JP2008537975A - Composition and method for protective coating of metal substrates - Google Patents

Abstract

A novel composition for anticorrosion coating on various metal substrates and methods of using the composition are provided.
At least one trivalent chromium compound, at least one fluorozirconate, at least one carboxylic acid compound and / or polyhydroxy compound, at least one corrosion inhibitor and optionally an effective amount of a fluorometal compound ( Effective amounts of acidic aqueous solutions containing, for example, fluorotitanic acid, fluorotantalate, fluoroborate, fluorosilicate), divalent zinc compounds, surfactants, wetting agents and / or thickeners, and use thereof A method for treating metal substrates.
[Selection figure] None

Description

(Statement of government relations)
The present invention was made by a United States government employee who is manufactured or used by the United States government for government purposes and does not incur any royalty payments for the product or its use.

(Related application)
This patent application is a continuation-in-part of co-pending patent application NC-96,343 (filing date: April 21, 2005).

(Technical field)
The present invention relates to compositions for preparing protective coatings on various metal substrates and methods of using said compositions. The method comprises at least one trivalent chromium compound, at least one fluorozirconate salt, at least one carboxylic acid compound and / or polyhydroxy compound, at least one corrosion inhibitor and optionally an effective amount of a fluorometal compound ( Metal substrates using an effective amount of acidic aqueous solution containing, for example, fluorotitanic acid, fluorotantalate, fluoroborate, fluorosilicate), divalent zinc compounds, surfactants, wetting agents and / or thickeners Processing. The present invention specifically treats various metal substrates, including stable acidic aqueous solutions and pre-coated metal substrates such as anodized aluminum, to improve the adhesion and corrosion protection properties of metal substrates. On how to do. The method comprises an effective amount of at least one water-soluble trivalent chromium salt, at least one water-soluble hexafluorozirconate salt, at least one water-soluble poly or monocarboxylic acid compound and / or polyhydroxy compound, and at least Treating the metal substrate with a stable acidic aqueous solution comprising one water-soluble pitting or corrosion inhibitor. Further, in order to improve the color tone and stability of the acidic solution, the compound which may be added in a small amount but in an effective amount includes at least one water-soluble hexa or tetrafluoro metal compound, a divalent zinc salt and an effective amount. An amount of water-soluble thickener and / or water-soluble surfactant is included.

  The present invention includes aqueous solutions or compositions containing specific chemicals and relates to methods for applying coatings derived from these chemicals onto various metal substrates, such as substrates that have already been pre-coated with metals. For example, the composition or solution may be used in particular for corrosion protection by coating with aluminum and an aluminum alloy (i.e., an aluminum conversion coating) and for enhancing adhesion to paint, for enhancing corrosion protection by sealing treatment by anodization, titanium or titanium alloy Reinforcement of adhesion with paint by treatment of coating, strengthening of adhesion with paint and corrosion protection by treatment of magnesium alloy, strengthening of adhesion with paint and rust prevention by treatment of steel, and after phosphate treatment Useful for enhancing paint adhesion and corrosion protection by treatment, sacrificial coating with zinc, zinc-nickel, tin-zinc and cadmium on ferrous alloys and other metal substrates such as steel.

Many of the pre-treatment, post-treatment and sealing solutions currently used are based on the use of hexavalent chromium compounds. Hexavalent chromium is extremely toxic and is known to have carcinogenicity.
As a result, the solutions used in these coating processes and the coatings themselves are toxic. However, hexavalent chromium films or coatings provide significant paint adhesion, good corrosion resistance, and low electrical resistance, which can be easily applied by dipping, spraying or coating techniques. However, the presence of environmental laws, government mandates and local occupational, safety and health regulations (OSH) forces military and commercial users to search for alternative technologies. In addition, the use of hexavalent chromium coatings becomes increasingly expensive as regulations become more rigorous, and the costs increase due to future PEL regulations imposed by the Environmental Protection Agency and OSHA. Furthermore, certain techniques, such as spraying with chromic acid solutions, are prohibited in some facilities due to enforcement by OSH, which forces the use of suboptimal alternative solutions. In summary, although the hexavalent chromic acid coating is technically superior, it is highly desirable to provide a modified example in view of life cycle cost, environment, and OSH. In view of the above background, alternative methods for surface treatment of metals that are technically equivalent to or superior to hexavalent chromic acid coatings, which have no environmental and health problems, are currently being developed.

