Composition and process for treating metal

Abstract

Heating an aqueous mixture of a fluoroacid such as H.sub.2 TiF.sub.6 and an oxide, hydroxide, and/or carbonate such as silica produces a clear mixture with long term stability against settling of any solid phase, even when the oxide, hydroxide, or carbonate phase before heating was a dispersed solid with sufficiently large particles to scatter light and make the mixture before heating cloudy. The clear mixture produced by heating can either be mixed e with water soluble and/or water dispersible polymers that are polyhydroxyalkylamino- substituted polymers and/or copolymers of p-vinyl phenol, or with soluble hexavalent and/or trivalent chromium, to produce a composition that improves the corrosion resistance of metals treated with the composition, especially after subsequent painting.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to processes of treating metal surfaces with aqueous acidic compositions to increase the resistance to corrosion of the treated metal surface, either as thus treated or after subsequent overcoating with some conventional organic based protective layer. A major object of the invention is to provide a storage stable, single package treatment that can be substantially free from hexavalent chromium but can protect metals substantially as well as the hexavalent chromium containing treatments of the prior art, or can improve the stability of treatment solutions that do contain hexavalent chromium.

2. Statement of Related Art

A very wide variety of materials have been taught in the prior art for the general purposes of the present invention, but most of them contain hexavalent chromium or other inorganic oxidizing agents which are environmentally undesirable. The specific items of related art believed by the applicant to be most nearly related to the present invention are noted below.

U.S. Pat. No. 5,089,064 of Feb. 18, 1992 to Reghi teaches a process for treating aluminum with a composition containing fluozirconic acid (H.sub.2 ZrF.sub.6), a water soluble or dispersible polymer of 3-(N-C.sub.1-4 alkyl-N-2-hydroxyethylaminomethyl)-4-hydroxystyrene, and dispersed silica. This treatment produces excellent results, but is somewhat inconvenient because the treating composition is susceptible to slow settling of the dispersed silica component. In practice, this means that for best results, at least two components, one with the silica and one without, must be stored separately and mixed shortly before use.

U.S. Pat. No. 4,963,596 of Oct. 16, 1990 to Lindert et al. teaches the use of water soluble derivatives of poly {vinyl phenol} in metal treating, including combinations of these polymer materials with dispersed silica among many other possibilities.

U.S. Pat. No. 4,921,552 of May 1, 1990 to Sander et al. teaches treating aluminum with a composition comprising fluozirconic acid, hydrofluoric acid, and a water soluble polymer.

Published European Patent Application 0 273 698 (published Jul. 6, 1988) teaches aqueous acidic treating solutions comprising trivalent metal compounds, silica, and preferably also nickel and/or fluoride ions. The counter anions for the trivalent metal cations used may be silicofluoride.

U.S. Pat. No. 4,341,558 of Jul. 27, 1982 to Yashiro et al. teaches treating metal surfaces with a composition containing a water soluble salt of zirconium and/or titanium, an inositol phosphate ester, and silica. The composition may also contain an organic binder such as poly{vinyl alcohol}.

U.S. Pat. No. 4,277,292 of Jul. 7, 1982 to Tupper teaches treating aluminum surfaces with an aqueous acidic composition containing zirconium, fluoride, and vegetable tannin.

U.S. Pat. No. 3,506,499 of Apr. 14, 1970 to Okada et al. teaches treating aluminum and zinc surfaces with an aqueous solution of chromic acid and colloidal silica.

S. M. Thomsen, "High-Silica Fluosilic Acids: Specific Reactions and the Equilibrium with Silica", Jour. Amer. Chem. Soc. 74, 1690-93 (1952), according to an abstract thereof, teaches that high-silica fluosilic acids can be prepared with any desired amount of "extra" silica up to 18% more than the composition given by the formula H.sub.2 SiF.sub.6, by dissolving hydrated silica in hydrofluoric acid. The high silica fluosilic acids show characteristic reactions with sodium salts and fluorides. A hypothesized chemical equilibrium: 4H.sup.+ +5SiF.sub.6.sup.-2 +SiO.sub.2 --3(SiF.sub.6 --SiF.sub.4).sup.-2 +2H.sub.2 O was found to have an equilibrium constant of about 100-10,000.

DESCRIPTION OF THE INVENTION

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 exact numerical limits stated is generally preferred.

SUMMARY OF THE INVENTION

It has been found that aqueous compositions comprising (A) a component of dissolved fluoroacids of one or more metals and metalloid elements selected from the group of elements consisting of titanium, zirconium, hafnium, boron, silicon, germanium, and tin and (B) a component of one or more of (i) dissolved or dispersed forms of metals and metalloid elements selected from the group of elements consisting of titanium, zirconium, hafnium, boron, aluminum, silicon, germanium, and tin and (ii) the oxides, hydroxides, and carbonates of such metals and metalloid elements can be converted by mixing for practical reaction times into an aqueous composition with long term stability against spontaneous settling or precipitation, even when the metallic and/or metalloid elements, oxides, hydroxides, and/or carbonates present in the compositions are in the form of dispersed solids that would settle if stored for even a few days without ever having been reacted.

