HK1163728B - Method for treating and/or coating a substrate with non-chrome materials - Google Patents

Description

Method for treating and/or coating a substrate with a chromium-free material

Statement regarding federally sponsored research

The invention was made with government support contract number FA8650-05-C-5010, given by the air force research laboratory of the United states. The U.S. government has certain rights in the invention.

Technical Field

The present invention generally relates to methods of treating and/or coating a substrate with a chromium-free material.

Background information

Common pretreatment and primer coating compositions for the aerospace industry contain chromium, such as at a six-price point, in order to impart corrosion resistance to the substrate on which the coating is deposited. However, due to the toxicity associated with hexavalent chromium, and in view of future governmental regulations regarding the amount of hexavalent chromium used in coatings, there is a need to reduce and/or eliminate the use of hexavalent chromium in pretreatment and primer coatings used in the aerospace industry.

Summary of The Invention

The present invention relates to a method of coating a substrate comprising: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the caustic cleaned substrate; (d) rinsing at least a portion of the substrate subjected to step (c) with water; and (e) applying a conversion coating comprising zirconium to at least a portion of the acid cleaned substrate; and wherein at least one of the materials used in steps (c) and (e) is substantially free of chromium. The invention also relates to substrates, such as aluminum substrates, which have been coated by the above-described method.

The present invention also relates to a method of coating a substrate comprising: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the caustic cleaned substrate; (d) rinsing at least a portion of the substrate subjected to step (c) with water; and (e) applying a conversion coating comprising zirconium to at least a portion of the acid cleaned substrate; and wherein the material used in steps (c) and (e) is substantially free of chromium.

The invention also relates to a method of coating a substrate consisting essentially of: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the caustic cleaned substrate; (d) rinsing at least a portion of the substrate subjected to step (c) with water; (e) applying a conversion coating comprising zirconium to at least a portion of the acid cleaned substrate; (f) rinsing at least a portion of the substrate subjected to step (e) with water; and (g) applying an electrodepositable coating composition over at least a portion of the conversion coating, wherein the electrodepositable coating composition comprises a corrosion inhibitor; and wherein the material used in steps (c), (e) and (g) is substantially free of chromium.

Detailed Description

Unless otherwise specified, all numbers used herein, such as those expressing sizes, ranges, amounts or percentages, are to be considered as having a prefix "about", even if that prefix is not expressly stated. Plural encompasses singular and vice versa. For example, while "a" caustic cleaner, "an" acid cleaner, "a" conversion coating, "an" electrodepositable coating, "a" corrosion inhibitor are listed herein, combinations (i.e., a plurality) of caustic and acid cleaners may also be used.

As used herein, "plurality" refers to two or more.

As used herein, "include" and similar terms mean "including, but not limited to".

When referring to any numerical range of values, such ranges are understood to include any number and/or any subrange between the minimum and maximum values.

As used herein, the term "cure" refers to a coating wherein any crosslinkable components of the composition are at least partially crosslinked. In certain embodiments, the cross-link density (i.e., degree of cross-linking) of the cross-linkable component ranges from 5% to 100%, such as from 35% to 85%, or, in some cases, from 50% to 85% of complete cross-linking. It is understood by those skilled in the art that the presence of degree of crosslinking (i.e., crosslink density) can be determined according to various methods, such as Dynamic Mechanical Thermal Analysis (DMTA), which is performed under nitrogen using a Polymer Laboratories MK III DMTA analyzer.

As used herein, molecular weight refers to the number average molecular weight (M)_w) As determined by gel permeation chromatography.

Any monomer(s) referenced herein generally refers to those monomers that are capable of polymerizing with another polymerizable compound, such as another monomer or polymer. Unless otherwise indicated, it should be understood that once the monomer components react with each other to form a compound, the compound will include the residues of the monomer components.

Coating process

As noted above, the present invention relates to a method of coating a substrate, such as an aluminum substrate, with a chromium-free coating system. Unlike other methods of coating aluminum substrates, the methods disclosed herein do not require the use of any chromium-containing materials (e.g., detergents, water, conversion coatings, electrodepositable coating compositions). Thus, in certain embodiments, the material used in one or more of the steps described below is substantially free of chromium. As used herein, "substantially free of chromium" means that the user has not intentionally added chromium to the material. For example, in some embodiments, all of the materials used in the following steps are substantially free of chromium. In other embodiments, one or more materials used in the following steps (e.g., conversion coatings and/or electrodepositable coating compositions) are substantially free of chromium, while other materials used in other steps (e.g., acid cleaners) can contain chromium. For the purposes of the present invention, the materials used in steps (a) to (g) may be applied to the substrate using techniques known in the art, such as spraying and/or dipping techniques.

