituted by fluotitanic acid and/or acid salts thereof with the alkylaminomethyl ring substituted polymers of vinyl phenol already described. Higher concentrations than these of fluotitanic acid are not deleterious but are more expensive than other acids such as phosphoric and nitric that appear to give equally good performance when substituted for any higher amounts of fluotitanic acid that might be needed to achieve the most preferab¬ le pH values for the compositions. The time of contact between a phosphate coated metal surface and an aqueous li¬ quid treatment composition according to this invention preferably is, with increasing preference in the order given, not less than 2, 4, 8, 12, 15, 18, 21, 24, 26, 28, or 30 sec- onds and independently preferably is, with increasing preference in the order given, not more than 600, 300, 200, 100, 75, 60, 50, 45, 40, 35, or 32 seconds. (The preferred upper limits are preferred primarily for economy of operation; it is not expected that long con¬ tact times will have any deleterious effect on the quality of the protection achieved in a process according to the invention. Shorter contact times than those preferred, on the other hand, may lead to inadequate protection.) The temperature of the treatment compo¬ sition used according to the invention preferably is, with increasing preference in the order given, not less than 10, 15, or 20 c C and independently preferably is, with increas¬ ing preference in the order given, not more than 80, 70, 60, 50, 45, 40, 35, or 30 β C Although ASPVP containing compositions are most preferred, a wide variety of other compositions may be used. Among these other types of somewhat less preferred but suitable compositions are: Compositions comprising, preferably consisting essentially of, or more preferabK consisting of water, soluble zirconium compounds and a water soluble and/or spontaneously water dispersible polymer as described in U. S. Patent 3,912,548 of Oct. 14, 1975 to Faigen, the following portions of which, except to the extent that they may be contrary to any explicit statement herein, are hereby incorporat¬ ed herein by reference: Column 2 line 7 through column 4 line 13; column 5 lines 39 through 65; column 6 lines 5 through 33; Example 1; column 9, last para¬ graph; and the compositions in Tables 9 and 10, together with the sentences that run from line 23 through line 27 and from lines 56 - 60 of column 16. Compositions comprising, preferably consisting essentially of, or more preferably consisting of (i) water, (ii) from 0.2 to 8 g/L of at least one acid selected from the group consisting of H 2 ZrF 6 , H 2 TiF 6 , and H 2 SiF 6 , and (iii) from 0.5 to 10 g/L of polymers selected from the group consisting of polyacrylic acid and esters thereof, as described in U. S. Patent 4,191,596 of March 4J980 to Dollman et al., the following portions of which, except to the extent that they may be contrary to any explicit statement herein, are hereby incorporated herein by reference: column 2 lines 14 to 26; column 2 line 47 through column 3 line 55; and the compositions given in Tables 1 and 2. Compositions comprising, preferably consisting essentially of, or more preferably consisting of (i) water, (ii) from 0.03 to 0.9 g/L of a water soluble first polymer having a plurality of carboxyl functional groups, and (iii) from 0.01 to 0.6 g/L of a water soluble second polymer having a plurality of hydroxyl groups, the ratio of moles of carboxyl groups to moles of hydroxyl functional groups provided by these water soluble polymers being from 0.3: 1.0 to 3.5: 1.0, and, optionally but preferably, (iv) from 0.7 to 3.0 g/L in total of at least one of (iv. l) zirconium and titanium salts of ethylenediamine tetraacetic acid, (iv.2) alkali metal and ammoni¬ um salts of zirconium and titanium hydroxycarboxylates and zirconium and titan¬ ium hydroxycarbonates, and (iv.3) fluorometallic acids and anions thereof, the molecues of which consist of (iv.3.i) at least one atom of zirconium or titanium, (iv.3.ii) six fluorine atoms, and, optionally, (iv.3.iii) one or more atoms of hy- drogen. These compositions and equivalent ones with only a single difunctional type of polymer are described in more detail in International Patent Application PCT US93/1 1627, the specification of which was published as WO94/12570 on 9 June 1994. For any process steps other than contact with a treatment composition according to the invention that may be a part of a process according to this invention, the preferred conditions are generally those known er se for the same or a similar process step in the prior art. The invention may be further appreciated by consideration of the following non- limiting working examples and comparison examples. Example and Comparison Example Group 1 A commercial automobile manufacturing plant, in which automobile bodies are subjected successively to phosphating with BONDERITE® 958 1 zinc-manganese-nickel phosphating solution, rinsing, passivating with PARCOLENE® 60 1 mixed hexavalent and trivalent chromium containing liquid composition, rinsing, and painting with Catho- gard™ 200 2 cathodically applied paint, normally operates successfully with no mapping