These compositions prepared with mixing are then combined with either (i) a water soluble or dispersible polymer and/or copolymer of one or more x-(N-R.sup.1 -N-R.sup.2 -aminomethyl)-4-hydroxy-styrenes, where x=2, 4, 5, or 6, R.sup.1 represents an alkyl group containing from 1 to 4 carbon atoms, preferably a methyl group, and R.sup.2 represents a substituent group conforming to the general formula H(CHOH).sub.n --, where n is an integer from 3 to 8, preferably from 4 to 6, or (ii) a composition contain hexavalent chromium, and, optionally but preferably, trivalent chromium. The resulting compositions are suitable for treating metal surfaces to achieve excellent resistance to corrosion, particularly after subsequent conventional coating with an organic binder containing protective coating. The compositions are particularly useful on iron and steel, galvanized iron and steel, zinc and those of its alloys that contain at least 50 atomic percent zinc, and, most preferably, aluminum and its alloys that contain at least 50 atomic percent aluminum. The treating may consist either of coating the metal with a liquid film of the composition and then drying this liquid film in place on the surface of the metal, or simply contacting the metal with the composition for a sufficient time to produce an improvement in the resistance of the surface to corrosion, and subsequently rinsing before drying. Such contact may be achieved by spraying, immersion, and the like as known per se in the art.

It should be understood that this description does not preclude the possibility of unspecified chemical interactions among the components listed, but instead describes the components of a composition according to the invention in the form in which they are generally used as ingredients to prepare such a composition.

DESCRIPTION OF PREFERRED EMBODIMENTS

To the extent that their water solubility is sufficient, the fluoroacid component [hereinafter sometimes denoted by "(A)"] to be reacted in a process according to one embodiment of the invention may be freely selected from the group consisting of H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 HfF.sub.6, H.sub.2 SiF.sub.6, H.sub.2 GeF.sub.6, H.sub.2 SnF.sub.6, HBF.sub.4, and mixtures thereof. H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 HfF.sub.6, H.sub.2 SiF.sub.6, HBF.sub.4, and mixtures thereof are preferred; H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 SiF.sub.6 and mixtures thereof are more preferred; and H.sub.2 TiF.sub.6 is most preferred. The concentration of fluoroacid component at the time of reaction is preferably between 0.01 and 7 moles per liter (hereinafter "M"), more preferably between 0.1 and 6 M.

The component [hereinafter sometimes denoted "(B)"] of metallic and/or metalloid elements and/or their oxides, hydroxides, and/or carbonates is preferably selected from the group consisting of the oxides, hydroxides, and/or carbonates of silicon, zirconium, and/or aluminum and more preferably includes silica. Any form of this component that is sufficiently finely divided to be readily dispersed in water may be used in a process according to one embodiment of this invention, but for constituents of this component that have low solubility in water it is preferred that the constituent be amorphous rather than crystalline, because crystalline constituents can require a much longer period of heating and/or a higher temperature of heating to produce a composition no longer susceptible to settling. Solutions and/or sols such as silicic acid sols may be used, but it is highly preferable that they be substantially free from alkali metal ions as described further below. However, it is generally most preferred to use dispersions of silica made by pyrogenic processes.

An equivalent of a metallic or metalloid element or of its oxide, hydroxide, or carbonate is defined for the purposes of this description as the amount of the material containing a total of Avogadro's Number (i.e., 6.02.times.10.sup.23) total atoms of metal and/or metalloid elements from the group consisting of Ti, Zr, Hf, B, Al, Si, Ge, and Sn. The ratio of moles of fluoroacid component (A) to total equivalents of component (B) in an aqueous composition heated according to one embodiment of this invention preferably is from 1:1 to 50:1, more preferably from 1.5:1.0 to 20:1, or still more preferably from 1.5:1 to 5.0:1.0. If desired, a constituent of this component may be treated on its surface with a silane coupling agent or the like which makes the surface oleophilic.

According to one embodiment of the invention, an aqueous composition comprising, preferably consisting essentially of, or more preferably consisting of water and the fluoroacid component and the metallic and/or metalloid element(s) oxide(s), hydroxide(s), and/or carbonate(s) component as described above is agitated for a sufficient time to produce a composition that does not suffer any visually detectable settling when stored for a period of 100, or more preferably 1000, hours. Preferably, during agitation the temperature is in the range from 25.degree. to 100.degree. C., or more preferably within the range from 30.degree. to 80.degree. C., and the time that the composition is maintained within this temperature is within the range from 3 to 480, more preferably from 5 to 90, still more preferably from 10 to 30, minutes (hereinafter often abbreviated "min"). Shorter times and lower temperatures within these ranges are generally better for converting compositions in which the component (B) is selected only from dissolved species and/or dispersed amorphous species without any surface treatment to reduce their hydrophilicity, while longer times and/or higher temperatures within these ranges are likely to be needed if component (B) includes dispersed solid crystalline materials and/or solids with surfaces treated to reduce their hydrophilicity. With suitable equipment for pressurizing the reaction mixture, even higher temperatures than 100.degree. C. can be used in especially difficult cases.

Independently, it is preferred that the pH of the composition combining components (A) and (B) as described above be kept in the range from 0 to 4, more preferably in the range from 0.0 to 2.0, or still more preferably in the range from 0.0 to 1.0 before temperature maintenance as described above.