The method begins with step (a) applying a caustic cleaner to at least a portion of the substrate. Caustic cleaners are used to remove oil and/or other contaminants (e.g., dirt or dust) that can be deposited onto a substrate surface during the forming and/or stamping process prior to applying another coating composition to the substrate. The caustic cleaner useful in the present invention may be any silicate and/or non-silicate caustic cleaner known in the art. Suitable silicate and/or non-silicate caustic cleaners include METALAST CLEANER 1000 (available from meta st International, Inc.), RIDOLENE 298 (available from HENKEL corporation), CHEMKLEEN 275 (available from ppginindustries, Inc.), or combinations thereof.

After step (a), at least a portion of the substrate that has been subjected to step (a) is subjected to the rinsing stage of step (b) and rinsed with water, such as deionized water, to wash at least a portion of the caustic cleaner from the surface of the substrate.

After step (b), (c) applying an acid cleaner to at least a portion of the substrate that has been alkaline cleaned. The acid cleaner is applied to the surface to etch the substrate surface. In certain embodiments, the acid cleaner is used to scavenge oxygen from the substrate surface (e.g., remove an oxide layer formed on the substrate surface) in order to promote uniform deposition of the conversion coating, as described below, while promoting adhesion of the conversion coating to the substrate. Suitable acid cleaners that can be used in the present methods disclosed herein include, but are not limited to, phosphoric acid, sulfuric acid, nitric acid, hydrofluoric acid, LNC DEOXIDIZER (available from Oakite), TURCO DEOXIDIZER 6 (available from Henkel), or combinations thereof.

After step (c), at least a portion of the substrate that has undergone step (c) is subjected to the rinsing stage of step (d) and rinsed with water, such as deionized water, to wash at least a portion of the acid cleaner from the substrate surface.

After step (d), then (e) depositing a conversion coating composition (pretreatment coating composition) containing zirconium onto at least a portion of the substrate that has been acid cleaned. In some embodiments, the conversion coating includes a pretreatment bath comprising 10 parts per million (ppm) to 10,000ppm zirconium based on a total weight of the pretreatment bath. In certain embodiments, the conversion coating composition may further include chromium. Conventional chromium-containing (zirconium-free) conversion coatings, which are known in the art, may also be used in conjunction with the present invention. Examples of such conventional chromium-containing conversion coatings include ALODINE1200S (available from Henkel) and/or METLAST TCP-HF (available from MetalstInternational Inc).

Additionally, in some embodiments, in lieu of the application of the conversion coating described in the preceding paragraph, the substrate surface may be anodized using techniques known in the art.

After step (e), at least a portion of the substrate that has been subjected to step (e) is subjected to the step (f) rinse stage and rinsed with water, such as deionized water, to wash at least a portion of the excess conversion coating composition from the surface of the substrate.

