Multilayer coatings for metal substrates

Abstract

A multilayered coating (10) that is applied to a metal substrate (12). The coating comprises a protective zone of an insoluble crystalline phosphate formed by reaction of the substrate (12) with zinc phosphate. A film (16) of a polymer resin is deposited on the insoluble crystalline phosphate zone (14). In one embodiment, the multilayered coating (10) includes a coat of paint (18) that is applied to the polymer resin (16). A process for applying the multilayered coating to the metal substrate includes the steps of: applying a zinc phosphating solution to at least a portion of the substrate, which converts the surface to a zone of an insoluble crystalline phosphate; rinsing the zone; and autodepositing a film of a polymer resin thereupon.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. provisional application Serial No. 60/296,326 filed Jun. 5, 2001.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to multilayer coatings that are applied to metal substrates, such as cold-rolled steel, electrogalvanized steel, or aluminum. The coatings include a layer of zinc phosphate. An epoxy paint is applied, preferably by autodeposition techniques.

[0004] 2. Background Art

[0005] During an era in which the consumer tends to purchase a product based upon such factors as its appearance and price, the manufacturer is faced with seemingly endless opportunities and challenges regarding surface finish. This is especially true in the automobile industry. For example, if a manufacturing step can be eliminated, such as applying a primer before a top coat, other things being equal, manufacturing economies are realized. It would, of course, be desirable to eliminate such a step while preserving an attractive, lustrous appearance to the paint system which is applied to the product.

[0006] Conventionally, a paint system is created by preparing the substrate and then applying multilayered coatings by various methods. In the art and science of pretreatment and paint systems, it is known to expose the substrate to zinc phosphating solution and then to apply a paint film. To that end, the following United States patents are relevant and are incorporated herein by reference: Hall U.S. Pat. Nos. 5,352,726; Hall et al. 5,912,297; Honda et al. 6,033,492; Mueller et al. 6,096,806; Ahmed 6,143,365; and Blum et al. 6,165,561.

[0007] Current automobile body assembly trends indicate that pretreatment and paint suppliers must develop new painting concepts with fewer steps and higher performance. The conventional automotive paint pretreatment/paint processes include the following initial nine (9) steps: 1 (1) Clean; (2) Rinse; (3) Condition; (4) Phosphate; (5) Rinse; (6) Post-rinse; (7) Deionized water rinse; (8) Cationic electrocoat prime; and (9) Cure.

[0008] It would be desirable to shorten the pretreatment/paint process by combining certain steps, if possible, by using a high performance product to replace current post-rinse technology, which would reduce or eliminate the use of electrocoat paint.

[0009] It would also be beneficial to develop a high performance product to replace both the post-rinse and electrocoat paint steps, thus providing both a streamlined paint process and a high performance paint finish. “Autodeposition” or “autodepositing” compositions are denoted in this specification as dispersions, emulsions, suspensions, baths, solutions, or a like term. Autodeposition is a water-borne, organic coating process which uses chemical reactions instead of electrical energy to achieve the deposition of a high quality organic finish. Autodeposition does not require the aid of external electrical current to deposit resin particles on the metal surface. Such coatings have a relatively high degree of corrosion resistance. When the autodepositing composition contains a suitable pigment, such coatings are particularly suited for providing a uniform colored appearance.

[0010] The coating formed while a metal substrate is immersed in an autodeposition bath is wet and fairly weak, although sufficiently strong to maintain itself against gravity and moderate spraying forces. In this state, the coating is described as “uncured.” To make an autodeposition-coated object suitable for normal practical use, the uncured coating is dried, usually with the aid of heat. The coating is then described as “cured.”

[0011] One defining characteristic of autodepositing water-based coating compositions is that by contacting a suitable metal material having a clean surface with the coating composition, a resin coating film, which increases in thickness or weight as immersion time increases, forms spontaneously as a result of chemical reaction between the metal and the coating composition. Without being bound by any particular theory, metal ions dissolved from the metal surface are believed to interact with the resin particles. Thus, a resin coating film can be beneficially formed on the metal surface without the need for external electromotive force, as is required in electrodeposition.