  However, regardless of whether it is a composition or a method of use, in these many variations, the solid components tend to separate from the solution and precipitate, especially after many uses. During the precipitation over time, the active compound is precipitated as an insoluble solid, which may reduce the effect as a coating solution. Furthermore, precipitation of solids can cause clogging of filters, lines and pumps in both immersion and spray coating. Therefore, a more suitable composition is required in order to improve the storage stability of the acidic solution and not to prevent the precipitation process or the subsequent work using the coating by the precipitation.

  The present invention relates to compositions and treatment methods for anti-corrosion coatings on various metal substrates, including pre-coated (eg, phosphate coated or anodized coated) metal substrates, which methods are trivalent. Treatment of the metal substrate with an acidic aqueous solution comprising a chromium (III) compound, a fluorozirconate salt, a corrosion inhibitor or pitting inhibitor (eg, triazole) and a stabilizer. One or more of a fluorometal compound, a surfactant, a thickener and a divalent zinc compound may optionally be added to the acidic solution. By utilizing the present invention, the adhesion between the metal surface and a coating film such as a paint can be improved, and the corrosion prevention characteristics of the metal surface (eg, aluminum, steel, galvanized surface, etc.) can be improved. More specifically, the acidic solution of the present invention also includes an effective amount of at least one water-soluble corrosion inhibitor or pitting inhibitor, and a stabilizer comprising a polyhydroxy compound and / or a water-soluble carboxylic acid compound ( One or more carboxylic acids having a functional group represented by the general formula R—COO—, wherein R is hydrogen or a low molecular organic radical or functional group). Stabilizers, i.e. carboxylic acid compounds, can be used in the form of their acids or salts. In some cases, the salts of the carboxylic acid stabilizers outperform those acids. For example, organic acids (formic acid, acetic acid, glycolic acid, propionic acid, citric acid, and other short chain or low molecular weight carboxylic acids) that exhibit a buffering action in a weakly acidic pH range can be used as a solution stabilizer. By adding a polyhydroxy-based or carboxylic acid-based stabilizer to the acidic solution, it is possible to prolong the expiration date of the solution and to improve the stability during use. In the acidic solution to which the stabilizer was added, precipitation did not substantially occur in the evaluation when the expiration date of 24 months passed, and any decrease in coating performance such as precipitation did not occur.

  1 to 6 show the performance improvement of an aluminum alloy with a similar coating with a triazole-containing solution of the present invention compared to a coating without triazole for corrosion protection.

  In view of the above, an object of the present invention is to provide a metal substrate (including a pre-coated substrate) comprising a trivalent chromium compound, a fluorozirconate, a polyhydroxy compound or a carboxylic acid compound, and an effective amount of an inhibitor. It is to provide a stable acidic aqueous solution for increasing the adhesion and corrosion resistance of metals used in coatings.

  Another object of the present invention is at a pH of about 1.0 to 5.5 comprising a trivalent chromium compound, a fluorozirconate, an anti-pitting compound, and at least one polyhydroxy compound and / or carboxylic acid compound. It is to provide a stable acidic aqueous solution for treating metal substrates with or without metal pre-coating.

  Another object of the present invention is to provide a method for treating a metal substrate for the purpose of providing distinguishable color to coating, good adhesion and improved corrosion resistance.

  Another object of the present invention comprises a trivalent chromium compound, a hexafluorozirconate salt, a corrosion inhibitor, and at least one carboxylic acid or polyhydroxy compound with a pH of about 2.5-4.5. The present invention provides a stable acidic aqueous solution for treating a metal substrate at a room temperature or higher and substantially free of hexavalent chromium.