Preferably after maintenance at a temperature as described above, the composition is brought to a temperature below 30.degree. C. and then mixed with a component [hereinafter sometimes denoted "(C)"] consisting of either (1) water soluble or water dispersible polyhydroxyl alkylamino derivatives of poly{p-hydroxystyrene} as deccribed above and in more detail in U.S. Pat. No. 4,963,596, the entire specification of which, except to the extent contrary to any explicit statement herein, is hereby incorporated herein by reference or (2) hexavalent chromium, and optionally but preferably, trivalent chromium solutions as known per se in the art for treating metals, particularly aluminum and its alloys, to retard corrosion thereon. Suitable and preferred polymers and methods of preparing them are described in detail in U.S. Pat. No. 4,963,596. Preferably, the ratio by weight of the solids content of component (C) to the total of active ingredients of component (A) as described above is in the range from 0.1 to 3, more preferably from 0.2 to 2, or still more preferably from 0.20 to 1.6.

A composition prepared by a process as described above constitutes another embodiment of this invention. It is normally preferred that compositions according to the invention as defined above should be substantially free from many ingredients used in compositions for similar purposes in the prior art. Specifically, it is increasingly 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, 0.10, 0.08, 0.04, 0.02, 0.01, or 0.001 percent by weight (hereinafter "w/o") of each of the following constituents: hexavalent chromium; ferricyanide; ferrocyanide; anions containing molybdenum or tungsten; nitrates and other oxidizing agents (the others being measured as their oxidizing stoichiometric equivalent as nitrate); phosphorus and sulfur containing anions that are not oxidizing agents; alkali metal and ammonium cations; and organic compounds with two or more hydroxyl groups per molecule and a molecular weight of less than 300. The preference for minimal amounts of alkali metal and ammonium cations applies only to compositions used for processes according to the invention that include drying into place on the metal surface to be treated without rinsing after contact between the metal surface and the composition containing components (A), (B), and (C) as described above; when a composition according to the invention is contacted with a metal surface and the metal surface is subsequently rinsed with water before being dried, any alkali metal and ammonium ions present are usually removed by the rinsing to a sufficient degree to avoid any substantial diminution of the protective value of subsequently applied organic binder containing protective coatings. Also, the preference for minimization of the amount of hexavalent chromium present is due to the polluting effect of hexavalent chromium, and where there is an absence of legal restraints against pollution and/or sufficiently economical means of disposing of the hexavalent chromium without environmental damage exist, this preference does not apply. In fact, in one specialized embodiment of the invention, as already noted above, hexavalent chromium may advantageously be used to further improve corrosion resistance of the metal surface treated.

Still another embodiment of the invention is a process of treating a metal with a composition prepared as described above. In one embodiment of the invention, it is preferred that the acidic aqueous composition as noted above be applied to the metal surface and dried in place thereon. For example, coating the metal with a liquid film may be accomplished by immersing the surface in a container of the liquid composition, spraying the composition on the surface, coating the surface by passing it between upper and lower rollers with the lower roller immersed in a container of the liquid composition, and the like, or by a mixture of methods. Excessive amounts of the liquid composition that might otherwise remain on the surface prior to drying may be removed before drying by any convenient method, such as drainage under the influence of gravity, squeegees, passing between rolls, and the like.

If the surface to be coated is a continuous flat sheet or coil and precisely controllable coating techniques such as gravure roll coaters are used, a relatively small volume per unit area of a concentrated composition may effectively be used for direct application. On the other hand, if the coating equipment used does not readily permit precise coating at low coating add-on liquid volume levels, it is equally effective to use a more dilute acidic aqueous composition to apply a thicker liquid coating that contains about the same amount of active ingredients. In either case, the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, that is present in the coating that is dried into place on the surface to be treated fall into the range of from 1 to 300, more preferably from 5 to 150, still more preferably from 5 to 100, milligrams per square meter (hereinafter often abbreviated as "mg/m.sup.2 ") of surface area treated.

Drying may be accomplished by any convenient method, of which many are known per se in the art; examples are hot air and infrared radiative drying. Independently, it is preferred that the maximum temperature of the metal reached during drying fall within the range from 30 to 200, more preferably from 30 to 150, still more preferably from 30.degree. to 75.degree. C. Also independently, it is preferred that the drying be completed within a time ranging from 0.5 to 300, more preferably from 2 to 50, still more preferably from 2 to 10, seconds (hereinafter abbreviated "sec") after coating is completed.

According to an alternative embodiment of the invention, the metal to be treated preferably is contacted with a composition prepared as described above at a temperature within the range from 25 to 90, more preferably from 30 to 85, still ore preferably from 30.degree. to 60.degree. C. for a time ranging from 1 to 1800, more preferably from 1 to 300, still more preferably from 3 to 30, sec, and the metal surface thus treated is subsequently rinsed with water in one or more stages before being dried. In this embodiment, at least the final rinse preferably is with deionized, distilled, or otherwise purified water. Also in this embodiment, it is preferred that the maximum temperature of the metal reached during drying fall within the range from 30 to 200, more preferably from 30 to 150, or still more preferably from 30.degree. to 75.degree. C. and that, independently, drying be completed within a time ranging from to 0.5 to 300, more preferably from 2 to 50, still more preferably from 2 to 10 sec after rinsing is completed.

A process according to the invention as generally described in its essential features above may be, and usually preferably is, continued by coating the dried metal surface produced by the treatment as described above with a siccative coating or other protective coating, relatively thick as compared with the coating formed by the earlier stages of a process according to the invention as described above, as known per se in the art. Surfaces thus coated have been found to have excellent resistance to subsequent corrosion, as illustrated in the examples below. Particularly preferred types of protective coatings for use in conjunction with this invention include acrylic and polyester based paints, enamels, lacquers, and the like.