[0012] However, in some cases, the corrosion resistance and adhesion of an autodeposited resin coating film is not entirely satisfactory. Various means have been disclosed for improving these properties. Such means include chemical treatments of wet autodeposited coating films before they are dried. Such chemical treatments are known by various terms in the art: the most common such name is probably “final rinse,” which is well-established but often a misnomer, because there may be other subsequent water rinses. Other terms are “after-treatment,” “post-treatment,” “reaction rinse,” “chemical rinse,” and “modifying rinse.”

[0013] Electrodeposition involves precipitation of material at an electrode as a result of the passage of an electric current through a solution or suspension of the material. HAWLEY'S CONDENSED CHEMICAL DICTIONARY, p. 455, 11th ED. (1987). The electrode is often in the shape of the desired substrate. An advantage of electrodeposition is its ability to coat complex shapes with small and irregular cavities with some control over thickness of the deposited coating. Some variations occur, however, as a result of poor throwing power. The electrodeposition can produce adherent films, but requires that the surface to be coated be connected to a source of direct current electricity for coating to occur.

[0014] Electrodeposition by electrophoresis involves the migration of suspended or colloidal particles in a liquid such as rubber or latex due to the effect of a potential difference across immersed electrodes. HAWLEY'S CONDENSED CHEMICAL DICTIONARY, p. 457, 11TH ED. (1987). The migration is toward the electrodes which are charged opposite to that of the particles. Thus solids, being negatively charged, migrate to the anode. Basic dyes, hydroxide solutions, and colloids which have adsorbed positive ions migrate to the cathode. Migrating particles lose their charge at the electrode and generally agglomerate around it.

[0015] 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, however. Also, throughout the description, unless expressly stated to the contrary: percent, “parts of,” and ratio values are by weight or mass; the term “polymer” includes “oligomer,” “copolymer,” “terpolymer” and the like; the description of a group or class of materials as suitable or preferred for a given purpose in connection with the invention implies that mixtures of any two or more of the members or of the group or class are equally suitable or preferred; the description of constituents in chemical terms refers to the constituents at the time of addition to any combination specified in the description or are generation in situ within the composition by chemical reaction(s) noted in the specification between one or more newly added constituents and one or more constituents already present in the composition when the other constituents are added, and does not necessarily preclude unspecified chemical interactions among the constituents of a mixture once mixed; specification of constituents in ionic form additionally implies the presence of sufficient counterions to produce electrical neutrality for the composition as a whole and for any substance added to the composition; any counterions thus implicitly specified preferably are selected from among other constituents explicitly specified in ionic form, to the extent possible; otherwise such counterions may be freely selected, except for avoiding counterions that act adversely to an object of the invention; the word “mole” means “gram mole,” and the word itself and all of its grammatical variations may be used for any chemical species defined by all of the types and numbers of atoms present in it, irrespective of whether the species is ionic, neutral, unstable, hypothetical, or in fact a stable neutral substance with well-defined molecules; and the terms “solution,” “soluble,” “homogeneous,” and the like are to be understood as including not only true equilibrium solutions or homogeneity but also dispersions that show no visually detectable tendency toward phase separation over a period of observation of at least 100, or preferably at least 1000, hours during which the material is mechanically undisturbed and the temperature of the material is maintained within the range of 18-25° C.

[0016] An additional inquiry made before converting the parent provisional to the present non-provisional case revealed the following references as relevant art: U.S. Pat. Nos. 3,960,610; 6,165,561; commonly owned Publication No. WO 00/71625; and commonly owned pending U.S. Serial No. 60,252,799 that was filed on Nov. 22, 2000; and Ser. No. 09/990,066 filed on Nov. 21, 2001 (to be published as a PCT Application in May 2002). These references teach preferred methods of post-rinsing and autodeposited epoxy coating prior to curing. The disclosures of each of the references specified in this paragraph are incorporated herein by reference.