  These and other objects of the present invention will become apparent upon reference to the following detailed description taken in conjunction with the accompanying FIGS.

The present invention provides a stable acidic aqueous solution, as well as a zirconium-chromium coating by, for example, chemical conversion treatment on a metal substrate including a pre-coated substrate (such as a substrate coated with anodized aluminum or phosphate). , PH about 1.0-5.5, preferably about 2.5-4.5 or 3.4-4.0 to improve the adhesion and corrosion resistance of metals. Known phosphate coating treatments include, for example, treatment with zinc phosphate, iron phosphate, manganese phosphate and calcium phosphate-zinc phosphate mixture. The method includes the use of an acidic aqueous solution at a temperature of about 48.9 ° C. or higher (eg, up to about 93.3 ° C.). The solution contains at least one water-soluble trivalent chromium compound (e.g. chromium sulfate) at about 0.01-100 g, preferably about 0.01-22 g or 5.0-7.0 g, at least one fluoro zirconate (e.g. alkali metal salts of _H 2 ZrF ₆₎ is approximately solution per 1L 0.01～24G, preferably about 1.0~12g or 1.0～6.0G, water-soluble corrosion An inhibitor or anti-pitting agent (e.g., benzotriazole) in an amount effective to prevent corrosion, e.g., about 0.001 to 4.0 grams per liter, preferably about 0.25 to 2.0 grams per liter or about 0.25 1.0 g and at least one water selected from the group consisting of carboxylic acid compounds, polyhydroxy compounds and mixtures in any ratio of any of these stabilizers Sex stabilizers or compounds, of solution per 1L, about 0.001～2.0G, preferably included 0.001-1.0 moles or 0.01 to 1.0 mol. If required, each of the compounds of the present invention can be used in amounts up to their solubility limit in aqueous acid depending on the metal surface being treated. The metal surface to be treated according to the present invention may be any metal substrate, for example, steel surfaces such as iron, zinc, magnesium, galvanized steel, and aluminum and aluminum alloys. Any metal surface, including a metal surface with a protective coating or metal pre-coating, can be treated with the composition of the present invention.

  After cleaning and deoxy soy or pickling, the coating is applied to a metal substrate (eg, an aluminum substrate that has undergone conventional mechanical or chemical treatment). The acidic solution of the present invention is applied to a metal substrate at room temperature by dipping, spraying or painting techniques similar to those used for other metal treatments. The residence time of the solution ranges from about 1.0 to 60 minutes or longer. With this solution, optimum film color change, paint adhesion and corrosion resistance are obtained during a residence time of 1.0 to 40 minutes or 1.0 to 10 minutes. With a residence time of 1.0 to 10 minutes, the coating exhibits a significant color change, mainly depending on the chemical composition of the aqueous solution. The remaining solution is then washed away from the metal substrate using tap or deionized water.

  In some methods, by adding a thickener to the solution depending on the physical characteristics of the metal substrate (eg, the physical dimensions of the steel or aluminum substrate), solution evaporation is delayed and optimal during spraying and painting. Thin film formation is encouraged. This also makes it difficult to form powders that reduce paint adhesion. The addition of thickeners also facilitates proper film formation when applied to large areas and mitigates the dilution effect due to the wash water remaining on the substrate in the process following the previous process. This feature of the method results in a scratch-free film or coating with improved color and corrosion protection. A water-soluble thickener such as a cellulose compound can be added to the acidic aqueous solution in an amount of about 0.0 to 20 g per liter, preferably 0.5 to 10 g (for example, about 0.1 to 5.0 g per liter of aqueous solution). Furthermore, depending on the characteristics of the metal substrate, an effective amount, but a minor amount of at least one water-soluble surfactant or wetting agent is added in an amount of about 0.0 to 20 g, preferably 0.5 to 10 g (eg 1 L of acidic solution). Can be added to the acidic solution in an amount of 0.1 to 5.0 g per unit. Many water-soluble surfactants are known in the prior art, and therefore, in the present invention, surfactants can be selected from the group consisting of nonionic, cationic and anionic surfactants.

