KR101714292B1 - Methods for treating a ferrous metal substrate - Google Patents

Abstract

A method for treating and coating an iron metal base such as a cold-rolled steel sheet, a hot-rolled steel sheet and an electro-galvanized steel sheet is disclosed. The method comprises contacting an iron metal substrate with (a) Group IIIB and / or Group IVB metal compounds; (b) a phosphate ion; And (c) water. Also disclosed is an off-shift method for removing iron from the pretreatment bath.

Description

METHODS FOR TREATING A FERROUS METAL SUBSTRATE [0001]

The present invention relates to a method of treating an iron metal base such as a cold-rolled steel sheet, a hot-rolled steel sheet and an electro-galvanized steel sheet. The present invention also relates to coated iron metal substrates. The present invention also relates to a process for removing iron from a pretreatment bath when the pretreatment bath is on the process line in the presence of the article to be coated by the pretreatment composition and when the pretreatment bath is off-shifted.

Cross reference of related application

This application is related to U.S. Patent Application No. 12 / 237,770, filed September 25, 2008, which claims priority to U.S. Provisional Application No. 60 / 975,957, filed September 28, 2007, Which is a continuation-in-part of U.S. Patent Application No. 13 / 313,473, filed December 7, 2011, which is a continuation-in-part of U.S. Patent No. 8,097,093.

It is customary to use a protective coating on the metal substrate for improved corrosion resistance and paint adhesion. Conventional techniques for coating such substrates include techniques involving pretreating metal substrates with phosphate conversion coatings and chromium-containing rinses. Typical phosphate conversion coatings operate in the phosphate range above about 1,000 ppm, which results in waste disposal problems. Thus, the use of such phosphate and / or chromate-containing compositions results in environmental and health concerns.

Thus, a chromate-free and / or phosphate-free pretreatment composition has been developed. Such compositions generally are based on chemical mixtures that react in some manner with the substrate surface and bind to the surface to form a protective layer. For example, pretreatment compositions based on Group IIIB or Group IVB metal compounds have become more popular in recent years.

However, when treating an iron metal substrate through a pretreatment composition based on a Group IIIB or Group IVB metal compound, the concentration of trivalent iron (Fe ⁺³ ) in the bath of the pretreatment composition increases with time, It increases as the metal is treated. In particular, soluble (Fe ⁺² ) iron from the substrate becomes insoluble (Fe ⁺³ ) through accumulation of Fe ⁺² concentration, oxidation and subsequent reaction with oxygen and water. The resulting insoluble rust, that is, hydrated iron (III) oxide _{(Fe 2 O 3 · n H} 2 O) and / or iron (III) oxide-hydroxide (FeO (OH)) is aggregated such insoluble rust particles processing part Lt; / RTI > does not precipitate during the moderate agitation present in the < RTI ID = Thus, the insoluble green particles may be deposited or deposited on the substrate and transferred to a downstream electrocoating bath that is used in subsequent processing steps, particularly when the filtration device can not be used, for example when depositing organic coatings. This cross-contamination can adversely affect the performance of subsequent electrodeposition coatings.

It is therefore a common practice in the art to dilute the pretreatment bath periodically to reduce the concentration of soluble iron as a precautionary measure and to supplement the bath components and to restore the coating properties by adding the replenishing liquid to the pretreatment bath. In some cases, a pretreatment bath should be removed from the process line to remove rust therefrom. Alternatively, the pretreatment bath should be drained every 1 to 2 weeks and supplemented with fresh bath. Each of these methods is costly due to considerable loss of product, waste treatment and inconvenience.

Accordingly, it is desirable to provide an improved method for treating ferrous metal substrates and removing soluble iron that solves at least some of these problems.

In certain embodiments, the present invention relates to a method of coating an iron metal substrate.

In certain embodiments, a method of coating an iron-based substrate comprises: (A) contacting the iron-based substrate with a solution comprising (a) a Group IIIB and / or Group IVB metal compound; (b) a phosphate ion; And (c) water; And then (B) contacting the substrate with a coating composition comprising a film-forming resin to form a coated metal substrate exhibiting corrosion resistance characteristics, wherein the Group IIIB and / Wherein the weight ratio of Group IIIB and / or Group IVB metal to phosphate ions in the pretreatment composition is at least 0.8: 1, and wherein the phosphate ions are present in the pretreatment composition in an amount of about 500 ppm (Ii) insufficient to prevent deposition of a Group IIIB or Group IVB metal film having a coverage of at least 10 mg / m ² on the iron metal substrate, (iii) Is maintained in a bath of the pretreatment composition in an amount to produce a weight ratio of 1.8: 1 phosphate to trivalent iron ion.

In another specific embodiment, a method of coating an iron-based substrate comprises: (A) contacting an iron-based substrate with a solution of (a) a Group IIIB and / or Group IVB metal compound; (b) a phosphate ion; And (c) water; And then (B) contacting the substrate with a coating composition comprising a film-forming resin to form a coated metal substrate exhibiting corrosion resistance characteristics, wherein the Group IIIB and / Wherein the weight ratio of Group IIIB and / or Group IVB metal to phosphate ions in the pretreatment composition is at least 0.8: 1, and wherein the phosphate ions are present in the pretreatment composition in an amount of about 500 ppm (Ii) insufficient to prevent deposition of a Group IIIB or Group IVB metal film having a coverage of at least 10 mg / m < ² > on the ferrous metal substrate; (iii) 1.8 to 10: 1 Lt; RTI ID = 0.0 > of iron, < / RTI > in a phosphate-to-iron state.

In another specific embodiment, the present invention is directed to a method for removing iron from a pretreatment bath comprising the steps performed when the pretreatment bath is off-shifted.

In a particular embodiment, an off-shift method for removing iron from a pretreatment bath containing a pretreatment composition comprising a Group IIIB and / or Group IVB metal comprises: (a) reducing the pH of the pretreatment bath by at least 0.2; (b) adding a phosphate ion to the pretreatment bath of (a); And (c) raising the pH of the pretreatment bath of (b) by 0.2 or more.

In another particular embodiment, an off-shift method for removing iron from a pretreatment bath comprising a pretreatment composition comprising a Group IIIB and / or Group IVB metal comprises: (a) adding an acid to the pretreatment bath to reduce the pH of the pretreatment composition to below 4.0 ; (b) applying a phosphate ion to the pretreatment bath of (a); And (c) raising the pH of the pretreatment bath of (b) to 4.0 to 5.5.

The invention also relates to a substrate treated and coated by them.

1 and 2 are graphs of the observation results of Example 3. Fig.
3 is a graph of the observation result of Example 4. Fig.
4 is a graph of the observation result of Example 5. Fig.
5 is a graph of the observation result of Example 6. Fig.

It should be understood that, for the following detailed description, the present invention may take other various changes and steps, except where explicitly stated to the contrary. Moreover, it should be understood that, in addition to any embodiment or variant, all numbers expressing quantities of ingredients, for example, used in the specification and claims are to be understood as being modified in all instances by the term " about. &Quot; Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the properties sought to be obtained by the present invention. Each numerical parameter should at least be construed not to limit the application of the doctrine of equivalents to the scope of the claims, but to apply at least the ordinary rounding techniques in light of the number of reported significant digits.

Although the numerical ranges and parameters listing the broad scope of the invention are approximations, the numerical values listed in the specific embodiments are reported as precisely as possible. However, any numerical value inherently contains some error that inevitably arises from the standard deviation found in each test measurement.