SUMMARY OF THE INVENTION

[0017] The present invention involves a pretreatment and paint system that includes a zinc phosphate layer 14 and an autodeposited epoxy film 16. Optionally, a paint 18 can be applied by an electrocoating process that provides corrosion protection to such metallic substrates 12 as a cold-rolled steel, an electrogalvanized steel, and aluminum. When the electrodeposited coating 18 is used, it is applied over the uncured autodeposited epoxy film 16.

[0018] Thus, the invention relates to a multilayered coating composition 10 that is applied to a metal substrate 12, and to a process by which the application is made. The multilayered coating comprises a layer of zinc phosphate 14 which converts the surface of the substrate 12 to an integral, protective zone of an insoluble crystalline phosphate, the zone serving as a base for paint to be applied. The film of an epoxy resin 16 is autodeposited on the layer of zinc phosphate 14.

[0019] The process for applying the multilayered coating to the metal substrate 12 comprises the steps of:

[0020] 1. applying a zinc phosphating solution 14 to the substrate 12 to form a phosphate-treated substrate;

[0021] 2. rinsing the phosphate-treated substrate; and

[0022] 3. autodepositing a film of a polymer resin 16 on the rinsed phosphate-treated substrate.

[0023] Optionally, the following steps may also be taken:

[0024] 4. post-rinsing the film of a polymer resin 16; and

[0025] 5. electrodepositing a coat of paint 18 upon the film of post-rinsed polymer resin 16.

[0026] There are at least two advantages to following the teachings of the present invention. First, the invention provides for the coating of interior sections of complex shapes which are not coated in an electrocoating bath due to poor throwing power. Second, the use of an autodeposited epoxy coating and a zinc phosphate results in reducing or eliminating the need for an electro coat primer in many paint systems, including those used in the automotive industries.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 is a schematic, cross-sectional view of a substrate to which a multilayered coating according to the embodiment of the present invention is applied;

[0028] FIGS. 2(a-d) are process flow diagrams which compare the conventional with the inventive steps and their alternatives disclosed herein; and

[0029] FIG. 3 is a process flow diagram which depicts the main steps and their alternatives followed in practicing the disclosed invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0030] Turning first to FIG. 1, there is depicted a multilayered coating 10 that is applied to a metal substrate 12. The coating includes a layer of zinc phosphate 14 that converts the surface of the substrate 12 to an integral, mildly protective zone of an insoluble crystalline phosphate. The layer 14 serves as a base for a film of an epoxy resin 16 or paint 18 to be applied. The film of an epoxy resin 16 is autodeposited on the layer of the zinc phosphate 14.

[0031] FIG. 2 depicts the main method and alternative steps to be followed in practicing a process for applying the multilayered coating 10 to the metal substrate 12. The process comprises the steps of:

[0032] 1. applying zinc phosphate 14 to the substrate for converting the surface of the substrate 12 to an integral, protective zone of an insoluble crystalline phosphate;

[0033] 2. rinsing the phosphate-treated substrate; and

[0034] 3. autodepositing a film of a polymer resin 16 on the rinsed phosphate-treated substrate.

[0035] Optionally, where the film of a polymer resin 16 fails to provide a desired finish, the following steps can additionally be taken:

[0036] 4. post-rinsing the film 16; and

[0037] 5. electrodepositing a coat 18 of paint upon the film 16.

[0038] Optionally, the post-rinse step may be akin to that disclosed in commonly owned U.S. Pat. No. 6,143,365, which is incorporated herein by reference.

[0039] The preferred autodepositing compositions for use in the present invention include those where the epoxy or resin is in the form of a latex, most preferably with an aqueous dispersed resin content of less then 15% by weight. The autodeposition coatings that are based on epoxy resins are disclosed in Published PCT Application No. WO 00/071337 (based on U.S. Ser. No. 09/578,935 filed May 25, 2000) and U.S. Pat. No. 6,096,806, each being incorporated herein by reference. Examples of alternative compositions include Autophoretic® 900 Series, Autodepositing compositions based on epoxy resins, and Autophoretic® 800 Series autodepositing compositions based on polyvinylidene chloride resins and 700 Series autodepositing compositions based on acrylic resins, each composition being made by Henkel Surface Technologies. Such compositions preferably contain hydrofluoric acid and hydrogen peroxide or iron (III) fluoride as the oxidizing agent.