The trivalent chromium is added to the solution as a water-soluble trivalent chromium compound (as a liquid or solid, preferably a trivalent chromium salt). Specifically, when preparing the acidic aqueous solution of the present invention, it is preferable to add a chromium salt to the solution to obtain an aqueous chromium having a valence of +3. For _{example, Cr 2 (SO 4) 3} , (NH 4) in the form of Cr (SO 4) 2, Cr (NO) 3 · 9H 2 O or KCr _{(SO 4) 2} and any chromium compound mixtures of these compounds It is preferable to add to the solution. The preferred trivalent chromium salt concentration is about 5.0 to 7.0 g per liter of aqueous solution. It has been found that particularly good results are obtained by these methods when the trivalent chromium compound is present in solution at a suitable concentration.

  The acidic solution may include at least one divalent zinc compound, which provides coloration and improves the corrosion protection of the substrate compared to other treatments or compositions that do not contain zinc. The amount of the zinc compound can be adjusted to 0.0 to 100 g, particularly about 0.001 g to 10 g (per liter) (for example, 0.5 to 2.0 g of Zn2 + cation) when adjusting the color tone to be applied to the coating. The divalent zinc may be supplied by any chemical (eg, a salt that is water soluble at the required concentration and compatible with the other components of the acidic solution). The divalent zinc compound that is water-soluble at the required concentration is preferably zinc acetate, zinc telluride, zinc tetrafluoroborate, zinc molybdate, zinc hexafluorosilicate, zinc sulfate, etc., or any ratio thereof. All combinations are exemplified. The treatment or coating of the metal substrate can be performed at a suitable solution temperature from ambient temperature (eg, room temperature) to about 48.9 ° C. or higher (up to about 93.3 ° C.). However, room temperature is preferred in that no heating device is required. The coating may be air dried by any known method such as oven drying, air jet drying, infrared lamp exposure, and the like.

  The following examples illustrate the use of the above solution for applying a stable acid solution of the present invention and a coating with improved colorability, adhesion and corrosion resistance to a metal substrate comprising a metal substrate that already has a metal coating. Indicates.

<Example 1>
To 1 L of deionized water, 4.0 g of potassium hexafluorozirconate, 3.0 g of chromium (III) sulfate (base), 0.12 g of potassium tetrafluoroborate and 0.25 g of benzotriazole are added. did. The solution was stirred until all compounds were dissolved. The solution was allowed to stand at room temperature (21.1 ° C. to 26.7 ° C.) until the pH reached 3.70.

<Example 2>
In 1 L of deionized water, 4.0 g of potassium hexafluorozirconate, 3.0 g of chromium (III) sulfate (base), 2.3 g (0.025 mol) of glycerol and 0.25 g of benzotriazole Was added. The solution was stirred until all compounds were dissolved. The solution was allowed to stand at room temperature (21.1 ° C. to 26.7 ° C.) until the pH reached 3.55.

<Example 3>
To 1 L of deionized water, 4.0 g of potassium hexafluorozirconate and 3.0 g of chromium (III) sulfate (base) were added. The solution was stirred until all compounds were dissolved. The pH was maintained at 3.25 to 3.50 for 14 days with dilute sulfuric acid and diluted with potassium hydroxide to adjust the final pH to 3.90. 0.25 g of benzotriazole was added.

<Example 4>
A solution similar to Example 2 was prepared (except that benzotriazole was replaced with 0.50 g of 2-mercaptobenzimidazole).

<Example 5>
A solution was prepared in the same manner as in Example 3 (however, in addition to benzotriazole, 0.25 g of 2-mercaptobenzimidazole was added).

<Example 6>
A solution was prepared as in Example 1 (but 0.25 g 2-mercaptobenzimidazole and 0.25 g 2-mercaptomenzazole were added in addition to benzotriazole).