After step (f), (g) depositing an electrodepositable coating composition, which includes a corrosion inhibitor, onto at least a portion of the substrate on which the conversion coating has been deposited using techniques known in the art, such as anodic electrodeposition or cathodic electrodeposition techniques. In some embodiments, the electrodepositable coating composition is an anionic electrodepositable coating composition. In certain embodiments, suitable corrosion inhibitors that may be used in the electrodepositable coating composition include nitrogen-containing heterocyclic compounds. Examples of such compounds suitable for use in the present invention are azoles, oxazoles, thiazoles, thiazolines, imidazoles, diazoles, pyridines, indolizines, and triazines, tetrazoles, tolytriazoles (tolytriazoles), or mixtures thereof. Suitable triazoles include, for example, 1, 2, 3-triazole, 1, 2, 4-triazole, benzotriazole, and derivatives thereof, or combinations thereof. 1, 2, 3-triazole derivatives suitable for use in the present invention include 1-methyl-1, 2, 3-triazole, 1-phenyl-1, 2, 3-triazole, 4-methyl-2-phenyl-1, 2, 3-triazole, 1-benzyl-1, 2, 3-triazole, 4-hydroxy-1, 2, 3-triazole, 1-amino-1, 2, 3-triazole, 1-benzoylamino-4-methyl-1, 2, 3-triazole, 1-amino-4, 5-diphenyl-1, 2, 3-triazole, 1, 2, 3-triazolaldehyde, 2-methyl-1, 2, 3-triazole-4-carboxylic acid, and 4-cyano-1, 2, 3-triazole, or a combination thereof. 1, 2, 4-triazole derivatives suitable for use in the present invention include 1-methyl-1, 2, 4-triazole, 1, 3-diphenyl-1, 2, 4-triazole, 5-amino-3-methyl-1, 2, 4-triazole, 3-mercapto-1, 2, 4-triazole, 1, 2, 4-triazole-3-carboxylic acid, 1-phenyl-1, 2, 4-triazole-5-one, 1-phenylurazole, or combinations thereof. Suitable examples of diazoles and thiazoles include 2-mercaptobenzothiazole, 2, 5-dimercapto-1, 3, 4 thiadiazole and its derivatives, or combinations thereof. Derivatives of benzotriazole suitable for use in the present invention include 1-methylbenzotriazole, 5, 6-dimethylbenzotriazole, 2-phenylbenzotriazole, 1-hydroxybenzotriazole, methyl 1-benzotriazolecarboxylate, 2- (3 ', 5 ' -dibutyl2 ' -hydroxyphenyl) benzotriazole, or combinations thereof. In certain embodiments, the azole compound is present in the electrodepositable coating composition in an amount of 0.5 weight percent or more, based on the total resin solids of the electrodepositable coating composition. In certain embodiments, the azole compound is present in the electrodepositable coating composition in an amount of 5 weight percent or less, based on the total resin solids of the electrodepositable coating composition. In certain embodiments, the amount of azole compound present in the electrodepositable coating composition ranges between any combination of the values recited in the preceding sentence, inclusive of the values themselves. For example, in some embodiments, the azole compound is used in an amount of 2 wt% to 4 wt%, based on the total resin solids of the electrodepositable coating composition.

Additionally, in some embodiments, in place of the application of the electrodepositable coating composition described in the previous paragraph, a color-imparting coating composition (described in detail below) can be applied to the substrate using techniques known in the art.

In some embodiments, the method consists essentially of steps (a) through (g), wherein the material used in steps (c), (e), and (g) is substantially free of chromium.

Substrate with a coating system

The above method can be used on a variety of substrates. Suitable substrates that may be used with the present invention include metal substrates, metal alloy substrates, and substrates that have been metallized, such as nickel-plated plastic. In some embodiments, the metal or metal alloy may be steel and/or aluminum. For example, the steel substrate may be cold rolled steel, electro galvanized steel, and/or hot dip galvanized steel. Aluminum alloys of the 2XXX, 5XXX, 6XXX, or 7XXX series, as well as aluminum-plated alloys, may also be used as substrates. The substrate used in the present invention may also comprise titanium and/or titanium alloys. In some embodiments, the substrate may comprise a portion of a vehicle, such as a vehicle body (e.g., without limitation, a door, a body panel, a box deck lid, a roof panel, a hood, a roof and/or sandwich, rivets, a landing gear assembly, and/or an outer skin for an aircraft) and/or a frame of a vehicle. As used herein, "vehicle" or variants thereof include, but are not limited to, commercial and military aircraft, and/or land vehicles such as cars, motorcycles, and trucks.

The various coating compositions described herein can be applied as part of a coating system that can be deposited onto a substrate. The coating system typically includes a plurality of coating layers. A coating is typically formed when a coating composition (e.g., a primer-surfacer, color-imparting, and/or substantially clear coating composition; as described below) deposited onto a substrate is substantially cured or dried by methods known in the art (e.g., by thermal heating).

Depending on the industry (e.g., aerospace or automotive), various coatings, such as a primer-topcoat layer or a color-imparting coating, can be applied over at least a portion of the electrodepositable coating. For example, in the aerospace industry, a color-imparting coating, such as DESOPHANE (available from PPG Industries, Inc.), is deposited over at least a portion of the electrodepositable coating. In certain embodiments, a primer layer, such as DESOPRIME (available from PPG Industries, Inc), is disposed between the electrodepositable coating and the color-imparting coating.