EXAMPLES

[0040] The inventors have evaluated the use of an autodeposited epoxy film 16 prior to coating with and without an epoxy paint 18 by electrodeposition. Panels made of different metals were treated with various phosphate pretreatments, followed by an autodeposited polymer film.

[0041] Materials

[0042] Cold-rolled steel (CRS), electro-galvanized steel (EG), and aluminum 6111 T4 alloy (AL) were purchased from ACT Laboratories, Hillsdale, Mich. Parco® Cleaner (PCL) 1523, Fixodine (Fix) Z-8, Bonderite (B) 958, Parcolene (PLN) 90 Autophoretic® Coating Chemical 901 and Autophoretic® Starter 300 were taken from laboratory stock. Electrodeposition primer ED-5050B was obtained from PPG. A second epoxy dispersion was prepared according to Formula A: 2 TABLE 1 Epoxy Dispersions Formula A Part Ingredient by Weight Description Manufacturer PB-8990 2100.9 Epoxy resin Henkel Surface Technologies Vestagon B1530  254.3 Blocked Huls isocyanate crosslinker Texanol  101.2 Coalescesing Eastman solvent Methylisobutylketone 1277.4 Dispersing solvent Rhodapex CO 436  76.6 Surfactant Rhone Poulenc Deionized Water 5189.6 Solvent Total 9000.0 17.8% solids

[0043] Methylisobutylketone and water were removed from both PTD-3002-C and BHG2824-125-1 by azeotropic distillation at 190-212° F. until the final epoxy dispersion was 25-27% solids.

[0044] Typical autodepositing Autophoretic® Coatings Chemicals (ACC) baths were prepared according to the following formulas: 3 TABLE 2 Epoxy Autodepositing Baths Ingredient Coating Bath 123-1 Coating Back 127-1 DI water 3000 3000 ACC 901 3000   0 Formula A   0 3000 ACC Starter 300  295  295 % solids  12.1  12.0 Fe titration 22-24 22-24 Redox Potential  475 mv  390 mv Fluoride level  170 &mgr;a  160 &mgr;a (Lineguard 101 meter)

[0045] Procedures

[0046] Epoxy ACC baths 123-1 and 127-1 were used according to the Technical Process Bulletin for Autophoretic® 901 Coating Chemical, which is incorporated by reference herein. The redox condition of the epoxy ACC bath was monitored with a platinum oxidation reduction potential electrode. The fluoride level in the epoxy bath was monitored with a Lineguard 101 meter. Surface tension was measured using the Kruss K-12 Tensiometer in the Wilhelmy Plate mode.

[0047] Results and Discussion

[0048] Coating Processes

[0049] Three coating sequences were tested for effectiveness as pretreatment and primer systems for CRS, EG and AL. All panels were coated using one of the following procedures: 4 Process A (FIG. 2a: Standard Zinc Phosphating Process Plus ED Primer) Step No. Task Description 1 Clean Parco ® Cleaner 1523, 5-7 pts, 120° F., 90 sec 2 Rinse Warm water rinse, 120° F., 30 sec 3 Condition Fixodine Z8, 1.5 g/l, pH = 8.8-9.0, 100° F., 30 sec 4 Phosphate Bonderite 958, FA = 0.6, TA = 22.6, F− = 120 &mgr;a, 120° F., 120 sec 5 Rinse Cold water rinse, 65° F., 30 sec 6 Post-rinse Parcolene 90, pH = 5.6, concentration = 15 ml, 30 sec 7 Deionized post- Deionized water rinse, 30 sec rinse 8 Electrocoat paint ED-5050B cationic electrocoat primer 9 Cure