problem. However, on a particular day observed by one applicant inventor here, every automobile hood processed for several hours was observed to have in the paint finish a narrow line of coating thinner than the surrounding coating, indicative of locally lower electrical conductivity, even though all specified conditions of the processing steps were being controlled within their customary tolerance limits which do not result in mapping on most days. The line defect in the paint observed on the day in question matched in location a line observed around the air scoop cutouts on the hood during the drying pat¬ tern after rinsing with DI water following the phosphating step. (The line speed and dis¬ tance between process stages in this manufacturing plant are such that complete drying of at least part of the surfaces normally occurs between the time of entry to the passivat¬ ing composition spray zone and the last preceding water rinse before such entry and also occurs again between emergence from the passivating composition spray zone and a DI water spray rinse zone located 30 meters ahead of the entry to the paint coating tank Drying does not normally occur between this last mentioned rinse and the entry to the paint coating tank.) The following improvised measures were attempted to correct this mapping prob- lem, with the results indicated: 1J . The hoods were flooded with a large mass of DI water prior to entering the DI water spray rinse zone located 10 meters ahead of the entry to the paint coating tank This rewetting did not reduce the mapping pattern. Commercially available from the Parker Amchem Division of Henkel Corp., Madison Heights, Michigan. Commercially available from BASF Corporation. 1.2. The area of the hoods on which the mapping defect was occurring was wiped with a solvent saturated cloth at about the same point in the production line as noted for item 1 J . Again, this did not reduce the mapping problem. 1.3. DI water was applied as needed at every point along the production line between s exit from the phosphating immersion tank to entry into the paint immersion tank, in order to assure that the surface never became dry during this time. This measure completely eliminated the mapping problem, even though autobodies otherwise identically processed both before and after the bodies on which this constant wetting was maintained showed the same mapping line defect problem as before. o 1.4. An ASPVP containing composition containing the following ingredients in addi¬ tion to deionized water was prepared: (i) 0.085 % of a high molecular weight organic material produced by reacting a homopolymer of 4-vinyl phenol having an average mo¬ lecular weight of about 5000 with sufficient amounts of methyl ethanol amine and for¬ maldehyde to substitute an average of 0.97 N,N-methyl-2-hydroxyethylaminomethyl s moieties per aromatic ring for hydrogen atoms on the aromatic rings in the homopolymer starting material; 3 (ii) 0.029 % of orthophosphoric acid; (iii) 0.0047 % of sodium hydrox¬ ide; and (iv) 0.018 % of fluotitanic acid. This ASPVP containing composition was ap¬ plied to the autobodies just after they had passed through the DI water spray rinse zone located 10 meters ahead of the entry to the paint coating tank. This rewetting did not re- 0 duce the mapping pattern. 1.5. The same ASPVP composition as described in item 1.4 was applied to the auto¬ bodies just prior to the process zone where the PARCOLENE® 60 spray coating was ap¬ plied. The mapping problem was eliminated, even though other autobodies processed immediately before and after this test showed the mapping pattern. 5 US, This was the same as item 1.5, except that the PARCOLENE® 60 spray coating was discontinued. The mapping problem was again eliminated. Example and Comparison Example Group 2 For this group, panels of electrogalvanized iron-zinc alloy, which is known to be exceptionally sensitive to mapping problems with cathodically electrodeposited paint. 3 Such a polymer may be prepared according to the teachings of the U. S. Patents incorporated by reference into this specification. were used. Many such panels were coated in a laboratory process unit by the steps shown in Table 1 below, except that only one of the three possible passivating steps noted in the Table was performed on any one test panel, and on some of the test panels, no passivating treatment at all was applied. Panels with each type of laboratory-applied passivating treatment shown in Table 1 and other panels with no passivating treatment were then attached to actual automobile bodies in such a manner that the panel had the same angle to the ground, specifically nearly horizontal, as the hood areas on these autobodies that were known from prior ex¬ perience to be most susceptible to developing a mapping defect. The test panels with laboratory applied passivating treatments and some of the test panels without laboratory applied passivating treatments were attached to the auto¬ bodies just after the latter had emerged from the sprayed passivating treatment area of the normal production operation, while other test panels with no laboratory passivating treatment were attached to the autobodies at an