<Example 7>
Using the compositions of Examples 1, 2 and 3, an aluminum alloy (2024-T3) panel was coated by the following procedure. The method included cleaning a 5 inch × 3 inch × 0.030 inch panel (2024-T3) with Turco 425 for 15 minutes at 60 ° C. Backwashing was performed in cascade with warm tap water. Immediately after, the test piece was immersed in TurcoSmut Go for 5 minutes. Backwash was performed in a cascade manner with room temperature tap water. Immediately afterwards, the panel was immersed in the compositions of Examples 1, 2 and 3 at 21.1 to 26.7 ° C. for 5 minutes. Backwash was performed in a cascade manner with room temperature tap water. Final wash with deionized water. The panel was air dried and allowed to stand overnight. The coating was subjected to the next coating step for testing or with a final organic coating such as, for example, (MIL-PRF-23377) epoxy primer.

<Example 8>
The test plate was washed and coated as described in Example 7, and then neutral salt mist (ASTM B 117) with 6 gradients from vertical. The coating performance after 3 weeks (21 days) of salt fog is shown in FIGS. As a control coating, the compositions of Examples 1, 2, and 3 without triazole were prepared. As is apparent from FIGS. 1 to 6 (photos), the addition of corrosion inhibitors resulted in favorable corrosion resistance in coatings having different compositions.

  The pitting inhibitor or corrosion inhibitor is a water soluble compound selected from the group consisting of triazoles, benzimidazoles, benzazoles, benzoxazoles and mixtures of these inhibitors in any proportion. Preferred corrosion inhibitors or anti-pitting compounds include triazoles (such as alkyl and preferably aryl triazoles) comprising up to 12 carbon atoms. Aryl triazoles contain 6 to 10 carbon atoms (eg compounds such as benzotriazole and tolyltriazole) and alkyltriazoles contain up to 6 carbon atoms (eg methyl or ethyl triazole). Triazoles such as benzotriazole are commercially available under the trade name COBRATEC. The anti-corrosion inhibitor is an effective amount sufficient to inhibit corrosion, preferably about 0.001-4.0 g per liter, more preferably about 0.25-2.0 g or 0.25-1.0 g. Dissolve in solution by volume. Other useful triazoles include water-soluble hydroxybenzotriazoles such as hydroxy 4-alkylbenzotriazole derivatives, hydroxy-6-benzotriazole, hydroxy-5-chlorobenzotriazole, hydroxy 6-carboxybenzotriazole, hydroxy-5-alkyl. Examples include benzotriazole.

  Examples of the carboxylic acid compound as a stabilizer added to the acidic aqueous solution include water-soluble carboxylic acids such as adipic acid, citric acid, acetic acid, citraconic acid, fumaric acid, glutaric acid, tartaric acid or ethylenediaminetetraacetic acid, and salts thereof. Water-soluble acids and / or carboxylates (wherein the hydrocarbon chain on the carboxyl group does not contain a significant number of carbon atoms so as to reduce the solubility of the compound). By employing a combination of two or more of salts and / or acids, a specific pH can be adjusted. For example, low molecular acids and / or salts such as potassium formate or citrate at a concentration of at least 0.001 to 1.0 mole per liter are used. These compounds are good for all stabilizers. Particularly good results were obtained with an acidic solution prepared by adding about 0.01 mol of potassium formate per liter 4 days after the initial solution preparation. Good results are obtained when the stabilizer is a carboxylic acid compound comprising a hydroxy group and a carboxyl group (for example compounds such as citric acid, glycolic acid, lactic acid, gluconic acid, glutaric acid and their salts). .