In conventional coating systems used in the automotive industry, primer-topcoat layers, such as DPX-1791, DPX-1804, DSPX-1537, GPXH-5379, OPP-2645, PCV-70118, and 1177-225A (available from PPG Industries, Inc.) are typically deposited over at least a portion of the electrodepositable coating. The primer-topcoat coating is useful for enhancing chip resistance (e.g., color imparting and/or substantially clear coating composition) of the post-applied coating, as well as benefiting the appearance of the post-applied coating. As used herein, "primer-topcoat" refers to a primer composition underlying a post-applied coating composition and includes materials such as thermoplastics and/or crosslinked (e.g., thermoset) film-forming resins, which are generally known in the art of organic coating compositions.

It is noted that in some embodiments, the primer-topcoat coating is not used in the coating system. Thus, the color-imparting coating can be deposited over at least a portion of the electrodepositable coating.

In some embodiments, a color-imparting coating composition (hereinafter, "base coat") is deposited over at least a portion of the primer topcoat coating, if present. Any base layer coating composition known in the art may be used in the present invention. It is noted that such coating compositions typically include a colorant.

In certain embodiments, a substantially clear coating composition (hereinafter, "clear layer") is deposited over at least a portion of the base layer coating. As used herein, a "substantially transparent" coating is substantially transparent and not opaque. In certain embodiments, the substantially clear coating composition can include a colorant, however, in an amount that does not render the clear coating composition opaque (not substantially clear) after curing. Any clear layer coating composition known in the art can be used in the present invention. For example, clearcoat coating compositions described in U.S. Pat. Nos. 5,989,642, 6,245,855, 6,387,519, and 7,005,472 can be used in the coating system. In certain embodiments, the substantially clear coating composition can further include particles, such as silica particles, dispersed in the clearcoat coating composition (such as at the surface of the clearcoat coating composition after curing). In some embodiments, coating compositions including the polymers described herein may be used as clearcoat coating compositions.

One or more of the coating compositions described herein may include colorants and/or other optional materials, which are known in the art of formulating surface coatings. As used herein, the term "colorant" refers to any substance capable of imparting color and/or other opacity and/or other visual effect to a composition. The colorant can be added to the coating in any suitable form, such as discrete particles, dispersions, solutions, and/or flakes (e.g., aluminum flakes). A single colorant or a mixture of two or more colorants can be used in the coating compositions described herein.

Examples of colorants include pigments, dyes and tints, such as those used in the paint industry and/or those listed in the Color Manufacturers Association (DCMA), and special effect compositions. The colorant may include, for example, a finely divided solid powder that is insoluble but wettable under the conditions of use. The colorant may be organic or inorganic, and may be aggregated or non-aggregated. Colorants can be added to the coating by using a grinding vehicle, such as an acrylic grinding vehicle, the use of which is well known to those skilled in the art.

Examples of pigments and/or pigment compositions include, but are not limited to, carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salts (lakes), benzimidazolone, condensates (congensation), metal complexes, isoindolinone, isoindoline and polycyclic phthalocyanines, quinacridones, perylenes, perinone, diketopyrrolopyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone dyes, anthanthrone, dioxazine, triarylcarbonium, quinophthalone (quinophthalone) pigments, diketopyrrolopyrrole red ("DPPBO red"), titanium dioxide, carbon black and mixtures thereof. The terms "pigment" and "colored filler" may be used interchangeably.

Examples of dyes include, but are not limited to, those that are solvent and/or aqueous based, such as phthalocyanine green or blue, iron oxide, bismuth vanadate, anthraquinone, perylene, aluminum, and quinacridone.

Examples of dyes include, but are not limited to, pigments dispersed in water-based or water-soluble carriers such as AQUA-CHEM 896 available from Degussa, Inc, CHARISMA COLORANTS and maxinen dispersion COLORANTS available from Accurate Dispersions department of Eastman Chemical, Inc.