Furthermore, any numerical range recited in the present invention is intended to include all sub-ranges included in these ranges. For example, a range of "1 to 10" would include all subranges having a minimum value between 1 (inclusive) and 10 (inclusive), i.e., a minimum value of 1 and a maximum value of 10 or less.

In this application, the use of the singular includes the plural and the plural includes the singular, unless specifically stated otherwise. Also, in this application, the use of "or" means "and / or" unless expressly specified otherwise, although "and / or"

As used herein, the term "off-shift" means that the article to be coated by the pretreatment composition is not in the pretreatment bath, but does not necessarily mean that the pretreatment bath must be removed from the process line.

As used herein, the term "total iron" or "total Fe" refers to the total amount of iron in the pretreatment bath, including, but not limited to, bivalent iron (Fe ⁺² ) and trivalent iron (Fe ⁺³ ).

As used herein, unless the precursor composition specifically refers to a pretreatment composition as being "substantially free" for a particular component, this means that the substance to be discussed, if any, is present in the composition as a minor impurity. That is, although these materials are not intentionally added to the composition, they may be present in minor or insignificant levels because they are carried as impurities as part of the intended composition components. Moreover, if the pretreatment composition is referred to as "totally free" with a particular ingredient, it means that the substance to be studied is not present in the composition at all.

As noted above, certain embodiments of the present invention are directed to methods of treating ferrous metal substrates. Ferrous metal substrates suitable for use in the present invention may be used in the manufacture of automotive bodies, automotive parts, and other components used frequently in the assembly of other articles, such as small metal parts including fasteners, such as nuts, bolts, screws, pins, nails, Buttons, and the like. Specific examples of suitable ferrous metal substrates include, but are not limited to, steels coated with cold-rolled steel, hot-rolled steel, zinc metal, zinc compounds or zinc alloys such as electroless zinc plated steel, molten zinc plated steel, Includes steel plated with alloys. Moreover, the metal substrate treated by the method of the present invention may be a cutting edge of the substrate onto which the remainder of the substrate surface is otherwise treated and / or coated. The coated ferrous metal substrate according to the method of the present invention may be in the form of, for example, a metal sheet or a manufactured part.

The ferrous metal substrate treated according to the method of the present invention may first be cleaned to remove grease, dust or other foreign matter. The cleaning is often carried out by using a mild or strong alkaline detergent, for example, a commercially available detergent conventionally used in metal pretreatment processes. Examples of alkaline detergents suitable for use in the present invention include Chemkleen (TM) 163, 177, 611L and 490MX, each of which is commercially available from PPG Industries Inc. . Such detergents are often carried out after water washing and / or preceded by said washing.

As noted above, certain embodiments of the present invention are directed to a method of treating a metal substrate comprising contacting the metal substrate with a pretreatment composition comprising Group IIIB and / or Group IVB metals. As used herein, the term " pretreatment composition "refers to a composition that reacts with the substrate surface upon contact with the substrate, chemically modifies the surface and combines with the surface to form a protective layer.

Often, the pretreatment composition comprises a carrier, often an aqueous medium, such that the composition can be in the form of a solution or dispersion of Group IIIB or Group IVB metal compounds in the carrier. In these embodiments, the solution or dispersion may be applied by any of a variety of known techniques, for example by dipping or impregnating, spraying, intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing or roll- . In certain embodiments, the solution or dispersion is present at a temperature in the range of 50 to 150 ° F (10 to 65 ° C) when applied to the metal substrate. The contact time is often from 2 seconds to 5 minutes, for example from 30 seconds to 2 minutes.

As used herein, the term " Group IIIB and / or IVB metal "refers to an element in Group IIIB or IVB of the Periodic Table of the Elements of Chemical Elements (for example, see Handbook of Chemistry and Physics, 63 ^rd edition )] Reference). If applicable, the metal itself may be used. In certain embodiments, Group IIIB and / or Group IVB metal compounds are used. As used herein, the term " Group IIIB and / or IVB metal compound "refers to a compound comprising at least one element in Group IIIB or Group IVB of the Periodic Table of the CAS Elements.

In certain embodiments, the Group IIIB and / or Group IVB metal compounds used in the pretreatment composition may be compounds of zirconium, titanium or hafnium, or mixtures thereof. Suitable zirconium compounds include, but are not limited to, hexafluorozirconic acid, alkali metals and ammonium salts thereof, ammonium zirconium carbonates, zirconium basic carbonates, zirconyl nitrates, zirconium carboxylates and zirconium hydroxycarboxylates such as hydrofluoro Zirconium acid, zirconium acetate, zirconium oxalate, ammonium zirconium glycolate, ammonium zirconium lactate, ammonium zirconium citrate, and mixtures thereof. Suitable titanium compounds include, but are not limited to, fluorotitanic acid and its salts. Suitable compounds of hafnium include, but are not limited to, hafnium nitrate.

In certain embodiments, the Group IIIB and / or Group IVB metal compounds are pre-treated with a metal of at least 10 ppm, such as at least 20 ppm metal, at least 30 ppm metal, or in some cases at least 50 ppm metal (measured as metal element) Is present in the bath of the composition. In certain embodiments, the Group IIIB and / or Group IVB metal compounds are selected from the group consisting of less than 500 ppm of metal, e.g., less than 150 ppm of metal, or in some cases less than 80 ppm of metal (measured as metal element) It exists in the bath. The amount of Group IIIB and / or IVB metal in the pretreatment composition may range between any combination of the recited values, including the recited values.

As noted above, the pretreatment composition used in certain embodiments of the method of the present invention comprises phosphate ions. In certain embodiments, the source of the phosphate ion is phosphoric acid, e.g., 75% phosphoric acid, although other sources of phosphate ions such as monosodium phosphate or disodium phosphate may also be considered in the present invention. In another particular embodiment, the pretreatment composition of the present method is substantially free of phosphate ions.

As noted above, in certain embodiments of the methods of the present invention, the phosphate ions are maintained in a bath of the pretreatment composition in an amount sufficient to substantially prevent the formation of bath-insoluble rust. As used herein, the term "retained " means to adjust the amount of phosphate ion and, if necessary, to essentially prevent the formation of insoluble rust. The phrase "preventing the formation of essentially insoluble rust" as used herein means insoluble rust, i.e., non-limitingly, hydrated iron (III) oxide (Fe ₂ O ₃ .nH ₂ O) and / or iron ) Oxide-hydroxide (FeO (OH) 2) is prevented from forming in the bath to such an extent that the orange or reddish brown appearance, which indicates the formation of such compounds in the bath, is not visible to the naked eye. Rather, in certain embodiments of the present invention, the phosphate ion is added to the bath in an amount sufficient to form a complex with the etched iron from the surface of the ferrous metal substrate treated to form iron (III) phosphate (FePO ₄ ) Which forms a bath with a more opaque appearance than the orange or reddish brown appearance associated with the presence of iron and leads to the formation of insoluble sludge which can be removed from the bath using conventional filtration equipment. Accordingly, certain embodiments of the present invention are directed to a process for the formation of an insoluble rust in a bath which is deposited on a substrate and which can be transferred to a subsequent processing apparatus, for example a top-down spray nozzle, a pump, a cleaning bath and an electrolytic coating bath, (Fe < ^{+ 3} >). As noted above, this cross-contamination can adversely affect the performance of subsequent deposited coatings.