earlier point in the process sequence, just before the normal plant passivating operation, so that they were exposed to the same plant applied processing treatment as the autobodies to which they were attached. All these types of attached panels were then subjected to all of the subsequent treatments applied to the autobodies after the point in the process line at which they were attached to the autobodies, including eventual cathodically applied painting, during a time period when normal production operations were resulting in no evident mapping defect on most of the autobodies finished. (These autobodies were made of a substrate metal less susceptible to mapping defects than the electrogalvanized zinc-iron alloy used for the test panels.) As a final variation in this group, for some of the hoods, the passivat¬ ing treatment spray was turned of-ζ so that there was no passivating treatment at all. The passivating treatment composition sprayed by the normal plant equipment during this test was substantially the same as is described for "Pas. #2" in Table 1. The results of these tests are shown in Table 2 below. Table 1 Notes for Table 1 All of the mgredients necessary to make the workmg compositions the table that are identified by one of the trademarks PARCO®, FIXODINE®, BONDERITE®, and PARCOLENE® are commercially available from the Parker Amchem Div. of Henkel Corp., Madison Heights. Michi¬ gan, along with directions and apparatus for preparing workmg compositions and performmg the tests used to characterize these working compositions by "points" as used m the table above "Pas " is an abbreviation for "Passivatmg Composition" The active ingredient in Passivatmg Composition #2 is tπvalent chromium Use of Passivatmg Composition #3 is according to the present mvenϋon, while use of Passivatmg Compositions # 1 and 2 is not In the column headed "Contact Method", "S" means spraying and "I" means immersion Table 2 Nature of Sample Degree of Mapping Observed Hoods, normal production None Panels, phosphated in lab, passivated in Slight plant only Panels, phosphated and Pas. #1 in lab Slight Panels, phosphated and Pas. #2 in lab Moderate Panels, phosphated and Pas. #3 in lab None; best overall appearance Hoods, no passivating treatment None Examples Group 3 The following compositions, with alternative solutes not including any ASPVP, are used in the same general manner as is described in Examples and Comparison Examples Groups 1 and 2 above for the ASPVP containing treatment compositions there described, in order to reduce or prevent mapping: 3.1 : A composition containing ammonium zirconyl carbonate in an amount stoichiomet- rically equivalent to 2.0 g/L of ZrO 2 and 2.8 g/L of polyacrylic acid 4 , with the balance water. 3.2: A composition with a pH of 2J, containing 4.11 g/L of polyacrylic acid 4 and 1.23 g/L of fluozirconic acid, with the balance water. 3.3 : A composition with a pH of 2.1, containing 4.11 g/L of polyacrylic acid 4 and 1.94 g/L of fluotitanic acid, with the balance water. 3.4: A composition with a pH of 2.2, containing 2.05 g/L of polyacrylic acid 4 and 0.97 g/L of fluotitanic acid, with the balance water. 3.5: A composition with a pH of 2J, containing 4.11 g/L of polyacrylic acid 4 and 0.85 g/L of fluosilicic acid, with the balance water. 4 From a latex commercially supplied by Rohm & Haas under the designation ACUMER™ 1510. 3.6: A composition containing 2 % by volume of a first subcomposition, which consists of 1.46 % polyvinyl alcohoP, 2.28 % of polyacrylic acid 4 , 0.05 % of ammonium bifluor- ide, and 96.21 % of water; 2 % by volume of a second subcomposition, which consists of 7.4 % of fluozirconic acid, 0.3 % of hydrofluoric acid, and 92.3 % water; and a bal- s ance of water. 3.7: A composition that is like 3.6, except that ammonium zirconyl carbonate is substi¬ tuted for the fluozirconic acid in composition 3.6, in an amount so as to result in the same concentration of zirconium atoms in the composition as in Composition 3.6. 'Commercially supplied by Air Products & Chemicals, Inc. under the designation AIRVOL™ 125

Claims: The invention claimed is: 1. A process of forming a protective coating on a metal surface, said process compris¬ ing steps of: (I) contacting the metal surface with an aqueous liquid phosphate conversion coating composition and (II) subsequent to step (I), applying to the metal surface an electrophoretic paint pro¬ tective outer coating, wherein the improvement comprises at least one of the following: (A) maintaining the treated surface of the metal continuously wet from the time of dis- continuance of contact with the aqueous liquid phosphate conversion coating com¬ position until applying the electrophoretic paint protective outer coating; and (B) contacting the metal surface after performing step (I) and before performing step (II) with an aqueous liquid treatment composition comprising water, not more than 0.04 % of chromium, and at least one of the following components: (BJ) a water soluble, water dispersible, or both water soluble and water dispersible polymer with a weight average molecular weight of at least 500; (B.2) fluorometallic acids and anions thereof consisting of (B.2.i) at least one atom of boron, silicon, zirconium, iron, aluminum, and titanium, (B.2.ii) at least four fluorine atoms, and, optionally, (B.2.