As noted above, the colorant may be in the form of a dispersion, including, but not limited to, a nanoparticle dispersion. Nanoparticle dispersions can include one or more highly dispersed nanoparticle colorants and/or colorant particles that produce a desired visible color and/or opacity and/or visual effect. The nanoparticle dispersion may include a colorant, such as a pigment or dye, having a particle size below 150nm, such as below 70nm, or below 30 nm. Nanoparticles can be produced by milling a coarse organic or inorganic pigment with a milling medium having a particle size below 0.5 mm. Examples of nanoparticle dispersions and methods for their preparation are defined in U.S. Pat. No.6,875,800. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation, and chemical milling (i.e., partial dissolution). To minimize re-agglomeration of nanoparticles within the coating, a resin-coated nanoparticle dispersion may be used. As used herein, "resin-coated nanoparticle dispersion" refers to a continuous phase in which are dispersed discrete "composite microparticles" comprising nanoparticles and a resin coated on the nanoparticles. Examples of resin-coated nanoparticles and methods for making the same are described in U.S. patent application publication 2005-0287348, filed 24.6.2004, U.S. provisional application No.60/482,167, filed 24.6.2003, and U.S. patent application serial No.11/337,062, filed 20.1.2006.

Examples of special effect compositions that may be used include pigments and/or compositions that produce one or more appearance effects such as reflectance, pearl gloss, metallic gloss, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromic phenomena, goniochromism (goniochromism) and/or color-change. Additional special effect compositions can provide other perceptible properties, such as opacity or texture. In a non-limiting embodiment, the special effect composition can produce a color shift such that the color of the coating changes when the coating is viewed at different angles. Examples of color effect compositions are described in U.S. Pat. No.6,894,086. Additional color effect compositions may include transparent coated mica and/or synthetic mica, coated silica, coated alumina, transparent liquid crystal pigments, liquid crystal coatings, and any composition in which interference occurs due to refractive index differences within the material, rather than due to refractive index differences between the surface of the material and the air.

In certain non-limiting embodiments, photosensitive compositions and/or photochromic compositions, which reversibly change their color upon exposure to one or more light sources, can also be used in the coating compositions described herein. Photochromic and/or photosensitive compositions can be activated by exposure to radiation of a specified wavelength. When the composition is excited, its molecular structure changes, and the changed structure shows a new color different from the original color of the composition. Upon removal of the radiation, the photochromic and/or photosensitive composition can return to an inhibited state in which it returns to its original color. In one non-limiting embodiment, the photochromic and/or photosensitive composition can be colorless in the non-excited state and exhibit color in the excited state. A full color change may occur in milliseconds to minutes, such as from 20 seconds to 60 seconds. Examples of photochromic and/or photosensitive compositions include photochromic dyes.

In non-limiting embodiments, the photosensitive composition and/or photochromic composition can be associated with and/or at least partially associated with, such as by covalent bonds, with the polymer material of the polymer and/or polymerizable component. Unlike some coatings where the photosensitive composition can migrate from the coating and crystallize into the substrate, according to one non-limiting embodiment of the present invention, the photosensitive composition and/or photochromic composition associated with and/or at least partially bound to the polymer and/or polymerizable component has minimal migration from the coating. Examples of photosensitive and/or photochromic compositions and methods for making the same are described in U.S. application serial No.10/892,919 filed on 7, 16, 2004.

In general, the colorant can be present in any amount sufficient to impart the desired visual and/or color effect. The colorant can comprise 1 to 65 weight percent of the composition, such as 3 to 40 weight percent or 5 to 35 weight percent, based on the total weight of the composition.

The coating composition may include other optional materials well known in the art of surface coating formulation such as plasticizers, antioxidants, hindered amine light stabilizers, UV light absorbers and stabilizers, surfactants, flow control agents, thixotropic agents such as bentonite clay, pigments, fillers, organic cosolvents, catalysts, including phosphonic acids and other conventional adjuvants.

It should be further understood that the one or more coating compositions forming the various coatings described herein may be "one-component" ("1K"), "two-component" ("2K"), or a multi-component composition. A 1K composition is to be understood as a composition in which all coating components remain in the same container after manufacture, during storage, etc. A 2K composition or multicomponent composition is to be understood as a composition in which the various components are kept separate until the time of application. Either the 1K or 2K coating composition can be applied to the substrate by any conventional method, such as heat, pressurized air, and the like, and cured.

The coating compositions forming the various coatings described herein can be deposited or applied to a substrate using any technique known in the art. For example, the coating composition can be applied to the substrate by any of a variety of methods including, but not limited to, spraying, brushing, dipping, and rolling. When multiple coating compositions are applied over a substrate, it should be noted that one coating composition may be applied over at least a portion of the underlying coating composition, either after the underlying coating components have cured, or before the underlying coating composition is curing. One or more uncured coating compositions may be cured simultaneously if the coating composition is applied over an underlying coating composition that has not yet been cured.