In certain embodiments of the method of the present invention, phosphate ions may also have a coverage rate of greater than 10 mg / m ^2, for example greater than 100 mg / m ^2, or, in some cases, greater than 100 to 500 mg / m ^2, Lt; RTI ID = 0.0 > IIIB < / RTI > or < RTI ID = 0.0 > IVB < / RTI > Especially at the pH of the bath used in the present invention, to prevent deposition of sufficient IIIB or IVB metal film between the phosphate ions that form complexes with the soluble iron precipitated from the ferrous metal substrate and on the ferrous metal substrate, It has been found that there is a subtle balance between the phosphate ions that form complexes with Group IIIB or Group IVB metals present in undesirable baths.

The presence of from 1 to 1.8, for example 1.2 to 1.6, parts by weight of a phosphate ion for 1 part by weight of trivalent iron (Fe ⁺³ ) ions in the composition essentially prevents On the other hand, is insufficient to prevent deposition of a Group IIIB or Group IVB metal film having a coverage of greater than 100 mg / m ^2, for example, greater than 10 mg / m ² . Thus, in certain embodiments of the method of the present invention, the phosphate ion is maintained in the bath at a level that results in a weight ratio of phosphate ion to trivalent iron ion of from 1 to 1.8: 1, in some cases from 1.2 to 1.6: 1. If the weight ratio of phosphate ion to trivalent iron ion is less than 1: 1, the phosphate in the bath is too small to essentially prevent the formation of insoluble rust in the bath as described above. If the weight ratio of phosphate ion to trivalent iron ion exceeds 1.8: 1, the amount of phosphate ion may be sufficient to prevent deposition of a suitable Group IIIB or IVB metal film on the iron metal substrate. The ratio of phosphate ions to trivalent iron ions in the pretreatment composition may range between any combination of the recited values including the recited values.

Also, in certain embodiments of the methods of the invention, the phosphate ions are at least 50: 1, in some cases at least 25: 1, in some cases 12.5: 1, in some cases at least 3: 1, in some cases at least 2: Lt; RTI ID = 0.0 > IIIB < / RTI > and / or IVB metal to phosphate ions in the bath. If the weight ratio of Group IIIB and / or Group IVB metal to phosphate ions is less than 2: 1, the bath may have too much phosphate, which may have a negative impact on the ability to deposit sufficient Group IIIB or Group IVB metal films on the ferrous metal substrate .

As is evident, the pretreatment compositions of the present invention comprise in some cases from 20 to 500 ppm Group IIIB and / or Group IVB metals, for example from 30 to 150 ppm, Group IIIB and / or Group IVB metals, in some cases from 30 to 80 ppm In certain embodiments of the methods of the present invention, relatively few phosphate ions are often present in the bath, because in certain embodiments the phosphate ions are present in the bath at least 2: 1 , In some cases at least at a level of 3: 1, resulting in a weight ratio of Group IIIB and / or Group IVB metal to phosphate ions in the bath. However, the presence of a small level of phosphate ion has been found to provide a dramatic effect on bath life by preventing the formation of insoluble rust in the pretreatment bath, for example in certain embodiments up to several months or years, for example by removing iron from the pretreatment bath.

As described above, when treating an iron metal substrate through a pretreatment composition based on a Group IIIB or Group IVB metal compound, the concentration of the trivalent iron (Fe ⁺³ ) in the bath of the pretreatment composition is greater than that of the iron- As the processing proceeds, it increases with time. The result is the accumulation of insoluble rust that can be deposited on the substrate to process such bath and carry it to a subsequent processing step. To prevent this, these baths should be replaced periodically, in some cases once a week. Surprisingly, however, it has been found that the presence of a small level of phosphate can work for several months, perhaps indefinitely, without preventing the formation of insoluble rust, without preventing the formation of Group IIIB and / or IVB metal films . It was surprising and unpredictable that these small levels of phosphate could extend bath life considerably. In addition, the presence of such small amounts of phosphate ions leads to the formation of a minimum amount of sludge than can be counteracted by insoluble rust prevention, thereby avoiding waste treatment problems.

In certain embodiments, the pretreatment composition also comprises an electropositive metal. The term " electropositive metal "as used herein refers to a metal that is more electropositive than the metal substrate. This means that for the purposes of the present invention, the term " electropositive metal "includes metals which are less easily oxidized than the metal-based metal being treated. As will be appreciated by those skilled in the art, the tendency of metals to be oxidized is referred to as oxidation potential and is expressed as a bolt and measured against a standard hydrogen electrode (which is randomly assigned with an oxidation potential of zero). The oxidation potentials of the various elements are shown in the following table. An element is less easily oxidized than another element if the element has a voltage value E ^* that is greater than the element compared to the element in the table below.

Thus, as is evident, when the metal substrate comprises a ferrous metal, as in the present case, the electropositive metals suitable for inclusion in the pretreatment composition include, for example, nickel, tin, copper, ≪ / RTI >

In certain embodiments, the source of the electropositive metal in the pretreatment composition is a water soluble metal salt. In certain embodiments of the present invention, the water soluble metal salt is a water soluble copper compound. Specific examples of water-soluble copper compounds suitable for use in the present invention include, but are not limited to, copper cyanide, copper potassium cyanide, copper sulfate, copper nitrate, copper pyrophosphate, copper thiocyanate, Copper acetate, copper propionate, copper acetate, copper propionate, copper acetate, copper propionate, copper acetate, copper propionate, copper tetrachloride, Copper sulfate, copper sulfate, copper sulfate, copper sulfate, copper sulfate, copper sulfate, copper sulfate, copper sulfate, Copper glutamate, copper fumarate, Copper salts of carboxylic acids of formic acid to decanoic acid series as well as copper salts of polybasic acids of oxalic acid to suberic acid series, and glycols such as glycols, such as glyceryl phosphate, sodium copper chlorophyllin, copper fluorosilicate, copper fluoroborate and copper iodate, Include copper salts of hydroxycarboxylic acids including acids, lactic acid, tartaric acid, malic acid and citric acid.

When a copper ion supplied from such a water-soluble copper compound is precipitated as an impurity in the form of copper sulfate or copper oxide, a complexing agent is added which suppresses the precipitation of copper ions and stabilizes the ions as a copper complex in the solution May be preferred.

In certain embodiments, the copper compound is added as a copper complex salt such as K ₃ Cu (CN) ₄ or Cu-EDTA, and the salt may exist solely in the composition stably, It is also possible to form a copper complex which can stably exist in the pretreatment composition by bonding with a complexing agent. Examples include copper cyanide complexes formed by a combination of CuCN and KCN or a combination of CuSCN and KSCN or KCN, and Cu-EDTA complex formed by a combination of CuSO ₄ and EDTA · 2Na.

With respect to the complexing agent, a compound capable of forming a complex with the copper ion can be used; Examples thereof include polyphosphates such as sodium tri-polyphosphate and hexametaphosphoic acid; Aminocarboxylic acids such as ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid and nitrilotriacetic acid; Hydroxycarboxylic acids such as tartaric acid, citric acid, gluconic acid and salts thereof; Aminoalcohols such as triethanolamine; Sulfur compounds such as thioglycolic acid and thiourea, and phosphonic acids such as nitrilotrimethylenephosphonic acid, ethylenediaminetetra (methylenephosphonic acid), and hydroxyethylidenediphosphonic acid.