ϋi) one or more atoms of oxygen, hydrogen, or both; (B.3) zirconium salts of ethylenediamine tetraacetic acid; and (B.4) alkali metal and ammonium salts of zir¬ conium hydroxycarboxylates and zirconium hydroxycarbonates 2. A process according to claim 1, wherein the electrophoretic paint is cathodically electrodeposited; the process comprises a step (B) of contacting the metal surface after performing step (I) and before performing step (II) with an aqueous liquid treatment composition comprising water, not more than 0.04 % of chromium, and a total of at least about 0.004 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof; and the process optionally also comprises a step (B 1 ), performed after step (B) but before step (II), of contacting the metal surface with a phosphate conversion coating passivating composition comprising at least 0.05 % of chromium. 3. A process according to claim 2, wherein the phosphate conversion coating compo¬ sition is a zinc phosphating composition. 4. A process according to claim 3, wherein the phosphate conversion coating compo¬ sition contains manganese and manganese is incorporated into the conversion coating formed. 5. A process according to claim 4, wherein the phosphate conversion coating compo- 5 sition contains nickel and nickel is incorporated into the conversion coating formed. 6. A process according to claim 5, wherein the aqueous liquid treatment composition used in step (B) is a chromium free aqueous liquid ASPVP containing composition that has a pH in the range from about 4.0 to about 9 and comprises a total of from about 0.050 to about 0.5 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts o thereof. 7. A process according to claim 6, wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from 4.5 to 7.0 and contains a total of from about 0.060 to about 0J 8 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof in which the nitrogen atoms in the alkylaminomethyl groups are chem- 5 ically bonded to aromatic rings in said polymer through methylene groups and are also chemically bonded to two other organic moieties selected from the group consisting of alkyl and hydroxyalkyl moieties with no more than 4 carbon atoms each, the molar ratio of nitrogen atoms to aromatic rings in the substituted polymers of vinyl phenol being from about 0.5 to about 1.5. 0 8. A process according to claim 7, wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from about 4.7 to about 6.4 and the nitrogen atoms in the alkylaminomethylene groups are also bonded to two organic moieties selected from the group consisting of alkyl and hydroxyaikyi moieties with no more than 2 carbon atoms and one hydroxyl moiety each, the molar ratio of nitrogen atoms to aromatic rings 5 in the substituted polymers of vinyl phenol being from about 0.70 to about 1.3. 9. A process according to claim 8, wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from about 5.0 to about 6.0 and comprises from about 0.076 to about 0J2 % of N,N-methyl-2-aminoethylaminomethyl substituted poly¬ mers of vinyl phenol, the time of contact between the phosphated metal surface and said o aqueous liquid treatment composition is from about 24 to about 45 seconds and the tem¬ perature during this contact is from about 20 to about 30 ° C, and the molar ratio of ni- trogen atoms to aromatic rings in the substituted polymers of vinyl phenol is from about 0.90 to about 1 J0. 10. A process according to claim 3, wherein the aqueous liquid treatment composition used in step (B) is a chromium free aqueous liquid ASPVP containing composition that s has a pH in the range from about 4.0 to about 9 and comprises a total of from about 0.050 to about 0.5 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof. 11. A process according to claim 10, wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from 4.5 to 7.0 and contains a total of from about o 0.060 to about 0J8 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof in which the nitrogen atoms in the alkylaminomethyl groups are chem¬ ically bonded to aromatic rings in said polymer through methylene groups and are also chemically bonded to two other organic moieties selected from the group consisting of alkyl and hydroxyalkyl moieties with no more than 4 carbon atoms each, the molar ratio of nitrogen atoms to aromatic rings in the substituted polymers of vinyl phenol being from about 0.5 to about 1.5. 12. A process according to claim 11 , wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from about 5.0 to about 6.0 and comprises from about 0.076 to about 0J2 % of N,N-methyl-2-aminoethylaminomethyl substituted poly- mers of vinyl phenol, the time of contact between the phosphated metal surface and said aqueous liquid treatment composition is from about 24 to about 45 seconds and the tem¬ perature during this contact is from about 20 to about 30 ° C, and the molar ratio of ni¬ trogen atoms to aromatic rings in the substituted polymers of vinyl phenol is from about 0.90 to about 1J0. 