  In addition to the carboxylic acid compound as a stabilizer, the polyhydroxy compound is present in a minor but effective amount (approximately 0.001 to 2.0 moles, preferably 0.01 to 2.0 moles or 0.1 mole per liter). 01-1.0 mol) may be used as a stabilizer. Examples of the compound include trihydrogen compounds (for example, glycerol) and dihydrogen-containing ether alcohols (for example, glycol ethers (alkylene glycol ethers and the like (for example, methylene glycol ether, propylene glycol ether, tripropylene glycol ether, diethylene glycol ether)). ). Other glycols (low molecular weight compounds such as ethylene glycol, propylene glycol, butylene glycol, cyclohexanol), as well as water soluble poly (oxyalkylene glycols) such as poly-oxyethylene or poly-oxypropylene glycol (less than about 1000 low Having a molecular weight))) may be used to improve the stability and dispersibility of solids in a coating bath or in an acidic solution Other known dihydrogen and trihydrogen aliphatic alcohols include water Lower alkanols, such as dihydrogen and trihydrogen containing alkanols containing up to 12 carbon atoms, which are dialkylene and trihydrogen lower alkanols, which contain up to 10 carbon atoms in the alkylene group. Glycols containing atoms (eg trimethylene glycol) ), And polyglycols (eg, diethylene glycol, methylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dibutylene glycol, tributylene glycol and other polyalkylene glycols having 2 to 8 alkylene radicals Carbon atoms, preferably from 2 to 4 carbon atoms) The combination or mixture of carboxylic acids and polyhydroxy stabilizers may be used in acidic solutions in any ratio.

  In addition to polyhydroxy and carboxylic acid stabilizers, the acidic aqueous solution contains a trace amount but an effective amount (0.0-24 g, for example 0.01-12 g per liter of solution) of at least one fluorometal compound (hexa Compounds such as fluorotitanate, heptafluorotantalate, tetrafluoroborate and hexafluorosilicate).

  In preparing the acidic solution of the present invention, a known water-soluble surfactant is added in a trivalent chromium solution in an amount of about 0 to 20 g, preferably about 5.0 to 10 g or 1.0 to 5.0 g per liter. You may add to. By adding the surfactant to the aqueous solution, good wettability due to a decrease in the liquid surface tension can be obtained, whereby a uniform thin film can be formed on the entire surface of the metal substrate. Surfactants include at least one water soluble compound selected from the group consisting of nonionic, anionic and cationic surfactants. Known water-soluble surfactants include monocarboxyimidazoline, alkyl sulfate sodium salt (DUPONOL®), tridecyloxypoly (alkylenoxyethanol) ethoxylated or propoxylated alkylphenol (IGEPAL®), alkyl Sulfonamide, alkaryl sulfate, palmitic alkanolamide (CENTROL (registered trademark)), octylphenyl polyethoxyethanol (TRITON (registered trademark)), sorbitan monopalmitate (SPAN (registered trademark)), dodecyl phenyl polyethylene glycol ether ( For example, TERGITROL (registered trademark), alkyl pyrrolidone, polyalkoxylated fatty acid ester, alkylbenzene sulfonic acid, and mixtures thereof. Other known water-soluble surfactants include, for example, ethylene oxide adducts with nonylphenol ethoxylates and aliphatic amines ("Surfactants and Detersive Systems", by John Wiley et al. In Kirk-Othmer's Encyclo) See Chemical Technology, 3rd Ed.).

  When the surface cannot be immersed due to a large surface area or when spraying on a vertical surface, a thickener is added to maintain the contact condition with the aqueous solution on the surface. As the thickener to be used, water-soluble inorganic and organic thickeners are known. For example, an effective amount with respect to a trivalent chromium solution (0 to 10 g per liter of acidic solution, preferably 0.5 to 1. 5 g) can be added. Specific examples of suitable thickeners include cellulose compounds such as hydroxypropylcellulose (such as crucelle), ethyl cellose, hydroxyethylcellulose, hydroxymethylcellulose, methylcellulose and mixtures thereof. Other suitable water soluble inorganic thickeners include colloidal silica, clays such as bentonite, starch, gum arabic, gum tragacanth, agar and various combinations.

  After coating the surface of the metal substrate by a conventional method, the solution can be applied by dipping, spraying or applying. The TCP solution of the present invention can be used at a high temperature of 48.9 ° C. or lower, or higher (eg, up to 93.3 ° C.), and more optimally, a dipping process to improve the corrosion resistance of the coating. Apply with. The residence time in the solution is about 13.8 minutes or more at about 23.8 ° C. or higher, preferably 1.0 to 40 minutes or 1.0 to 10 minutes. After residence, the remaining solution is tapped off the substrate or washed thoroughly with deionized water. No additional chemical manipulation of the laminated film is necessary to achieve good performance. The aqueous solution may be sprayed from a spray tank designed as an alternative to a dip tank.