In certain embodiments, the electropositive metal, for example copper, is included in the pretreatment composition in an amount of at least 1 ppm, for example at least 5 ppm, or in some cases at least 10 ppm total metal (measured as elemental metal). In certain embodiments, the electropositive metal is included in the pretreatment composition in an amount of less than 500 ppm, e.g., less than 100 ppm, or in some cases less than 50 ppm, total metal (measured as elemental metal). The amount of electropositive metal in the pretreatment composition may range between any combination of the recited values, including the recited values.

As described, the working pH of the pretreatment composition used in the process of the present invention ranges from 4.0 to 5.5, in some cases from 4.0 to 5.0, from 4.5 to 5.5, or in other cases from 4.5 to 5.0. The pH of the pretreatment composition can be adjusted, for example, using any necessary acid or base.

In addition to the foregoing components, the pretreatment composition used in the method of the present invention may comprise any of a variety of additional components. For example, in certain embodiments, the pretreatment composition used in the method of the present invention may be prepared by reacting a polyfunctional cyclic compound such as described in U.S. Patent No. 6,805,756, column 3, line 9 to column 4, line 32, ≪ / RTI > However, in other embodiments, the pretreatment composition used in the method of the present invention is substantially free or, in some cases, completely free of any such polyfunctional cyclic compound.

In certain embodiments, the pretreatment composition used in the methods of the present invention may be prepared, for example, as described in U.S. Patent No. 6,805,756, column 4, line 52 to column 5, line 13, and US Patent No. 6,193, Line to column 5, line 39. < tb > < TABLE > In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such oxidizer-promoter.

In certain embodiments, the pretreatment composition comprises an organic film-forming resin, such as reaction products of an alkanolamine and an epoxy-functional material containing two or more epoxy groups, e.g., those disclosed in U.S. Patent No. 5,653,823; Resins containing beta hydroxy esters, imides or sulfide functionalities incorporated with dimethylol propionic acid, phthalimide, or mercaptoglycerin as additional reactants in the manufacture of resins; The reaction product is a mixture of diglycidyl ether, dimethylol propionic acid and diethanolamine of bisphenol A (commercially available as EPON 880 from Shell Chemical Company) of 0.6 to 5.0: 0.05 to 5.5: 1; Water-soluble and water-dispersible polyacrylic acids as disclosed in U.S. Patent No. 3,912,548 and U.S. Patent No. 5,328,525; Phenol formaldehyde resins as disclosed in U.S. Patent No. 5,662,746; Water-soluble polyamides such as those disclosed in WO 95/33869; Copolymers of maleic acid or acrylic acid with allyl ethers as disclosed in Canadian Patent Application No. 2,087,352; And water-soluble and dispersible resins including epoxy resins, aminoplasts, phenol-formaldehyde resins, tannins and polyvinylphenols as discussed in U.S. Patent No. 5,449,415. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any organic film-forming resin, such as one or more of the foregoing.

In certain embodiments, the pretreatment composition used in the method of the present invention comprises a fluoride ion as described in US Patent 6,805,756, column 6, lines 7-23, which is incorporated herein by reference. In certain embodiments, the fluoride ion is introduced into the composition through Group IIIB and / or Group IVB metal compounds. In certain embodiments, the pretreatment composition is substantially free or, in some cases, free of any fluoride ions introduced into the pretreatment composition from sources other than those through Group IIIB and / or Group IVB metal compounds.

In certain embodiments, the pretreatment composition used in the methods of the present invention may be prepared as described in U.S. Patent No. 6,805,756, Column 6, lines 53 to 64, and International Application WO 2005/001158, page 3, lines 17-23 And the like polysaccharides. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such polysaccharide.

In certain embodiments, the pretreatment composition used in the method of the present invention may be a phosphate acid ester as described in US Patent 5,139,586, column 6, lines 31 to 63, incorporated herein by reference, a water soluble polyethylene glycol ester of fatty acid and / Nitric acid. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any of these phosphate acid esters, water soluble polyethylene glycol esters of fatty acids and / or nitric acid.

In certain embodiments, the pretreatment composition used in the method of the present invention comprises vanadium and / or cerium ions as described in US Patent 4,992,115, column 2, line 47 to column 3, line 29, . In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such vanadium and / or cerium ions.

In certain embodiments, the pretreatment composition used in the method of the present invention comprises a phosphorous acid, a hypophosphoric acid, and / or a salt thereof, as described in US Patent 5,728, 233, column 4, lines 24 to 37, . In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any of these phosphorous acids, hypophosphorous acids and / or salts thereof.

In certain embodiments, the pretreatment compositions used in the methods of the present invention may be prepared from a Group IIA metal as described in U.S. Patent No. 5,380,374 at column 3, lines 25 to 33 and / or the United States of America Include Group IA metals as described in Patent No. 5,441,580 column 2, line 66 to column 3, line 4. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such Group IIA metal and / or Group IA metal.

In certain embodiments, the pretreatment composition used in the process of the present invention comprises a molybdenum compound as described in British Patent Application GB 2 259 920 A, which is incorporated herein by reference. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such molybdenum compound.

In certain embodiments, the pretreatment composition used in the method of the present invention may be a scandium, yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, At least one ion of a metal selected from the group consisting of molybdenum, holmium, erbium, thulium, ytterbium, and lutetium. In contrast, in another embodiment, the pretreatment composition comprises one or more ions of a metal selected from the group consisting of scandium, yttrium, lanthanum, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, Or, in some cases, none at all.

The pretreatment composition may optionally contain other materials such as non-ionic surfactants and adjuvants conventionally used in the pretreatment field. Among aqueous media, water-dispersible organic solvents such as alcohols having about 8 carbon atoms or less, such as methanol, isopropanol, etc., are present; Or glycol ethers such as ethylene glycol, diethylene glycol, or monoalkyl ethers of propylene glycol, and the like. When present, the water-dispersible organic solvent is typically used in an amount up to about 10% by volume based on the total volume of the aqueous medium.

Other optional materials include surfactants that act as defoamers or substrate wetting agents.

In certain embodiments, the pretreatment composition also comprises a filler such as a siliceous filler. Non-limiting examples of suitable fillers include silica, mica, montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, vermiculite, vermiculite, natural and synthetic zeolite, cement, calcium silicate, aluminum silicate, sodium aluminum silicate, aluminum polysilicate, And glass particles. Substantially insoluble fillers on other finely divided particles other than the siliceous filler may also be used. Examples of such optional fillers include carbon black, charcoal, graphite, titanium oxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconia, magnesia, alumina, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, Magnesium. In contrast, in another embodiment, the pretreatment composition is substantially free or, in some cases, completely free of any such filler.

In certain embodiments, the pretreatment composition is substantially free or, in some cases, totally free of chromates and / or heavy metal phosphates such as zinc phosphate. As used herein, the term " substantially free " when used in connection with the absence of chromates and / or heavy metal phosphates in the pretreatment composition means that these substances are not present in the composition to the extent that they cause an environmental burden. As used herein, the term " absolutely free " when used in connection with the absence of chromate and / or heavy metal phosphate means that there is no chromate and / or heavy metal phosphate in the composition at all.