In a process according to the invention that includes other steps after the formation of a treated layer on the surface of a metal as described above and that operates in an environment in which the discharge of hexavalent chromium is either legally restricted or economically handicapped, it is generally 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, 0.10, 0.08, 0.04, 0.02, 0.01, 0.003, 0.001, or 0.0002 w/o of hexavalent chromium. However, in certain specialized instances, hexavalent chromium may impart sufficient additional corrosion protection to the treated metal surfaces to justify the increased cost of using and lawfully disposing of it.

Preferably, the metal surface to be treated according to the invention is first cleaned of any contaminants, particularly organic contaminants and foreign metal fines and/ or inclusions. Such cleaning may be accomplished by methods known to those skilled in the art and adapted to the particular type of metal substrate to be treated. For example, for galvanized steel surfaces, the substrate is most preferably cleaned with a conventional hot alkaline cleaner, then rinsed with hot water, squeegeed, and dried. For aluminum, the surface to be treated most preferably is first contacted with a conventional hot alkaline cleaner, then rinsed in hot water, then, optionally, contacted with a neutralizing acid rinse, before being contacted with an acid aqueous composition as described above.

The practice of this invention may be further appreciated by consideration of the following, non-limiting, working examples, and the benefits of the invention may be further appreciated by reference to the comparison examples.

EXAMPLES

Test Methods and Other General Conditions

Test pieces of Type 3105 aluminum were spray cleaned for 15 seconds at 55.degree. C. with an aqueous cleaner containing 28 g/L of PARCO.RTM. Cleaner 305 (commercially available from the Parker+Amchem Division of Henkel Corp., Madison Heights, Mich., USA). After cleaning, the panels were rinsed with hot water, squeegeed, and dried before roll coating with an acidic aqueous composition as described for the individual examples and comparison examples below.

For the first group of examples and comparison examples below, those according to the dry in place alternative treatment method, the applied liquid composition according to the invention was flash dried in an infrared oven that produces approximately 49.degree. C. peak metal temperature. Samples thus treated were subsequently coated, according to the recommendations of the suppliers, with various commercial paints as specified further below.

T-Bend tests were according to American Society for Testing materials (hereinafter "ASTM") Method D4145-83; Impact tests were according to ASTM Method D2794-84El; Salt Spray tests were according to ASTM Method B-117-90 Standard; Acetic Acid Salt Spray tests were according to ASTM Method B-287-74 Standard; and Humidity tests were according to ASTM D2247-8 Standard. The Boiling water immersion test was performed as follows: A 2T bend and a reverse impact deformation were performed on the treated and painted panel. The panel was then immersed for 10 minutes in boiling water at normal atmospheric pressure, and area of the panel most affected by the T-bend and reverse impact deformations were examined to determine the percent of the paint film originally on these areas that had not been exfoliated. The rating is reported as a number that is one tenth of the percentage of paint not exfoliated. Thus, the best possible rating is 10, indicating no exfoliation; a rating of 5 indicates 50% exfoliation; etc.

Specific Compositions

Example 1

5.6 parts by weight of amorphous fumed silicon dioxide 396.2 parts by weight of deionized water 56.6 parts by weight of aqueous 60 w/o fluotitanic acid 325.4 parts by weight of deionized water 216.2 parts by weight of an aqueous solution containing 10 w/o solids of a water soluble polymer (a Mannich adduct of poly{4-vinylphenol} with N-methylglucamine and formaldehyde) made according to the directions of column 11 lines 39-52 of U.S. Pat. No. 4,963,596.

Example 2

58.8 parts by weight of aqueous 60 w/o fluotitanic acid 646.0 parts by weight of deionized water 5.9 parts by weight of amorphous fumed silicon dioxide 10.5 parts by weight of zirconium hydroxide 278.8 parts by weight of the 10 w/o solution of water soluble polymer as used in Example 1.

Example 3

62.9 parts by weight of aqueous 60 w/o fluotitanic acid 330.5 parts by weight of deionized water 6.2 parts by weight of amorphous fumed silicon dioxide 358.9 parts by weight of deionized water 241.5 parts by weight of the 10 w/o water soluble polymer used in Example 1

Example 4

56.4 parts by weight of aqueous 60 w/o fluotitanic acid 2.1 parts by weight of Aerosil.RTM. R-972 (a surface treated dispersed silica) 56.4 parts by weight of deionized water 667.0 parts by weight of deionized water 218.1 parts by weight of the 10 w/o water soluble polymer used in Example 1

Example 5

58.8 parts by weight of aqueous 60 w/o fluotitanic acid 3.7 parts by weight of amorphous fumed silicon dioxide 10.3 parts by weight of zirconium basic carbonate 647.7 parts by weight of deionized water 279.5 parts by weight of the 10 w/o water soluble polymer used in Example 1

Example 6

52.0 parts by weight of aqueous 60 w/o fluotitanic acid 297.2 parts by weight of deionized water 3.3 parts by weight of amorphous fumed silicon dioxide 9.1 parts by weight of zirconium basic carbonate 273.6 parts by weight of deionized water 364.8 parts by weight of the 10 w/o water soluble polymer used in Example 1