The coating composition may be cured using any technique known in the art, such as, but not limited to, thermal energy, infrared, ionizing or actinic radiation, or any combination thereof. In certain embodiments, the curing operation is carried out at a temperature ≧ 10 ℃. In other embodiments, the curing is carried out at a temperature of 246 ℃ or less. In certain embodiments, curing may be conducted at a temperature in any combination of the values recited in the preceding sentence, including the values themselves. For example, the curing can be carried out at a temperature of 120 ℃ to 150 ℃. It should be noted, however, that lower or higher temperatures may be necessary to activate the curing mechanism.

In certain embodiments, the coating compositions described herein are low temperature, moisture curable coating compositions. As used herein, the term "low temperature, moisture curable" means that the coating composition is capable of being cured in the presence of ambient air having a relative humidity of 10% to 100%, such as 25% to 80%, and a temperature of-10 ℃ to 120 ℃, such as 5 ℃ to 80 ℃, in some cases 10 ℃ to 60 ℃, and, in other cases, 15 ℃ to 40 ℃ after application to a substrate.

The dry film thickness of the coatings described herein ranges from 0.1 microns to 500 microns. In other embodiments, the dry film thickness may be 125 microns or less, such as 80 microns or less. For example, the dry film thickness ranges from 15 microns to 60 microns.

In certain embodiments of the invention described in detail, it will be apparent to those skilled in the art that various modifications and variations of the detailed description can be developed in light of the overall teachings of the invention. Accordingly, the certain aspects disclosed herein are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Examples

Example I

Bare aluminum panels of 2024-T3 were cleaned by spray rinsing with CHEMKLEEN 275 solution at 130 ° F for 2 minutes, CHEMKLEEN 275 being an alkaline cleaner available from PPG Industries. After the alkaline wash, the panel was rinsed thoroughly with deionized water. The panels were then dipped into the acidic solution at 120 ° F for two minutes. The acidic solution was obtained by diluting 198.1 grams of 85% phosphoric acid, 8.5 grams of 70% nitric acid, 16.5 grams of TRITON X-100 (from the Dow Chemical Company) and 11.1 grams of TRITON CF-10 (from the Dow Chemical Company) to five gallon volumes with deionized water, and then neutralizing to pH 3.0 with CHEMFIL Buffer (from PPG Industries). After treatment in the acid solution, the panels were thoroughly rinsed with deionized water and blow dried with hot air exhaust.

The panels were then electrocoated in an electrodeposition bath (described below) and then subjected to 50% ultrafiltration after in the bath. Electrodeposition was carried out at 100 to 170 volts for 90 seconds with bath temperatures of 24-27 ℃. After electrodeposition, the panels were all baked in a gas-heated oven at 93 ℃ (200 ° F) for 30 minutes. The electrocoated panels were then subjected to 5% neutral salt atomization according to ASTM B117 for 3000 hours.

Bath composition used in example I

Resin 1: preparation of phosphated epoxy resin dispersions

A mixture of 819.2 parts of bisphenol A diglycidyl ether (EEW 188), 263.5 parts of bisphenol A, and 209.4 parts of 2-n-butoxy-1-ethanol is heated to 115 ℃. At this time, 0.8 part of ethyltriphenylphosphonium iodide was added. The mixture was heated at least 165 ℃ and held for one hour. The mixture was allowed to cool to 88 ℃ and 51.3 parts of EKTASOLVE EEH solvent and 23.2 parts of 2-n-butoxy-1-ethanol were added. A slurry consisting of 32.1 parts of 85% o-phosphoric acid, 18.9 parts of phenylphosphonic acid, and 6.9 parts of EKTASOLVE EEH was added at 88 ℃. The reaction mixture is subsequently maintained at least 120 ℃ for 30 minutes. At this point, the mixture was cooled to 100 ℃ and 71.5 parts of deionized water was gradually added. Once water was added, it was held at about 100 ℃ for 2 hours. The reaction mixture was then cooled to 90 deg.C and 90.0 parts diisopropanolamine was added followed by 413.0 parts CYMEL 1130 and 3.0 parts deionized water. After 30 minutes of mixing, 1800.0 parts of the mixture was reverse diluted into 1506.0 parts of stirred deionized water. An additional 348.0 parts of deionized water was added to produce a uniform dispersion having a solids content of 39.5% after 1 hour at 110 ℃.