As is known, in certain embodiments, the pretreatment composition used in the process of the present invention comprises (a) Group IIIB and / or Group IVB metal compounds such as zirconium compounds; (b) a source of phosphate ions such as phosphoric acid; And (c) consists essentially of, or in some cases consists of, water. In another specific embodiment, the pretreatment composition used in the process of the present invention comprises (a) Group IIIB and / or Group IVB metal compounds such as zirconium compounds; And (c) consists essentially of, or in some cases consists of, water. In certain embodiments, such pretreatment compositions comprise fluoride ions that are introduced into the pretreatment composition through Group IIIB and / or Group IVB metal compounds. As used herein, the phrase "consisting essentially of " means that the composition is substantially free of other components that may affect the basic and novel property (s) of the present invention. For purposes of the present invention, This means that it does not include any components that substantially affect the ability of the pretreatment composition to be successfully used in the method of the present invention.

In certain embodiments, the film coverage rate (total film weight) of the residue of the pretreatment coating composition is greater than or equal to 10 mg / m 2, such as from 100 to 500 mg / m 2 or, in some cases, greater than or equal to 50 mg / m 2. Though the thickness of the pretreatment coating can vary, it is generally very thin, often less than 1 μm, in some cases 1 to 500 nm, and in other cases 10 to 300 nm, for example 20 to 100 nm.

In certain embodiments, the off-shift method is used to remove the soluble iron in the pretreatment bath so that the pretreatment bath is substantially free of iron at the completion of the off-shift process so that insoluble rust in the working bath of the pretreatment composition is essentially . As used herein, the term " substantially free " when used for the working bath of the pretreatment composition means that the total amount of iron is present in an amount of less than 10 ppm. As described herein, in certain embodiments, the bath of the pretreatment composition is substantially free of phosphate ions, for example, in a pretreatment system, during operation of the bath, wherein the presence of phosphate in the pretreatment bath, Can adversely affect the deposition of the composition. In such embodiments, the off-shift method of removing iron from the pretreatment bath can be particularly useful in such a pretreatment system that is essentially free of phosphate ions as a method of preventing the formation of insoluble rust in the pretreatment bath. Also, as described herein, in another particular embodiment, the bath of pretreatment composition essentially comprises phosphate ions as a method of preventing the formation of insoluble rust in the pretreatment bath. In such embodiments, the off-shift method of removing iron from the pretreatment bath may be particularly useful as an additional or secondary method of preventing the formation of insoluble rust in the pretreatment bath.

As noted above, in certain embodiments, the pretreatment bath has an operating pH of greater than 4.0, e.g., 4.2 to 5.5, preferably 4.5 to 5.0, and most preferably 4.8. In certain embodiments, the first step of the off-shift method of removing iron from the pretreatment bath is to reduce the pH of the pretreatment bath to at least 0.2, e.g., at least 0.5 or at least 1.0, such that the pH of the pretreatment bath is between 1.0 and 3.8, 2.5 to 3.3. In certain embodiments, the pH of the pretreatment bath is, as a non-limiting example, an acid including a Group IVB fluorometallic acid such as hexafluorozirconic acid and hexafluorotitanic acid, phosphoric acid, sulfuric acid, sulfamic acid, nitric acid, Is reduced by adding it to the pretreatment bath.

In certain embodiments of the off-shift method of removing iron from the pretreatment bath, the first step of reducing the pH of the pretreatment bath is accomplished by adding a sufficient amount of acid to the pretreatment bath to reduce the pH discussed above.

In certain embodiments of the off-shift method of removing iron from the pretreatment bath, the second step involves adding phosphate ions to the pretreatment bath. In certain embodiments, the source of the phosphate ion may be an alkali metal and ammonium orthophosphate which is present as a monohydrogen or in the form of hydrogen, including monosodium phosphate, disodium phosphate and mixtures thereof, for example. In certain embodiments, Zircobond Additive P, a monosodium phosphate solution commercially available from Pfizer Industries, Inc. of Euclid, Ohio, is used as a source of phosphate ions.

In a particular embodiment of the off-shift method of removing iron from the pretreatment bath, the third step involves adding an oxidizing agent to the pretreatment bath. In such embodiments, the oxidizing agent is a peroxide compound, air, sodium nitrite, sodium bromate, and mixtures thereof. In a preferred embodiment, the peroxide compound is hydrogen peroxide.

In certain embodiments of the off-shift method of removing iron from the pretreatment bath, the source of phosphate ions and the oxidant are each added in an amount sufficient to produce a pretreatment bath that is substantially free of iron.

In a specific embodiment of the off-shift method of removing iron from the pretreatment bath, the fourth step involves raising the pH of the pretreatment bath by at least 0.2. In an embodiment, the pH rises above 4.0, e.g., 4.2 to 5.2, 4.5 to 5.0, and 4.8. In certain embodiments, the pH is elevated by adding a sufficient amount of an alkaline composition to the pretreatment bath, such as caustic soda, caustic potassium, and sodium hydroxide as non-limiting examples. In an embodiment, the alkaline composition is Chemfil Buffer, available from Pfizer Industries, Inc. of Euclid, Ohio, which can be used in an amount sufficient to achieve the desired operating pH.

In certain embodiments of the off-shifting process of the present invention, the phosphate ion is in an amount sufficient to form a complex with the etched iron from the surface of the ferrous metal substrate treated to form iron (III) phosphate (FePO ₄ ) , Which forms a bath with a more opaque appearance than the orange or reddish brown appearance associated with the presence of iron and results in the formation of insoluble sludge which can be removed from the bath using conventional filtration equipment. In a particular embodiment of the off-shift method of the present invention, the fifth step is to remove the solid material from the pretreatment bath, i. E. Iron phosphate, iron oxide, iron hydroxide or any other insoluble sludge formed in the pretreatment bath, To filter the pretreatment bath. In certain embodiments, the filtration step may be performed immediately after raising the pH of the pretreatment bath by at least 0.2. In another specific embodiment, the filtration step may be performed with an equilibration period during which the insoluble sludge may be precipitated at the base of the pretreatment bath, for example, 1 to 10 hours after the pH of the pretreatment bath is raised.

Thus, the off-shifting process of the present invention can be applied to a substrate that is deposited on a substrate and transferred to a subsequent processing apparatus such as a top-down spray nozzle, a pump, a cleaning bath and an electrolytic coating bath to form an insoluble rust Soluble iron (Fe < ^{+ 3} >) in the bath). As noted above, this cross-contamination can adversely affect the performance of subsequent deposited coatings. Surprisingly, however, it is possible to essentially remove the iron from the bath by lowering the pH of the pretreatment bath below the working pH and subsequently adding the said low levels of phosphate and optionally an oxidizing agent, whereby the pH of the bath rises to the operating level And subsequently prevented the formation of insoluble rust in the pretreatment bath without preventing the formation of suitable IIIB and / or IVB metal films, allowing the bath to be operated for months, perhaps indefinitely, without replacement. It was surprising and unexpected that these steps could extend the bath life considerably.

After contacting with the pretreatment solution, the substrate may be washed with water and dried.

In certain embodiments of the method of the present invention, after contacting the substrate with the pretreatment composition, the substrate is then contacted with a coating composition comprising a film-forming resin. The substrate may be contacted with such a coating composition using any suitable technique such as, for example, brushing, dipping, flow coating, spraying, and the like. However, in certain embodiments, as described in more detail below, such contact includes an electrocoating step of depositing the electrodepositable composition on the metal substrate by electrodeposition.