Example 7

11.0 parts by weight of fumed amorphous silicon dioxide 241.0 parts by weight of deionized water 114.2 parts by weight of 60% by weight aqueous fluotitanic acid 33.8 parts by weight of an aqueous composition prepared from the following ingredients: 5.41% by weight of CrO.sub.3 0.59% by weight of pearled corn starch 94% by weight water

For each of Examples 1-6, the ingredients were added in the order indicated to a container provided with stirring. (Glass containers are susceptible to chemical attack by the compositions and generally should not be used, even on a laboratory scale; containers of austenitic stainless steels such as Type 316 and containers made of or fully lined with resistant plastics such as polymers of tetrafluoroethene or chlorotrifluoroethene have proved to be satisfactory.) In each of these Examples except Example 4, after the addition of the silica component and before the addition of the subsequently listed components, the mixture was heated to a temperature in the range from 38.degree.-43.degree. C. and maintained within that range of temperatures for a time of 20-30 minutes. Then the mixture was cooled to a temperature below 30.degree. C., and the remaining ingredients were stirred in without additional heating, until a clear solution was obtained after each addition.

For Example 4, the SiO.sub.2 used was surface modified with a silane, and because of its hydrophobic nature, the mixture containing this form of silica was heated for 1.5 hours at 70.degree. C. to achieve transparency. The remaining steps of the process were the same as for Example 1.

For Example 7, the first three ingredients listed were mixed together and maintained at 40.degree..+-.5.degree. C. for 10 minutes with stirring and then cooled. In a separate container, the CrO.sub.3 was dissolved in about fifteen times its own weight of water, and to this solution was added a slurry of the corn starch in twenty-four times its own weight of water. The mixture was then maintained for 90 minutes with gentle stirring at 88.degree..+-.6.degree. C. to reduce part of the hexavalent chromium content to trivalent chromium. Finally, this mixture was cooled with stirring and then added to the previously prepared heated mixture of fluotitanic acid, silicon dioxide, and water. This composition is used in the manner known in the art for compositions containing hexavalent and trivalent chromium and dispersed silica, but it is much more stable to storage without phase separation.

Comparative Example 1

18.9 parts by weight of aqueous 60 w/o fluotitanic acid 363.6 parts by weight of the 10 w/o water soluble polymer used in Example 1 617.5 parts by weight of deionized water

Comparative Example 2

18.9 parts by weight of aqueous 60 w/o fluotitanic acid 71.8 parts by weight of the 10 w/o water soluble polymer used in Example 1 909.3 parts by weight of deionized water

For Comparative Examples 1 and 2 the components were added together with agitation in the order indicated, with no heating before use in treating metal surfaces.

Add-on mass levels, specific paints used, and test results with some of the compositions described above are shown in Tables 1-5 below.

TABLE 1______________________________________Panels Painted with PPG Duracron.TM. 1000 WhiteSingle Coat Acrylic PaintBoiling Water HAc SaltTreat- 2T Coating Spray 504 Humidityment Bend Impact Weight Hours 1008 Hrs.______________________________________Example 1 9 10 65 mg/m.sup.2 e 0-1.sup.s Vf9 as Ti s 0-1.sup.sExample 1 9 10 43 mg/m.sup.2 e 0-1.sup.s Vf9 as Ti s 0-1.sup.sCompara- 5 7 39 mg/m.sup.2 e 0-1.sup.s D9tive as Ti s 0-2.sup.sExample 1Compara- 0 0 27 mg/m.sup.2 e 0-1.sup.s D9tive as Ti s 0-2.sup.sExample 1Compara- 7 8 65 mg/m.sup.2 e 0-1.sup.s Vf9tive as Ti s 0-1.sup.sExample 2Compara- 4 6 29 mg/m.sup.2 e 0-1.sup.s Fm9tive as Ti s 0-1.sup.sExample 2______________________________________ TABLE 2______________________________________Panels Painted with Lilly.TM. Colonial White Single CoatPolyesterBoiling Salt Humid-Water HAc Salt Spray ityTreat- 2T Im- Coating Spray 504 1008 1008ment Bend pact Weight Hours Hours Hrs.______________________________________Example 5 8 65 mg/m.sup.2 e N e N Vf.sup.94 as Ti s N s NExample 10 10 22 mg/m.sup.2 e N e N Vf.sup.95 as Ti s N s NExample 10 10 54 mg/m.sup.2 e N e N Vf.sup.95 s N s NExample 10 10 22 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.96 s N s NExample 10 10 54 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.96 s N s N______________________________________ TABLE 3______________________________________Panels Painted with Lilly.TM. Black Single Coat PolyesterBoiling Salt Humid-Water HAc Salt Spray ityTreat- 2T Im- Coating Spray 504 1008 1008ment Bend pact Weight Hours Hours Hrs.______________________________________Example 10 10 54 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.92 as Ti s N s NExample 10 10 64 mg/m.sup.2 e 0-2.sup.s e 0-1.sup.s Vf.sup.93 as Ti s 0-2.sup.s s N______________________________________ TABLE 4______________________________________Panels Painted with Valspar/Desoto.TM. White Single CoatPolyesterBoiling Salt Humid-Water HAc Salt Spray ityTreat- 2T Im- Coating Spray 1008 1008 1008ment Bend pact Weight Hours Hours Hrs.______________________________________Example 10 10 39 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.92 as Ti s 0-1.sup.2 s NExample 10 10 48 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.92 as Ti s 0-1.sup.s s NExample 10 10 70 mg/m.sup.2 e 0-2.sup.s e N Vf.sup.92 as Ti s 0-1.sup.s s NExample 10 10 87 mg/m.sup.2 e N e 0-1.sup.s Vf.sup.92 as Ti s 0-1.sup.s s NExample 10 10 29 mg/m.sup.2 e 0-2.sup.s e N Vf.sup.93 as Ti s 0-1.sup.s s NExample 10 10 42 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.93 as Ti s 0-1.sup.s s NExample 10 10 57 mg/m.sup.2 e 0-1 e N Vf.sup.93 as Ti s 0-1.sup.s s NExample 10 10 82 mg/m.sup.2 e 0-2.sup.s e 0-1.sup.s Vf.sup.93 as Ti s 0-2.sup.s s NExample 7 10 65 mg/m.sup.2 e 0-1.sup.s e N Vf.sup.94 as Ti s 0-1.sup.s s N______________________________________ TABLE 5______________________________________Panels Painted with Valspar.TM. Colonial White Single CoatPolyesterBoiling Salt Humid-Water HAc Salt Spray ityTreat- 2T Im- Coating Spray 504 1008 1008ment Bend pact Weight Hours Hours Hrs.______________________________________Example 10 10 54 mg/m.sup.2 e N e N Fm.sup.92 as Ti s N s NExample 10 10 64 mg/m.sup.2 e 0-1.sup.s e 0-1.sup.s Fm.sup.93 as Ti s N s 0-1.sup.s______________________________________