[0050] 5 Process B (FIG. 2b: Invention) Step No. Task Description 1 Clean Parco ® Cleaner 1523, 5-7 pts, 120° F., 90 sec 2 Rinse Warm water rinse, 120° F., 30 sec 3 Condition Fixodine Z8, 1.5 g/l, pH = 8.8-9.0, 100° F., 30 sec 4 Phosphate Bonderite 958, FA = 0.6, TA = 22.6, F− = 120 ma, 120° F., 120 sec 5 Rinse Deionized Water Rinse, 65° F., 30 sec 6 Autodeposit ACC coating bath 123-1 or 127-1 7 Post-rinse Deionized water rinse, 65° F., 30 sec 8 Electrocoat paint ED-5050B cationic electrocoat primer 9 Cure

[0051] 6 Process C (FIG. 2c: Invention) Step No. Task Description 1 Clean Parco ® Cleaner 1523, 5-7 pts, 120° F., 90 sec 2 Rinse Warm water rinse, 120° F., 30 sec 3 Condition Fixodine Z8, 1.5 g/l, pH = 8.8-9.0, 100° F., 30 sec 4 Phosphate Bonderite 958, FA = 0.6, TA = 22.6, F− = 120 ma, 120° F., 120 sec 5 Rinse Deionized water rinse, 65° F., 30 sec 6 Autodeposit ACC coating bath 123-1 or 127-1 7 Post-rinse 8 Cure

[0052] 7 Process D Step No. Task Description 1 Clean Parco ® Cleaner 1523, 5-7 pts, 120° F., 90 sec 2 Rinse Warm water rinse, 120° F., 30 sec 3 Autodeposit ACC coating bath 123-1 or 127-1 4 Post-rinse 5 Cure

[0053] Process A (FIG. 2a) is the standard nine-stage zinc phosphating system plus electrocoat primer. Process B (FIG. 2b) utilizes the first five stages of Process A with autodepositing coating chemical (ACC) formula 127-1 replacing the post-rinse stage (Process A, step 6), followed by rinsing and electrocoat paint (Process B, steps 7, 8) for a total of nine stages. Process C (FIG. 2c) also utilizes the first five stages of Process A followed by 123-1 (Process C, step 6) without the electrocoat paint step 8 (Processes A,B). Process D eliminates steps 3-5 (notably, the phosphating step) of Process C. Appendix A summarizes various details of the pretreatment-autodeposition-electrocoating process.

[0054] The coating experiments showed that all three substrates (CRS, EG and Al) could be coated using an epoxy coating. In addition, the epoxy coating could be deposited over zinc phosphate on CRS, EG and AL under similar conditions. In a multi-metal process such as automotive body assembly, it is thought that the zinc phosphate coating equalized the reactivity of the surface with respect to the ACC bath.

[0055] In order to test the dissolution of zinc phosphate by Process C above, experiments were carried out in which panels were prepared according to Process C above. Duplicate panels were processed in which, after step 5, half of the panels were kept for zinc phosphate coating weight measurements. The other half were carried through step 6, where the epoxy coating was autodeposited over the zinc phosphate. After step 6, the panels were not cured as usual but rather were cleaned with acetone to remove the uncured film.

[0056] Scanning electron microscope analysis of the acetone-rinsed sample panels showed that a zinc phosphate coating remained. Coating weight analysis showed that the Bonderite 958 zinc phosphate was dissolved in amounts of 4-12%. 8 TABLE 3 Zinc Phosphate Coating Loss Bonderite 958 Epoxy* Substrate Initial (mg/sq. ft) Final (mg/sq. ft) % loss mils CRS 182 174  4.4 0.5 EG 192 169 12.0 0.6 A1 217 194 10.6 0.2 *Bath conditions: 5.4% solids, ox-red potential = 470 mv, F− = 155 &mgr;a, Fe titration = 24 ml.