The term "film-forming resin" as used herein refers to a resin capable of forming a self-sustaining continuous film upon removal of any diluent or carrier present in the composition, or at least on the horizontal surface of the substrate upon curing at ambient or elevated temperatures Quot; Conventional film-forming resins that may be used include, but are not limited to, automotive OEM coating compositions, automotive retouch coating compositions, industrial coating compositions, architectural coating compositions, coil coating compositions, and aerospace coating compositions, among others Including those used.

In certain embodiments, the coating composition comprises a thermosetting film-forming resin. The term "thermosetting " as used herein refers to a resin that is" cured "irreversibly upon curing or crosslinking, wherein the polymer chains of the polymer components are bonded together by covalent bonds. This property is usually associated with cross-linking reactions of the components of the composition, which are often caused, for example, by heat or irradiation. The curing or crosslinking reaction may also be carried out under ambient conditions. Once cured or crosslinked, the thermosetting resin will not melt upon application of heat and is insoluble in the solvent. In another embodiment, the coating composition comprises a thermoplastic film-forming resin. As used herein, the term "thermoplastic" refers to a resin that is not bonded by covalent bonds and thereby experiences polymeric components that are susceptible to liquid flow upon heating and that are soluble in the solvent.

As indicated above, in certain embodiments, the substrate is contacted with a coating composition comprising a film-forming resin by an electrocoating step wherein the electrodepositable composition is deposited onto the metal substrate by electrodeposition. In the electrodeposition process, the treated metal substrate and the electrically conductive counter electrode, acting as electrodes, are placed in contact with the ionic, electrodepositable composition. Upon passing an electric current between them while the electrode and the counter electrode remain in contact with the electrodepositable composition, the adherent film of the electrodepositable composition will be deposited on the metallic substrate in a substantially continuous manner.

Electrodeposition is usually carried out at a constant voltage ranging from 1 volt to several thousand volts, typically in the range of 50 to 500 volts. The current density is usually from 1.0 amperes to 15 amps / m < ² > (10.8 to 161.5 amps / m < ² >) and tends to decrease rapidly during the electrodeposition process, indicating the formation of a continuous self-insulating film.

The electrodepositable composition used in certain embodiments of the present invention comprises a resinous phase, often dispersed in an aqueous medium, wherein the dendritic resin comprises (a) an active hydrogen group-containing ionic electrodepositable resin and (b) And a curing agent having a functional group that is reactive with the active hydrogen group of the curing agent.

In certain embodiments, the electrodepositable compositions used in certain embodiments of the present invention are primary film-forming polymers and contain active hydrogen-containing ionic, often cationic, electrodepositable resins. A wide variety of electrodepositable film-forming resins are known and can be used in the present invention as long as they are suitable to be "water dispersible ", i.e., soluble, dispersed or emulsified in water. The water dispersible polymer is substantially ionic, i.e. the polymer will contain anionic functional groups to impart a negative charge, or often will contain cationic functional groups to impart a positive charge.

Examples of film-forming resins suitable for use in anionic electrodepositable compositions include base-dissolved carboxylic acid-containing polymers such as the reaction product or adduct of a dry oil or semi-dry fatty acid ester with a dicarboxylic acid or anhydride; And reaction products of fatty acid esters, unsaturated acids or anhydrides with any further unsaturated modified materials (further reacted with polyols). Also suitable are at least partially neutralized copolymers of hydroxy-alkyl esters of unsaturated carboxylic acids, unsaturated carboxylic acids and one or more other ethylenically unsaturated monomers. Yet another suitable electrodepositable film-forming resin comprises an alkyd-aminoplast vehicle, i.e., a vehicle containing an alkyd resin and an amine-aldehyde resin. Still another anionic electrodepositable resin composition comprises a mixed ester of a resinous polyol, for example, an ester as disclosed in U.S. Patent No. 3,749,657, column 9, lines 1 to 75 and column 10, lines 1 to 13, The above-cited portions are incorporated herein by reference. Other acid functional polymers such as phosphated polyepoxide or phosphated acrylic polymers as known to those skilled in the art can also be used.

As described above, it is often desirable that the active hydrogen-containing ionic electrodepositable resin (a) is cationic and capable of being deposited on a cathode. Examples of such cationic film-forming resins include amine salt group-containing resins such as acid-solubilized reaction products of polyepoxides and primary or secondary amines such as those described in U.S. Patent No. 3,663,389; U.S. Patent No. 3,984,299; U.S. Patent No. 3,947,338; And U.S. Patent No. 3,947,339. Often, these amine salt group-containing resins are used with blocked isocyanate curing agents. The isocyanate may be completely blocked as disclosed in U.S. Patent No. 3,984,299, or the isocyanate may be partially blocked and reacted with the resin backbone as disclosed in U.S. Patent No. 3,947,338. Also, one-component compositions as disclosed in U.S. Pat. No. 4,134,866 and DE-OS No. 2,707,405 can be used as film-forming resins. In addition to the above epoxy-amine reaction products, film-forming resins may also be selected from cationic acrylic resins such as those disclosed in U.S. Patent Nos. 3,455,806 and 3,928,157.

In addition to the amine salt group-containing resin, quaternary ammonium salt group-containing resins such as those described in U.S. Patent No. 3,962,165; 3,975,346; And the tertiary amine salts as disclosed in U.S. Patent No. 4,001,101 can also be used. Examples of other cationic resins are ternary sulfonium salt group-containing resins and quaternary phosphonium salt group-containing resins such as those disclosed in U.S. Patent No. 3,793,278 and U.S. Patent No. 3,984,922, respectively. In addition, film-forming resins that cure through transesterification can be used, for example those disclosed in European Application No. 12463. [ Furthermore, cationic compositions prepared from Mannich bases, such as those disclosed in U.S. Patent No. 4,134,932, can be used.

In certain embodiments, the resin present in the electrodepositable composition is a positively charged resin containing primary and / or secondary amine groups, for example, U.S. Patent No. 3,663,389; U.S. Patent No. 3,947,339; And U.S. Patent No. 4,116,900. In U.S. Pat. No. 3,947,339, polyamines, such as polyethylenetriamine or triethylenetetramine, are reacted with the polyepoxide. When the reaction product is neutralized with an acid and dispersed in water, a free primary amine group is generated. Also, as disclosed in U.S. Patent No. 3,663,389 and U.S. Patent No. 4,116,900, polyepoxides are reacted with excess polyamines such as diethylenetriamine and triethylenetetramine and excess polyamines are removed from the reaction mixture When vacuum stripping is performed, an equivalent amount of product is formed.

In certain embodiments, the active hydrogen-containing ionic electrodepositable resin is present in the electrodepositable composition in an amount of from 1 to 60% by weight, for example from 5 to 25% by weight, based on the total weight of the electrodeposition bath.

As shown, the resinous phase of the electrodepositable composition further comprises a curing agent which is often suitable to react with the active hydrogen groups of the ionic electrodepositable resin. For example, both blocked organic polyisocyanates and aminoplast curing agents are suitable for use in the present invention, but blocked isocyanates are often preferred for cathode electrodeposition.