The electrodeposition bath was prepared as follows:

composition (I)	Parts by weight
		Phosphated epoxy resin dispersions	1522
Pigment paste1	331
		Deionized water	1947

¹Gray pigment paste, ACPP-1120, available from PPG Industries, Inc., 50% solids.

The above ingredients were thoroughly blended to produce a resin blend having a solids content of 19% and a pigment/binder ratio of 0.2.

Example II

Bare aluminum panels of 2024-T3 were cleaned by spray rinsing with CHEMKLEEN 275 solution at 130 ° F for 2 minutes, CHEMKLEEN 275 being an alkaline cleaner available from PPG Industries. After the alkaline wash, the panel was rinsed thoroughly with deionized water. The panels were then dipped into the acidic solution at 120 ° F for two minutes. The acidic solution was obtained by diluting 198.1 grams of 85% phosphoric acid, 8.5 grams of 70% nitric acid, 16.5 grams of TRITON X-100 (from the Dow Chemical Company) and 11.1 grams of TRITON CF-10 (from the Dow Chemical Company) to five gallon volumes with deionized water, and then neutralizing to pH 3.0 with CHEMFIL Buffer (from PPG Industries). After pickling, the panels were rinsed thoroughly with deionized water. The panels were then immersed in fluorozirconic acid at 100 ° F for two minutes. The acid bath was obtained by diluting 16.6 grams of 45% fluorozirconic acid to five gallon volume with deionized water and neutralizing to ph4.5 with CHEMFIL Buffer (available from PPG Industries). After treatment in the acidic solution, the panels were thoroughly rinsed with deionized water and air dried by hot air exhaust.

The panels were then electrocoated in an electrodeposition bath (described below), after which they were subjected to 50% ultrafiltration. Electrodeposition was carried out at 100 to 170 volts for 90 seconds with bath temperatures of 24-27 ℃. After electrodeposition, the panels were all baked in a gas-heated oven at 93 ℃ (200 ° F) for 30 minutes. The electrocoated panels were then subjected to 5% neutral salt atomization by ASTM B117 for 3000 hours.

Bath composition used in example II

Resin II: preparation of phosphated epoxy resin dispersions

A mixture of 819.2 parts of bisphenol A diglycidyl ether (EEW 188), 263.5 parts of bisphenol A, and 209.4 parts of 2-n-butoxy-1-ethanol is heated to 115 ℃. At this time, 0.8 part of ethyltriphenylphosphonium iodide was added. The mixture was heated at least 165 ℃ and held for one hour. The mixture was allowed to cool to 88 ℃ and 51.3 parts of EKTASOLVE EEH solvent and 23.2 parts of 2-n-butoxy-1-ethanol were added. A slurry consisting of 32.1 parts of 85% o-phosphoric acid, 18.9 parts of phenylphosphonic acid, and 6.9 parts of EKTASOLVE EEH was added at 88 ℃. The reaction mixture is subsequently maintained at least 120 ℃ for 30 minutes. At this point, the mixture was cooled to 100 ℃ and 71.5 parts of deionized water was gradually added. Once water was added, it was held at about 100 ℃ for 2 hours. The reaction mixture was then cooled to 90 deg.C and 90.0 parts diisopropanolamine was added followed by 413.0 parts CYMEL 1130 and 3.0 parts deionized water. After 30 minutes of mixing, 1800.0 parts of the mixture was reverse diluted into 1506.0 parts of stirred deionized water. An additional 348.0 parts of deionized water was added to produce a uniform dispersion having a solids content of 39.5% after 1 hour at 110 ℃.

Resin blends of the above phosphated epoxy resins were prepared as follows:

composition (I)	Parts by weight
		Phosphated epoxy resin Dispersion + Corrosion inhibitor of example 1	1522
Pigment paste 1	331
		Deionized water	1947

¹The color of the gray pigment paste, ACPP-1120,available from PPG Industries, inc., 50% solids content.

The above ingredients were thoroughly blended to produce a resin blend having a solids content of 19% and a pigment/binder ratio of 0.2.