[0057] Adhesion and Corrosion Protection Properties

[0058] Sample panels of CRS, EG and AL were coated using Processes A, B, C or D at various coating weights and submitted for adhesion and accelerated corrosion testing. The results of those tests are shown in Table 4. 9 TABLE 4 Adhesion and Corrosion Test Results Zinc Phosphate (Coating Wt. Thickness Thickness Crosshatch DI GM-9540 P4 (mg/ft2) (mm) (mm) Water Soak3 40 cycles Process Panel ID Substrate B-958 Post-Rinse AD1 ED2 Initial Final Av. Creep(mm) A A1-3 CRS 202 PLN-90 0.00 0.85 5B 5B 1.66 A B1-3 CRS 192 DIW 0.00 0.86 5B 5B 3.12 B C1-3 CRS 192 DIW 0.33 0.96 5B 5B 8.99 B D1-3 CRS 192 DIW 0.31 0.61 5B 5B 7.21 C E1-3 CRS 192 DIW 1.44 0.00 5B 3B 8.38 D F1-3 CRS  0 NA 1.18 0.00 5B 5B 18.32  A G1-3 EG 209 PLN-90 0.00 0.76 5B 5B 0.76 A H1-3 EG 210 DIW 0.00 0.83 5B 5B 1.28 B I1-3 EG 210 DIW 0.25 0.95 5B 5B 1.14 B J1-3 EG 210 DIW 0.22 0.35 5B 5B 1.15 C K1-3 EG 210 DIW 1.30 0.00 5B 5B 1.14 D L1-3 EG  0 NA 1.30 0.00 5B 1B 15.41  A M1-3 Al 215 PLN-90 0.00 0.76 5B 5B 1.21 A N1-3 Al 214 DIW 0.00 0.79 5B 5B 0.62 B O1-3 Al 214 DIW 0.31 0.57 5B 5B 0.42 C P1-3 Al 214 DIW 0.90 0.00 5B 5B 0.26 D Q1-3 Al  0 NA 0.58 0.00 5B 4B 0.36 1ACC coating bath 123-1 or 127-1 2PPG ED-5050B electrocoat primer 3ASTM D870/ASTM D3359 (5B = best adhesion, 1B = worst adhesion) 4Accelerated Corrosion Test GM 9540P, General Motors Corp 1997 Corrosion rated across the scribe using Corrosion Creepback Test Method GM 9102P, General Motors Corp 1997 (incorporated herein by reference)

[0059] Epoxy-based autodepositing coatings can therefore be used as replacements for post rinses and/or electrocoat paint. The epoxy ACC baths can coat CRS, EG and AL with or without zinc phosphate. For automotive assembly applications which typically coat multiple substrates simultaneously, a zinc phosphate or other pretreatment is required in order to equalize the reactivity of the different substrates with the ACC bath. The current ACC coating provides adhesion and corrosion protection within automotive OEM specifications for zinc and aluminum.

[0060] While embodiments of the invention have been illustrated and described, it is not intended that these embodiments illustrate and describe all possible forms of the invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the invention. 10 APPENDIX A Coating Parameters Auto Deposited Epoxy Pretreatment Fluoride Fe Coating Electrocoat Total Post ORP1 Ion % Titr. Thickness Thickness Thickness ID Substrate Formula mg/sq. ft Rinse Formula (mV) (microamps) Solids (ml) (10−3 in.) Paint (10−3 in.) (10−3 in.) A CRS B958 201.6 PLN-90 — — — — — — ED-5050B 0.85 0.85 B CRS B958 191.8 DIW — — — — — — ED-5050B 0.86 0.86 C CRS B958 191.8 DIW 127-1 380 120 13.0 22.0 0.33 ED-5050B 0.96 1.29 D CRS B958 191.8 DIW 127-1 380 160 13.0 22.0 0.31 ED-5050B 0.61 0.92 E CRS B958 191.8 DIW 123-1 475 170 12.1 22.0 1.44 — — 1.44 F CRS — — — 123-1 475 170 12.1 22.0 1.18 — — 1.18 G EG B958 208.7 PLN-90 — — — — — — ED-5050B 0.76 0.76 H EG B958 210.1 DIW — — — — — — ED-5050B 0.83 0.83 I EG B958 210.1 DIW 127-1 380 160 13.0 22.0 0.25 ED-5050B 0.95 1.20 J EG B958 210.1 DIW 127-1 380 160 13.0 22.0 0.22 ED-5050B 0.35 0.57 K EG B958 210.1 DIW 123-1 475 170 12.1 22.0 1.30 — — 1.3  L EG — — — 123-1 475 170 12.1 22.0 1.3  — — 1.3  M A1 B958 214.9 PLN-90 — — — — — — ED-5050B 0.76 0.76 6111 N A1 B958 213.5 DIW — — — — — — ED-5050B 0.79 0.79 6111 O A1 B958 213.5 DIW 127-1 380 120 13.0 22.0 0.31 ED-5050B 0.57 0.88 6111 P A1 B958 213.5 DIW 123-1 475 170 12.1 22.0 0.90 — — 0.9  6111 Q A1 — — — 131-2 260  30  8.0 0.58 — 0.58 6111 1Oxidation Reduction Potential