Aminoplast resins, which are often preferred curing agents for anionic deposition, are condensation products of amines or amides with aldehydes. Examples of suitable amines or amides are melamine, benzoguanamine, urea and similar compounds. Generally, the aldehyde used can be prepared from formaldehyde, or from other aldehydes such as acetaldehyde and furfural. The condensation product contains a methylol group or similar alkylol group depending on the particular aldehyde used. Often these methylol groups are etherified by reaction with alcohols such as monohydric alcohols having 1 to 4 carbon atoms, such as methanol, ethanol, isopropanol and n-butanol. The aminoplast resin is commercially available from American Cyanamid Co. under the trade designation CYMEL and from Monsanto Chemical Co. under the trade designation RESIMENE.

The aminoplast hardener is often used together with the active hydrogen-containing anionic electrodepositable resin in an amount of a percentage ranging from 5 to 60% by weight, for example from 20 to 40% by weight, based on the total weight of the resin solids in the electrodepositable composition .

As shown, the blocked organic polyisocyanate is often used as a curing agent in a cathode electrodeposition composition. The polyisocyanate may be completely blocked as disclosed in U.S. Patent No. 3,984,299, column 1, lines 1-68, column 2 and column 3, lines 1 to 15, or alternatively, as disclosed in U.S. Patent No. 3,947,338, column 2, , Column 3 and column 4, lines 1 to 30, and the above recited moieties are incorporated herein by reference. "Blocked" means that the isocyanate group is reacted with the compound such that the resulting blocked isocyanate group is stable to active hydrogen at ambient temperature, but is usually reactive with active hydrogen in the film-forming polymer at a high temperature of 90 ° C to 200 ° C .

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates including alicyclic polyisocyanates, typical examples being diphenylmethane-4,4'-diisocyanate (MDI), 2,4- or 2,6-toluene diisocyanate (TDI) (including mixtures thereof), p-phenylene diisocyanate, tetramethylene and hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, phenylmethane- 4'-diisocyanate and a mixture of polymethylene polyphenyl isocyanate. More advanced polyisocyanates such as triisocyanates can be used. For example, neopentyl glycol and trimethylol propane, and polymeric polyols such as, for example, polycaprolactone diols and triols, such as < RTI ID = 0.0 & (Greater than 1 equivalent of NCO / OH equivalent ratio) may also be used.

The polyisocyanate curing agent is typically added together with the active hydrogen-containing cationic electrodepositable resin in an amount of from 5 to 60% by weight, for example from 20 to 50% by weight, based on the total weight of the resin solids in the electrodepositable composition Use in percentages.

In certain embodiments, the coating composition comprising the film-forming resin also comprises yttrium. In certain embodiments, yttrium is present in an amount of from 10 to 10,000 ppm, for example less than 5,000 ppm, and in some cases less than 1,000 ppm of total yttrium (measured as yttrium element) in such compositions. Both soluble and insoluble yttrium compounds can act as a source of yttrium. Examples of yttrium sources suitable for use in lead-free electrodepositable coating compositions are soluble organic and inorganic yttrium salts such as yttrium acetate, yttrium chloride, yttrium carbonate, yttrium sulfate, yttrium lactate, and yttrium nitrate. When yttrium is to be added as an aqueous solution to an electrocoating bath, yttrium nitrate, a readily available yttrium compound, is the preferred yttrium source. Other yttrium compounds suitable for use in electrodepositable compositions are organic and inorganic yttrium compounds such as yttrium oxide, yttrium bromide, yttrium hydroxide, yttrium molybdate, yttrium sulfate, yttrium silicate, and yttrium oxalate. Organic yttrium complexes and yttrium metals may also be used. When yttrium is to be incorporated into the electrocoating bath as a component in the pigment paste, yttrium oxide is often the preferred source of yttrium.

The electrodepositable composition disclosed in the present invention is in the form of an aqueous dispersion. The term "dispersion" is considered to be a two-phase transparent, translucent or opaque resinous system in which the resin is in a dispersed phase and water is in a continuous phase. The average particle size of the resin is generally less than 1.0 and usually less than 0.5 mu m, often less than 0.15 mu m.

The concentration of the dendritic phase in the aqueous medium is often at least 1% by weight, for example from 2 to 60% by weight, based on the total weight of the aqueous dispersion. When such a composition is in the form of a resin concentrate, the composition generally has a resin solids content of from 20 to 60% by weight, based on the weight of the aqueous dispersion.

The electrodepositable compositions disclosed in the present invention are often supplied as two components: (1) generally an active hydrogen-containing ionic electrodepositable resin, i.e., a main film-forming polymer, a curing agent, and any additional water- A clear resin feed comprising the components; And (2) a pigment paste, generally comprising one or more pigments (described below), a water dispersible resin that may be the same as or different from the main film-forming polymer, and optionally additives such as wetting or dispersing aids.

In certain embodiments, the two-component electrodepositable composition is implemented in the form of an electrodeposition bath, as is well known to those skilled in the art, where components (1) and (2) Dispersed in the medium. An advantage of the method of the present invention is that, as indicated above, it is possible to prevent the bath from being contaminated by rust even in the absence of a filtration device.

As described above, the aqueous medium may contain, in addition to water, a fusing solvent. Useful fusion solvents are often hydrocarbons, alcohols, esters, ethers, and ketones. Preferred fusion solvents are often alcohols, polyols and ketones. Specific fusion solvents include isopropanol, butanol, 2-ethylhexanol, isophorone, 2-methoxypentanone, ethylene and propylene glycol, and monoethyl monobutyl and monohexyl ether of ethylene glycol. The amount of the fusion solvent is generally from 0.01 to 25% by weight, for example from 0.05 to 5% by weight, based on the total weight of the aqueous medium.

In addition, colorants, and, if desired, various additives such as surfactants, wetting agents or catalysts may be included in the coating composition comprising the film-forming resin. As used herein, the term "colorant" means any material that imparts color and / or other opacity and / or other visual effects to the composition. The colorant may be added to the composition in any suitable form, e.g. in the form of discrete particles, dispersions, solutions and / or flakes. A single colorant or a mixture of two or more colorants may be used.

Exemplary colorants include pigments, dyes and tinting agents such as those used in the paint industry and / or those listed in the Dry Color Manufacturers Association (DCMA) as well as special effect compositions. The colorant includes, for example, fine powdery solids which are insoluble or wettable under the conditions of use. The colorant may be organic or inorganic and may not aggregate or aggregate. The colorant may be included by the use of a grinding vehicle, for example an acrylic grinding vehicle, and the use of such a vehicle will be familiar to those skilled in the art.

Exemplary pigment and / or pigment compositions include, but are not limited to, carbazole dioxazine pigments, azo, monoazo, disazo, naphthol AS, salt type (lake), benzimidazolone, condensates, metal complexes, Anthraquinone, indanthrone, anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, pyranthrone, anthanthrone, anthraquinone, , Dioxazine, triarylcarbonium, quinophthalone pigments, diketopyrrolopyrrole red ("DPPBO red"), titanium dioxide, carbon black and mixtures thereof. The terms "pigment" and "colored filler" may be used interchangeably.

Exemplary dyes include those that are non-limitingly solvent and / or aqueous based, such as phthalogreen or blue, iron oxide, bismuth vanadate, anthraquinone, perylene, aluminum and quinacridone.