The storage stability of the compositions according to all of the examples above except Example 2 was so good that no phase separation could be observed after at least 1500 hours of storage. For Example 2, some settling of a slight amount of apparent solid phase was observable after 150 hours.

To obtain the results reported in the following tables, an alternative process of treating the metal surfaces according to the invention and a different aluminum alloy were used. Specifically, test pieces of Type 5352 or 5182 aluminum were spray cleaned for 10 seconds at 55.degree. C. with an aqueous cleaner containing 24 g/L of PARCO.RTM. cleaner 305 (commercially available from the Parker+Amchem Division of Henkel Corp., Madison Heights, Mich., USA). After cleaning, the panels were rinsed with hot water; then they were sprayed with the respective treatment solutions according to the invention, which were the same as those already described above with the same Example Number except that they were further diluted with water to the concentration shown in the tables below, for 5 seconds; and then were rinsed in water and dried, prior to painting.

The "OT Bend" column in the following tables reports the result of a test procedure as follows:

1. Perform a 0-T bend in accordance with ASTM Method D4145-83. Firmly apply one piece of #610 Scotch.RTM. tape to the area of the test panel with the 0-T bend and to the adjacent flat area. 3. Slowly pull the tape off from the bend and the adjacent flat area. 4. Repeat steps 2 and 3, using a fresh piece of tape for each repetition, until no additional paint is removed by the tape. 5. Report the maximum distance from the 0-T bend into the flat area from which paint removal is observed according to the scale below: ______________________________________Paint loss in mm Rating______________________________________0 5.00.8 4.51.6 4.02.4 3.53.2 3.04.0 2.54.8 2.05.6 1.56.4 1.07.2 0.5>7.2 0______________________________________

The "Ninety Minute Steam Exposure" columns of the tables below report the results of tests performed as follows:

1. Expose the painted samples to steam at a temperature of 120.degree. C. steam for 90 minutes in a pressure cooker or autoclave. 2. Crosshatch the painted sample--two perpendicular cuts; a Gardner crosshatch tool with 11 knife edges spaced 1.5 mm apart was used. 3. Firmly apply #610 Scotch.RTM. tape to the crosshatched area and remove tape. 4. Examine the crosshatched area for paint not removed by the tape and report a number representing one-tenth of the percentage of paint remaining. 5. Using a microscope at 10-80 times magnification, visually observe crosshatched area for blistering, and rate size and density of blisters.

The "15 Minute Boiling DOWFAX.TM. 2Al Immersion" columns of the tables below report the results of tests performed after treatment as follows:

1. Prepare solution of 1% by volume of DOWFAX.TM. 2Al in deionized water and bring to boil. 2. Immerse painted test panels in the boiling solution prepared in step 1 and keep there for 15 minutes; then remove panels, rinse with water, and dry.

DOWFAX.TM. 2Al is commercially available from Dow Chemical and is described by the supplier as 45% active sodium dodecyl diphenyloxide disulfonate. The "Cross Hatch" test after this treatment was made in the same way as described above for steps 2-4 after "Ninety Minute Steam Exposure". The "Reverse Impact" test was made as described in ASTM D2794-84El (for 20 inch pounds impact), then proceeding in the same way as described above for steps 3-4 after "Ninety Minute Steam Exposure". The "Feathering" test was performed as follows: Using a utility knife, scribe a slightly curved "V" on the back side of the test panel. Using scissors, cut up about 12 millimeters from the bottom along the scribe. Bend the inside of the V away from side for testing. Place sample in a vise and, using pliers, pull from the folded section with a slow continuous motion. Ignore the part of the panel between the top edges nearest to the vertex and a line parallel to the top edge but 19 mm away from it. On the remainder of the panel, measure to edge of feathering in millimeters. Record the largest value observed.