  While the invention has been described in terms of many specific embodiments, it will be apparent that other variations and modifications may be made without departing from the scope of the invention as defined in the following claims.

(Photo) Demonstrates the degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 1 that does not contain a triazole inhibitor. (Photo) Demonstrates the degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 1 containing a benzotriazole inhibitor. (Photo) Degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 2 that does not contain a triazole inhibitor. (Photo) Demonstrates the degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 2 containing a benzotriazole inhibitor. (Photo) Demonstrates the degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 3 that does not contain a triazole inhibitor. (Photo) Demonstrates the degree of corrosion of an aluminum alloy (2024-T3) panel having a chemical conversion coating with the composition of Example 3 containing a benzotriazole inhibitor.

Claims (40)

  A method of coating a metal substrate for improving corrosion protection and adhesive bonding of a metal comprising treating the metal substrate with an effective amount of an acidic aqueous solution having a pH of about 1.0 to 5.5, wherein the acidic aqueous solution comprises: About 0.01-100 g of at least one trivalent chromium compound, about 0.01-24 g of at least one fluorozirconate, effective amount of triazole, benzimidazole, benzazole and benzoxa per liter of solution. At least one water-soluble corrosion inhibitor selected from the group consisting of sols, about 0.0-100 g of a divalent zinc compound, about 0.0-20 g of a surfactant, about 0.0-20 g of thickening; And a safe amount selected from the group consisting of an effective amount of a polyhydroxy compound, a carboxylic acid compound and a mixture of a polyhydroxy compound and a carboxylic acid compound. The method comprising the agent.   The method of claim 1, wherein the metal substrate has a metal pre-coating on its surface.   The method of claim 2, wherein the substrate having the metal pre-coating is anodized aluminum.   The method of claim 2, wherein the substrate having the metal pre-coating is a phosphate coating.   The method of claim 1, wherein the metal substrate is an aluminum alloy.   The method of claim 1, wherein the metal substrate is an iron alloy.   The method of claim 1, wherein the carboxylic acid compound is a hydroxycarboxylic acid compound and the corrosion inhibitor is benzotriazole.   The method according to claim 7, wherein the hydroxycarboxylic acid compound is citric acid and a water-soluble salt thereof.   The method according to claim 7, wherein the hydroxycarboxylic acid compound is glycolic acid and a water-soluble salt thereof.   The method according to claim 7, wherein the hydroxycarboxylic acid compound is gluconic acid and a water-soluble salt thereof.   The method according to claim 1, wherein the carboxylic acid compound is formic acid and a water-soluble salt thereof, and the corrosion inhibitor is benzotriazole.   The method according to claim 1, wherein the carboxylic acid compound is propionic acid and a water-soluble salt thereof.   The method according to claim 1, wherein the acidic aqueous solution contains about 0.001 to 1.0 mol of carboxylic acid compound per liter, and the inhibitor is triazole.   The method of claim 1, wherein the acidic aqueous solution comprises about 0.001 to 2.0 moles of stabilizer per liter and 0.025 to 4.0 grams of triazole per liter.   15. The method of claim 14, wherein the stabilizer is glycerol and the triazole inhibitor is a mixture of benzotriazole and tolyltriazole.   The method according to claim 14, wherein the stabilizer is a carboxylic acid compound having a plurality of functional carboxyl groups per molecule.   A metal substrate coating composition for improving corrosion protection and adhesive bonding of metals, having a pH of about 1.0 to 5.5 and at least one of about 0.01 to 100 g per liter of solution. An acidic aqueous solution containing a divalent chromium compound, about 0.01 to 24 g of at least one fluorozirconate, an effective amount of at least one water-soluble substance selected from the group consisting of triazole, benzimidazole, benzazole and benzoxazole. Corrosion inhibitor, about 0.0-20 g divalent zinc compound, about 0.0-20 g surfactant, about 0.0-20 g thickener, and an effective amount of polyhydroxy compound, carvone A composition comprising a stabilizer selected from the group consisting of acid compounds and mixtures of polyhydroxy compounds and carboxylic acid compounds.   