[0061] 11 APPENDIX B Adhesion and Corrosion Data Zinc Phosphate GM-9540 (Coating Wt. Thickness Thickness Crosshatch DI P4 Panel (mg/ft2) Post (mm) (mm) Water Soak3 Av. Creep ID Substrate B-958 Rinse AD1 ED2 Initial Final (mm) A1 CRS 202 PLN-90 0.00 0.85 5B 5B 1.61 A2 CRS 202 PLN-90 0.00 0.85 5B 5B 1.38 A3 CRS 202 PLN-90 0.00 0.85 5B 5B 1.97 B1 CRS 192 DIW 0.00 0.86 5B 5B 3.30 B2 CRS 192 DIW 0.00 0.86 5B 5B 3.07 B3 CRS 192 DIW 0.00 0.86 5B 5B 3.00 C1 CRS 192 DIW 0.33 0.96 5B 5B 7.84 C2 CRS 192 DIW 0.33 0.96 5B 5B 5.71 C3 CRS 192 DIW 0.33 0.96 5B 5B 13.44  D1 CRS 192 DIW 0.31 0.61 5B 5B 9.38 D2 CRS 192 DIW 0.31 0.61 5B 5B 5.64 D3 CRS 192 DIW 0.31 0.61 5B 5B 6.61 E1 CRS 192 DIW 1.44 0.00 5B 2B 9.38 E2 CRS 192 DIW 1.44 0.00 5B 3B 7.31 E3 CRS 192 DIW 1.44 0.00 5B 3B 8.45 F1 CRS 0 NA 1.18 0.00 5B 5B 19.27  F2 CRS 0 NA 1.18 0.00 5B 5B 18.36  F3 CRS 0 NA 1.18 0.00 5B 5B 17.34  G1 EG60 209 PLN-90 0.00 0.76 5B 5B 0.88 G2 EG60 209 PLN-90 0.00 0.76 5B 5B 0.75 G3 EG60 209 PLN-90 0.00 0.76 5B 5B 0.66 H1 EG60 210 DIW 0.00 0.83 5B 5B 1.00 H2 EG60 210 DIW 0.00 0.83 5B 5B 1.52 H3 EG60 210 DIW 0.00 0.83 5B 5B 1.31 I1 EG60 210 DIW 0.25 0.95 5B 5B 1.17 I2 EG60 210 DIW 0.25 0.95 5B 5B 1.21 I3 EG60 210 DIW 0.25 0.95 5B 5B 1.05 J1 EG60 210 DIW 0.22 0.35 5B 5B 0.86 J2 EG60 210 DIW 0.22 0.35 5B 5B 1.28 J3 EG60 210 DIW 0.22 0.35 5B 5B 1.30 K1 EG60 210 DIW 1.30 0.00 5B 5B 1.01 K2 EG60 210 DIW 1.30 0.00 5B 5B 0.98 K3 EG60 210 DIW 1.30 0.00 5B 5B 1.43 L1 EG60  0 NA 1.30 0.00 5B 0B 20.98  L2 EG60  0 NA 1.30 0.00 5B 0B 13.36  L3 EG60  0 NA 1.30 0.00 5B 1B 11.88  M1 A1 215 PLN-90 0.00 0.76 5B 4B 2.48 M2 A1 215 PLN-90 0.00 0.76 5B 5B 0.82 M3 A1 215 PLN-90 0.00 0.76 5B 5B 0.32 N1 A1 214 DIW 0.00 0.79 5B 5B 0.60 N2 A1 214 DIW 0.00 0.79 5B 5B 0.85 N3 A1 214 DIW 0.00 0.79 5B 5B 0.42 O1 A1 214 DIW 0.31 0.57 5B 5B 0.42 O2 A1 214 DIW 0.31 0.57 5B 5B 0.42 O3 A1 214 DIW 0.31 0.57 5B 5B 0.42 P1 A1 214 DIW 0.90 0.00 5B 5B 0.26 P2 A1 214 DIW 0.90 0.00 5B 5B 0.26 P3 A1 214 DIW 0.90 0.00 5B 5B 0.26 Q1 A1  0 NA 0.58 0.00 5B 3B 0.36 Q2 A1  0 NA 0.58 0.00 5B 5B 0.36 Q3 A1  0 NA 0.58 0.00 5B 4B 0.36 1ACC coating bath 123-1 or 127-1 2PPG ED-5050B electrocoat primer 3ASTM D870/ASTM D3359 (5B = best adhesion; 1B = worst adhesion) 4Accelerated Corrosion Test GM 9540P, General Motors Corp 1997. Corrosion rated across the scribe using Corrosion Creepback Test Method GM 9102P, General Motors Corp. 1997 (incorporated herein by reference)