The results of tests according to these procedures are shown in Tables 6-8 below.

TABLE 6______________________________________5182 alloy panels Painted with Valspar.TM. S-9835002Paint______________________________________ 15 Minute Boiling DOWFAX.TM.Inven- 2A1 Immersiontion Re-Compo- Concen- Coating Cross verse Feather-sition tration pH Weight Hatch Impact ing______________________________________Example 1% by 2.9 7.9 mg/m.sup.2 10 10 0.35 mm1 weight as Ti______________________________________ TABLE 7______________________________________5352 Alloy Panels Painted with Valspar.TM. S-9009-139PaintInven- Ninety Minutetion Steam ExposureCompo- Concen- Coating OT Cross Blist-sition tration pH Weight Bend Hatch ering______________________________________Example 1% 2.7 4.0 5 10 Very1 mg/m.sup.2 few, as ti small- mediumExample 1% 3.2 11.4 5 10 few,1 mg/m.sup.2 small as TiExample 3% 2.5 2.3 5 10 very1 mg/m.sup.2 few, as Ti very smallClean N/A 1.5 10 few,only medium(Com-pari-son)______________________________________ TABLE 8______________________________________5352 Alloy Panels Painted with Valspar.TM. S-9009-154PaintInven- Ninety Minutetion Steam ExposureCompo- Concen- Coating OT Cross Blist-sition tration pH Weight Bend Hatch ering______________________________________Example 1% 2.9 4.2 5 9-10 Very1 mg/m.sup.2 few, as Ti smallExample 3% 2.7 2.6 5 9-10 very1 mg/m.sup.2 few, as Ti very small______________________________________

Claims

1. A process comprising steps of:

(I) providing a mixture consisting essentially of water and:

(A) a dissolved component selected from the group consisting of H.sub.2l TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 HfF.sub.6, H.sub.2 SiF.sub.6, H.sub.2 GeF.sub.6, H.sub.2 SnF.sub.6, HBF.sub.4, and mixtures thereof and

(B) a dissolved, dispersed, or both dissolved and dispersed component selected from the group consisting of Ti, Zr, Hf, Al, Si, Ge, Sn, and B, the oxides, hydroxides, and carbonates of Ti, Zr, Hf, Al, Si, Ge, Sn, and B, and mixtures of any two or more of these elements, oxides, hydroxides, and carbonates;

(II) agitating the mixture provided in step (I) for at least a sufficient time at a sufficient temperature that the mixture is free from any visually observable evidence of phase separation and is sufficiently stable that it would remain free from any visually observable evidence of phase separation during storage at temperature in the range from 20.degree. to 25.degree. C. for a period of at least 100 hours;

(III) mixing with the agitated mixture from the end of step (II) a component (C) selected from the group consisting of (1) water soluble and water dispersible polymers and copolymers of x-(N--R.sup.1 --N--R.sup.2 -aminomethyl)-4-hydroxy-styrenes, where x=2, 3, 5, or 6; R.sup.1 represents an alkyl group containing from 1 to 4 carbon atoms; and R.sup.2 represents a substituent group conforming to the general formula H(CHOH).sub.n --, where n is an integer from 3 to 8 and mixtures of any two or more therof; and (2) dissolved hexavalent chromium to form a mixture that is sufficiently stable that it would remain free from any visually observable evidence of phase separation during storage at temperature in the range from 20.degree. to 25.degree. C. for a period of at least 100 hours.

2. An aqueous liquid mixture made by a process according to claim 1.

3. A process according to claim 1 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 1 to 300 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 25.degree. to 90.degree. C. for a time in the range from 1 to 1800 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface.

4. A process according to claim 1 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 100 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing, within a time in the range from 2 to 50 seconds after coating is completed; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 60.degree. C. for a time in the range from 3 to 30 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface within a time from 2 to 50 seconds after rinsing is completed.

5. A process according to claim 1, wherein (i) the mixture provided in step (I) contains a total amount in the range from 0.01 to 7.0 M of material selected from the group consisting of H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 HfF.sub.6, H.sub.2 SiF.sub.6, HBF.sub.4 and mixtures thereof and has a ratio of moles of component (A) to equivalents of component (B) in the range from 1:1 to 50:1; (ii) during step (II) the mixture is maintained at a temperature in the range from 25.degree. to 100.degree. C. for a time in the range from 3 to 480 minutes; and (iii) component (C) comprises a total amount of water soluble and water dispersible polymers and copolymers of x-(N--R.sup.1 --N--R.sup.2 -aminomethyl)-4-hydroxy-styrenes, where x=2, 3, 5, or 6, R.sup.1 represents an alkyl group containing from 1 to 4 carbon atoms, and R.sup.2 represents a substituent group conforming to the general formula H(CHOH).sub.n --, where n is an integer from 3 to 8, such that the ratio by weight of said water soluble and water dispersible polymers and copolymers to the total weight of component (A) is in the range from 0.1:1 to 3:1.

6. An aqueous liquid mixture made by a process according to claim 5.

7. A process according to claim 5 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 1 to 300 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 25.degree. to 90.degree. C. for a time in the range from 1 to 1800 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface.

8. A process according to claim 5 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 100 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing, within a time in the range from 2 to 50 seconds after coating is completed; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30 to 60 C for a time in the range from 3 to 30 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface within a time from 2 to 50 seconds after rinsing is completed.