13. A process according to claim 2, wherein the aqueous liquid treatment composition used in step (B) is a chromium free aqueous liquid ASPVP containing composition that has a pH in the range from about 4.0 to about 9 and comprises a total of from about 0.050 to about 0.5 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof. 14. A process according to claim 13, wherein the aqueous liquid treatment composition used in step (B) has a pH in the range from 4.5 to 7.0 and contains a total of from about 0.060 to about 0J8 % of alkylaminomethyl substituted polymers of vinyl phenol and acid salts thereof in which the nitrogen atoms in the alkylaminomethyl groups are chem¬ ically bonded to aromatic rings in said polymer through methylene groups and are also chemically bonded to two other organic moieties selected from the group consisting of alkyl and hydroxyalkyl moieties with no more than 4 carbon atoms each, the molar ratio of nitrogen atoms to aromatic rings in the substituted polymers of vinyl phenol being from about 0.5 to about 1.5. 15. A process according to claim 1, said process comprising a step (B) of contacting the metal surface after performing step (I) and before performing step (II) with an aque- ous liquid treatment composition consisting essentially of (i) water, (ii) not more than 0.04 % of chromium, (iii) from about 0.1 to about 3.5 g/L, measured as its stoichiometric equivalent as zirconium dioxide, of a dissolved zirconium compound selected from the group consisting of alkali metal and ammonium fluozirconates and alkali metal and am¬ monium z-rconium hydroxycarboxylates and carbonates, and (iv) from about 0J to about 5.0 g/L in total of dissolved material selected from the group consisting of polyacrylic acid and the esters and salts thereof, poly{ vinyl alcohol}, hydroxyethyl ethers of cellu¬ lose, copolymers of ethylene and maleic anhydride, poly{vinyl pyrrolidone}, and poly- { vinyl methyl ether}; and optionally also comprising a step (B 1 ), performed after step (B) but before step (Η), of contacting the metal surface with a phosphate conversion coating passivating composition comprising at least 0.05 % of chromium. 16. A process according to claim 15, wherein, in the aqueous liquid treatment composi¬ tion used in step (B), component (iii) is ammonium zirconyl carbonate, component (iv) is selected from the group consisting of polyacrylic acid and the esters and salts thereof, and the amount of component (iv) is from about 1.0 to about 2.0 times the amount of zir- conium in the aqueous liquid treatment composition. 17. A process according to claim 1, said process comprising a step (B) of contacting the metal surface after performing step (I) and before performing step (II) with an aque¬ ous liquid treatment composition consisting essentially of (i) water, (ii) not more than 0.04 % of chromium, (iii) from about 0.2 to about 8 g/L of at least one acid selected from the group consisting of H^rF^ H 2 TiF 6 , and H 2 SiF 6 , and (iv) from about 0.5 to about 10 g/L of polymers selected from the group consisting of polyacrylic acid and esters thereof; and optionally also comprising a step (B'), performed after step (B) but before step (II), of contacting the metal surface with a phosphate conversion coating passivating composi¬ tion comprising at least 0.05 % of chromium. 18. A process according to claim 17, wherein, in the aqueous liquid treatment composi- tion used in step (B), the content of component (iii) is from about 1.5 to about 6.0 g/L and the content of component (iv) is from about 0.75 to about 4.0 g/L. 19. A process according to claim 1, said process comprising a step (B) of contacting the metal surface after performing step (I) and before performing step (II) with an aque¬ ous liquid treatment composition consisting essentially of (i) water, (ii) not more than 0.04 % of chromium, (iii) from about 0.03 to about 0.9 g/L of a water soluble first poly¬ mer having a plurality of carboxyl functional groups, and (iv) from about 0.01 to about 0.6 g/L of a water soluble second polymer having a plurality of hydroxyl groups, the ratio of moles of carboxyl groups to moles of hydroxyl functional groups provided by these water soluble polymers being from 0.3: 1.0 to 3.5: 1.0; and optionally also comprising a step (B'), performed after step (B) but before step (II), of contacting the metal surface with a phosphate conversion coating passivating composition comprising at least 0.05 % of chromium. 20. A process according to claim 19, wherein the aqueous liquid treatment composition used in step (B) also comprises (v) from 0.7 to 3.0 g/L in total of at least one of (v. l) zir- conium and titanium salts of ethylenediamine tetraacetic acid, (v.2) alkali metal and am¬ monium salts of zirconium and titanium hydroxycarboxylates and zirconium and titanium hydroxycarbonates, and (v.3) fluorometallic acids and anions thereof, the molecules of which consist of (v.3.i) at least one atom of zirconium or titanium, (v 3 ii) six fluorine atoms, and, optionally, (v.3.iii) one or more atoms of hydrogen.

Inventors: STEINBRECHER LESTER E, ZENS TIMOTHY J, STEINBRECHER, LESTER, E., ZENS, TIMOTHY, J.
Applicants: HENKEL CORP, HENKEL CORPORATION
Application year: 1996
Main classification: C25D13
IPC codes: C23C22, C25D13