Claims

1. A multilayered coating that is applied to a metal substrate, comprising:

a protective zone of an insoluble crystalline phosphate formed by reaction of the substrate with a zinc phosphating solution disposed upon at least a portion of the substrate; and

a film of a polymer resin that is autodeposited on the crystalline phosphate.

2. The multilayered coating of claim 1, further including a coat of paint applied to the polymer resin.

3. The multilayered coating of claim 1, further including a paint pigment contained within the polymer resin.

4. The multilayered coating of claim 1, wherein the polymer resin is autodeposited.

5. The multilayered coating of claim 2, wherein the coat of paint is applied by a method selected from the group of steps consisting of electrodepositing, spraying, rolling, brushing, powder painting, and combinations thereof.

6. The multilayered coating of claim 2, wherein the polymer resin is selected from the group consisting of an epoxy, an acrylic, polyvinylidine chloride, copolymers, and mixtures thereof.

7. A coating that is applied to a metal substrate, comprising:

a film of a polymer resin applied to the substrate, the substrate including aluminum, the polymer resin-covered aluminum substrate having the characteristics of adherence between the polymer resin and the substrate, and corrosion resistance.

8. A process for applying a multilayered coating to a metal substrate, comprising the steps of:

applying a zinc phosphating solution to at least a portion of the substrate, the zinc phosphating solution converting the surface of the substrate to an integral, protective zone of an insoluble crystalline phosphate;

rinsing the zone of crystalline phosphate; and

autodepositing a film of a polymer resin upon the rinsed crystalline phosphate.

9. The process of claim 8, further comprising a curing step.

10. The process of claim 8, further comprising the steps of:

post-rinsing the film of a polymer resin; and

electrodepositing a coat of paint upon the film of post-rinsed polymer resin.

11. The process of claim 10 further comprising the step of:

curing the autodeposited film of a polymer resin and the electrodeposited paint.

12. The process of claim 10 further comprising the steps of:

applying a number of coats of paint upon the electrodeposited coat of paint, wherein the number lies between zero and two; and

applying a clear-coat.

13. A process for applying a multilayered coating to a metal substrate, comprising the steps of:

rinsing the substrate;

autodepositing a film of a polymer resin upon the rinsed substrate;

rinsing; and

curing the autodeposited film of a polymer resin.

14. The multilayered coating of claim 2, wherein the polymer resin comprises a latex.