9. A process according to claim 1, wherein (i) the mixture provided in step (I) contains a total amount in the range from 0.1 to 6.0 M of material selected from the group consisting of H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub. SiF.sub.6, and mixtures thereof; has a ratio of moles of component (A) to total equivalents of oxides, hydroxides, and carbonates of silicon, zirconium, and aluminum in the range from 1.5:1.0 to 20:1; and has a pH value in the range from 0 to 4; (ii) during step (II) the mixture is maintained at a temperature in the range from 30.degree. to 80.degree. C. for a time in the range from 5 to 90 minutes; and (iii) component (C) comprises a total amount of water soluble and water dispersible polymers and copolymers of x-(N-R.sup.1 -N-R.sup.2 -aminomethyl)-4-hydroxy-styrenes, where x=2, 3, 5, or 6, R1 represents an alkyl group containing from 1 to 4 carbon atoms, and R.sup.2 represents a substituent group conforming to the general formula H(CHOH).sub.n --, where is an integer from 3 to 8, such that the ratio by weight of said water soluble and water dispersible polymers and copolymers to the total weight of component (A) is in the range from 0.2:1 to 2:1.

10. An aqueous liquid mixture made by a process according to claim 9.

11. A process according to claim 9 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 1 to 300 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 25.degree. to 90.degree. C. for a time in the range from 1 to 1800 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface.

12. A process according to claim 9 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 100 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing, within a time in the range from 2 to 50 seconds after coating is completed; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 60.degree. C. for a time in the range from 3 to 30 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface within a time from 2 to 50 seconds after rinsing is completed.

13. A process according to claim 1, wherein (i) the mixture provided in step (I) contains a total amount in the range from 0.1 to 6.0 M of material selected from the group consisting of H.sub.2 TiF.sub.6, H.sub.2 ZrF.sub.6, H.sub.2 SiF.sub.6, and mixtures thereof; has a ratio of moles of component (A) to total equivalents of oxides, hydroxides, and carbonates of silicon, zirconium, and aluminum in the range from 1.5:1.0 to 5:1; and has a pH value in the range from 0 to 2; (ii) during step (II) the mixture is maintained at a temperature in the range from 30.degree. to 80.degree. C. for a time in the range from 10 to 30 minutes; and (iii) component (C) comprises a total amount of water soluble and water dispersible polymers and copolymers of x-(N--R.sup.1 --N--R.sup.2 --aminomethyl)-4-hydroxy-styrenes, where x=2, 3, 5, or 6, R.sup.1 represents an alkyl group containing from 1 to 4 carbon atoms, and R.sup.2 represents a substituent group conforming to the general formula H(CHOH).sub.n -, where n is an integer from 3 to 8, such that the ratio by weight of said water soluble and water dispersible polymers and copolymers to the total weight of component (A) is in the range from 0.20:1 to 1.6:1.

14. An aqueous liquid mixture made by a process according to claim 13.

15. A process according to claim 13 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 150 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 85.degree. C. for a time in the range from 1 to 300 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface.

16. A process according to claim 13 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 100 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing, within a time in the range from 2 to 50 seconds after coating is completed; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 60.degree. C. for a time in the range from 3 to 30 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface within a time from 2 to 10 seconds after rinsing is completed.

17. A process according to claim 1, wherein (i) the mixture provided in step (I) contains a total amount in the range from 0.1 to 6.0 M of H.sub.2 TiF.sub.6 ; has a ratio of moles of H.sub.2 TiF.sub.6 to total equivalents of silicon dioxide in the range from 1.5:1.0 to 5:1; and has a pH value in the range from 0.0 to 1.0; (ii) during step (II) the mixture is maintained at a temperature in the range from 30.degree. to 80.degree. C. for a time in the range from 10 to 30 minutes; and (iii) component (C) comprises a total amount of water soluble and water dispersible polymers and copolymers of x-{[(N-methylamino)glucamino]methyl}-4-hydroxy-styrenes, where x=2, 3, 5, or 6, such that the ratio by weight of said water soluble and water dispersible polymers and copolymers to the total weight of H.sub.2 TiF.sub.6 is in the range from 0.20:1 to 1.6:1.

18. An aqueous liquid mixture made by a process according to claim 17.

19. A process according to claim 17 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 150 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 85.degree. C. for a time in the range from 1 to 300 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface.

20. A process according to claim 17 comprising an additional step (IV) selected from the group consisting of:

(IV.1) coating a metal surface with a layer of the liquid composition from the end of step (III), said layer having a thickness such that it contains from 5 to 100 mg/m.sup.2 of the metal surface of the total amount of elements selected from the group consisting of Ti, Zr, B, Si, Ge, Sn, and drying said layer of the liquid composition from the end of step (III) into place on said metal surface, without intermediate rinsing, within a time in the range from 2 to 10 seconds after coating is completed, while bringing the maximum metal temperature during drying to a value between 30.degree. and 75.degree. C.; and

(IV.2) contacting a metal surface with the liquid composition from the end of step (III) at a temperature in the range from 30.degree. to 60.degree. C. for a time in the range from 3 to 30 seconds, removing the metal surface from contact with said liquid composition from the end of step (III), rinsing said metal surface with water, and drying the rinsed metal surface within a time from 2 to 10 seconds after rinsing is completed, while bringing the maximum metal temperature during drying to a value between 30.degree. and 75.degree. C.