The composition according to claim 17, wherein the stabilizer is a carboxylic acid compound having a plurality of functional carboxyl groups per molecule.   The composition according to claim 17, wherein the carboxylic acid compound is an oxycarboxylic acid and a water-soluble salt thereof.   The composition according to claim 19, wherein the hydroxycarboxylic acid compound is citric acid and a water-soluble salt thereof.   The composition according to claim 19, wherein the hydroxycarboxylic acid compound is glycolic acid and a water-soluble salt thereof.   The composition according to claim 19, wherein the hydroxycarboxylic acid compound is lactic acid and a water-soluble salt thereof.   The composition according to claim 17, wherein the carboxylic acid compound is formic acid and a water-soluble salt thereof, and the inhibitor is benzotriazole.   The composition according to claim 17, wherein the carboxylic acid compound is propionic acid and a water-soluble salt thereof.   The composition according to claim 17, wherein the polyhydroxy compound is glycerol, the carboxylic acid compound is a low-molecular carboxylic acid or a water-soluble salt thereof, and the inhibitor is triazole.   18. The composition of claim 17, wherein the stabilizer is a mixture of a low molecular carboxylic acid and a polyhydroxy compound.   18. The composition of claim 17, wherein the stabilizer is a low molecular weight polyhydroxy compound and the inhibitor is mercaptobenzimidazole.   18. The composition of claim 17, wherein the polyhydroxy compound is glycerol and the inhibitor is benzotriazole.   18. The composition of claim 17, wherein the zinc compound is a water-soluble zinc salt and is present in an acidic aqueous solution in an amount of about 0.5-2.0 g and the inhibitor is benzotriazole.   18. The composition of claim 17, wherein the at least one polyhydroxy compound is glycerol and the inhibitor is a mixture of triazoles.   18. The composition of claim 17, wherein the polyhydroxy compound is a polyalkylene glycol and the inhibitor is benzimidazole.   The pH range is about 2.5 to 4.5, the trivalent chromium compound is about 0.01 to 22 g per liter of the solution, and the fluorozirconate that is hexafluorozirconate is about 1.0 to about 18. The composition of claim 17, comprising 12 g, about 0.001 to 1.0 mole of the stabilizer, and about 0.001 to 4.0 g of the inhibitor that is a triazole.   33. The composition of claim 32, wherein the stabilizer is a low molecular carboxylic acid or a water soluble salt thereof and the triazole is tolyltriazole.   18. The composition of claim 17, wherein the stabilizer is a polyhydroxy compound and the corrosion inhibitor is mercaptobenzazole.   18. The composition of claim 17, wherein the zinc compound is included at about 0.001-10 g and the corrosion inhibitor is benzazole.   18. The composition of claim 17, wherein the thickener and / or surfactant is included at about 1.0-5.0 g and the corrosion inhibitor is mercaptobenzoxazole.   18. The composition of claim 17, wherein the zinc compound is included in the aqueous solution in an amount of about 0.5-2.0 grams per liter of solution and the corrosion inhibitor is mercaptobenzazole.   The acidic aqueous solution includes at least one fluorometal compound selected from the group consisting of fluorotitanic acid, fluorotantalate, fluoroborate, fluorosilicate and mixtures thereof at about 0.01-12 g per liter. 18. The composition of claim 17, wherein the corrosion inhibitor is a mixture of corrosion inhibitors.   40. The composition of claim 38, wherein the fluorometal compound is tetrafluoroborate, the fluorozirconate is hexafluorozirconate, and the inhibitor is benzotriazole.   39. The composition of claim 38, wherein the fluorometal compound is hexafluorosilicate, the fluorozirconate is hexafluorozirconate, and the inhibitor is tolyltriazole.

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