Summary of test results

The test results show that the panel of example I I exhibits improved corrosion performance (i.e., less blistering; facer and scratch), less corrosion at the scratch, and fewer dents when compared to the panel of example I.

Claims (14)

1. A method of coating a substrate comprising: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the substrate that has been caustic cleaned; (d) rinsing at least a portion of the substrate subjected to step (c) with water; and (e) depositing a conversion coating composition comprising zirconium onto at least a portion of the acid cleaned substrate; wherein at least one material used in steps (c) and (e) is substantially free of chromium; (f) rinsing at least a portion of the substrate subjected to step (e) with water; and (g) depositing an electrodepositable coating composition onto at least a portion of the conversion coating, wherein the electrodepositable coating composition comprises a corrosion inhibitor, wherein the corrosion inhibitor comprises an azole compound.

2. The method of claim 1, wherein the electrodepositable coating composition is substantially free of chromium.

3. The method of claim 1, wherein the azole compound comprises benzotriazole, 3-mercapto-1, 2, 4-triazole, 2-mercaptobenzothiazole, 2, 5-dimercapto-1, 3, 4 thiadiazole, 1-methylbenzotriazole, or combinations thereof.

4. The method of claim 1, wherein the electrodepositable coating composition comprises an ungelled phosphated epoxy resin, wherein the phosphated epoxy resin comprises a mixture of the reaction product of a polymeric epoxy compound and phosphoric acid, an organophosphonic acid, an organophosphinic acid, or a combination thereof.

5. The method of claim 1, wherein the acid cleaner comprises phosphoric acid, sulfonic acid, hydrofluoric acid, nitric acid, or a combination thereof.

6. The method of claim 1, wherein the conversion coating composition is substantially free of chromium.

7. A method of coating a substrate comprising: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the substrate that has been caustic cleaned; (d) rinsing at least a portion of the substrate subjected to step (c) with water; (e) depositing a zirconium-containing conversion coating composition onto at least a portion of the acid cleaned substrate; wherein the material used in steps (c) and (e) is substantially free of chromium; (f) rinsing at least a portion of the substrate subjected to step (e) with water; and (g) depositing an electrodepositable coating composition onto at least a portion of the conversion coating, wherein the electrodepositable coating composition comprises a corrosion inhibitor, wherein the corrosion inhibitor comprises an azole compound.

8. The method of claim 7, wherein the azole compound comprises benzotriazole, 3-mercapto-1, 2, 4-triazole, 2-mercaptobenzothiazole, 2, 5-dimercapto-1, 3, 4 thiadiazole, 1-methylbenzotriazole, or combinations thereof.

9. The method of claim 7, wherein the electrodepositable coating composition comprises an ungelled phosphated epoxy resin, wherein the phosphated epoxy resin comprises a mixture of the reaction product of a polymeric epoxy compound and phosphoric acid, an organophosphonic acid, an organophosphinic acid, or a combination thereof.

10. A method of coating a substrate consisting essentially of: (a) applying a caustic cleaner over at least a portion of the substrate; (b) rinsing at least a portion of the substrate subjected to step (a) with water; (c) applying an acid cleaner to at least a portion of the substrate that has been caustic cleaned; (d) rinsing at least a portion of the substrate subjected to step (c) with water; (e) applying a conversion coating composition comprising zirconium to at least a portion of the acid cleaned substrate; (f) rinsing at least a portion of the substrate subjected to step (e) with water; and (g) applying an electrodepositable coating composition over at least a portion of the conversion coating composition, wherein the electrodepositable coating composition comprises a corrosion inhibitor, wherein the corrosion inhibitor comprises an azole compound; and wherein the material used in steps (c), (e) and (g) is substantially free of chromium.

11. The method of claim 10, wherein the azole compound comprises benzotriazole, 3-mercapto-1, 2, 4-triazole, 2-mercaptobenzothiazole, 2, 5-dimercapto-1, 3, 4 thiadiazole, 1-methylbenzotriazole, or combinations thereof.

12. The method of claim 10, wherein the electrodepositable coating composition comprises an ungelled phosphated epoxy resin, wherein the phosphated epoxy resin comprises a mixture of the reaction product of a polymeric epoxy compound and phosphoric acid, an organophosphonic acid, an organophosphinic acid, or a combination thereof.

13. A substrate coated according to the method of claim 1.

14. The substrate of claim 13, wherein the substrate is aluminum.