Exemplary tinting agents include, but are not limited to, pigments dispersed in an aqueous or water-miscible carrier, such as AQUA-CHEM 896, commercially available from Degussa, Inc., And CHARISMA COLORANTS and MAXITONER INDUSTRIAL COLORANTS, which are commercially available from a precision dispersion of Eastman Chemical, Inc.

As indicated above, the colorant may be present in the form of a dispersion, including, but not limited to, a nanoparticle dispersion. The nanoparticle dispersion may comprise one or more highly dispersed nanoparticle coloring and / or colorant particles that produce the desired visible color and / or opacity and / or visual effects. The nanoparticle dispersion may contain colorants such as pigments or dyes having a particle size of less than 150 nm, e.g., less than 70 nm, or less than 30 nm. Nanoparticles can be produced by milling an organic or inorganic pigment stock with a milling medium having a particle size of less than 0.5 mm. Exemplary nanoparticle dispersions and methods for their preparation are identified in U.S. Patent No. 6,875,800 B2, which is incorporated herein by reference. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation, and chemical abrasion (i.e., partial dissolution). To minimize re-aggregation of the nanoparticles in the coating, a dispersion of resin-coated nanoparticles may be used. As used herein, "dispersion of resin-coated nanoparticles" refers to a continuous phase wherein dispersed "composite fine particles" containing nanoparticles and resin coatings on the nanoparticles are dispersed. Exemplary resin-coated nanoparticle dispersions and methods for their preparation are described in U.S. Patent Application Publication No. 2005-0287348 A1, filed June 24, 2004, U.S. Provisional Application No. 60 / 482,167, filed June 24, 2003, And U.S. Patent Application No. 11 / 337,062, filed January 20, 2006, which is also incorporated herein by reference.

Exemplary special effect compositions that may be used include, but are not limited to, one or more cosmetic effects such as, for example, reflectance, pearlescent, metallic luster, phosphorescence, fluorescence, photochromic phenomena, photosensitivity, heat discoloration phenomena, goniochromism and / And / or < / RTI > Additional special effect compositions may provide other perceptible properties, such as opacity or texture. In certain embodiments, the special effect composition can create a color shift such that the color of the coating changes when the coating is viewed at different angles. Exemplary color effect compositions are identified in U.S. Patent No. 6,894,086, which is incorporated herein by reference. The additional color effect composition may comprise transparent colored mica and / or synthetic mica, coated silica, coated alumina, transparent liquid crystal pigment, liquid crystal coating and / or any composition wherein the interference is from a difference in refractive index in the material But is not generated due to a difference in refractive index between the surface of the substance and air.

In certain embodiments, the photosensitive composition and / or photochromic composition (its color reversibly changes upon exposure to one or more light sources) may be used in the present invention. The photochromic and / or photosensitive composition may be activated by exposure to a particular wavelength of irradiation. When the composition is excited, the molecular structure changes and the modified structure exhibits a new color that is different from the original color of the composition. When the exposure to the radiation is removed, the photochromic and / or photosensitive composition can be restored to its resting state, where the original color of the composition is restored. In certain embodiments, the photochromic and / or photosensitive composition can be achromatic in its unexcited state and can exhibit color in an excited state. A full color-change can occur within a few seconds to a few minutes, for example between 20 and 60 seconds. Exemplary photochromic and / or photosensitive compositions include photochromic dyes.

In certain embodiments, the photosensitive composition and / or photochromic composition may be associated and / or at least partially bound to the polymeric and / or polymeric material of the polymerizable component by, for example, covalent bonds. A photosensitive composition associated with and / or at least partially bound to the polymer and / or polymeric component in accordance with certain embodiments of the present invention, as opposed to some coatings capable of moving the photosensitive composition out of the coating and crystallizing into the substrate, and / RTI > and / or photochromic composition migrates to a minimum outside the coating. Exemplary photosensitive and / or photochromic compositions and methods of making the same are identified in U.S. Patent Application No. 10 / 892,919, filed July 16, 2004, which is incorporated herein by reference.

In general, the colorant may be present in any amount sufficient to impart the desired visual and / or color effect to the coating composition. The colorant may comprise from 1 to 65% by weight, for example from 3 to 40% by weight or from 5 to 35% by weight, based on the total weight of the composition.

After deposition, the coating is often heated to cure the deposited composition. The heating or curing process is often carried out at a temperature ranging from 120 to 250 ° C, for example from 120 to 190 ° C, for a period ranging from 10 to 60 minutes. In certain embodiments, the thickness of the resulting film is 10 to 50 占 퐉.

As will be appreciated from the foregoing description, certain embodiments of the present invention also relate to a method of preventing rust contamination of a coating apparatus, even in the process of coating an iron-based substrate, even in the absence of a filtration apparatus. In certain embodiments, the method has a pH of from 4 to 5.5 and is (a) a group IIIB and / or IVB metal compound; (b) a phosphate ion; And (c) water, or, in some cases, essentially consists of these. In such embodiments of the method, the phosphate ions (i) is sufficient to prevent insoluble formation of rust in the bath in nature, (ii) IIIB having at least 10 mg / ft ² covering rate on the ferrous metal member Group or Group IVB metal film in an amount insufficient to prevent deposition of the metal film. In certain other embodiments, the process is conducted in a manner that iron is removed from a pretreatment bath that contains substantially no phosphate ions during operation in certain embodiments, and in other particular embodiments, comprises Group IIIB and / or Group IVB metals comprising phosphate ions Off-shift method. The off-shift method comprises: (a) reducing the pH of the pretreatment bath by at least 0.2; (b) adding phosphate ions to the pretreatment bath of (a); (c) adding an oxidizing agent to the pretreatment bath of (b); And (d) raising the pH of the pretreatment bath of (c) by at least 0.2. In the off-shift method of removing iron from the pretreatment bath, insoluble rust can essentially be removed from the pretreatment bath. In certain embodiments, the off-shift method includes filtering the pretreatment bath using a filtration device.

As can also be seen, the invention relates to a method of coating an iron metal substrate. In certain embodiments, the method comprises: (A) contacting the ferrous metal substrate with (a) a Group IIIB and / or Group IVB metal compound; (b) a phosphate ion; And (c) contacting, with the aqueous pretreatment composition comprising, or in some cases essentially consisting of, the water, wherein the phosphate ion is added to the bath of the pretreatment composition in an amount sufficient to essentially prevent the formation of insoluble rust in the bath Maintained; And then (B) contacting the substrate with a coating composition comprising a film-forming resin to form a coated metal substrate exhibiting corrosion resistance characteristics. In another specific embodiment, the method comprises the steps of: (a) removing iron from the pretreatment bath when the pretreatment bath is off-shifted; And then (b) contacting the ferrous metal substrate with an aqueous pretreatment composition having a pH of from 4 to 5.5 and (i) comprising, or in some cases essentially consisting of, a Group IIIB and / or Group IVB metal, Wherein the pretreatment composition is substantially free of phosphate ions in certain embodiments; And (c) contacting the substrate with a coating composition comprising a film-forming resin to form a coated metal substrate exhibiting corrosion resistance. In this way, removing iron from the pretreatment bath when the pretreatment bath is off-shifted comprises the steps of: (a) reducing the pH of the pretreatment bath by at least 0.2; (b) adding phosphate ions to the pretreatment bath of (a); (c) adding an oxidizing agent to the pretreatment bath of (b); And (d) raising the pH of the pretreatment bath of (c) by at least 0.2, or in some cases essentially consists of these. As used herein, the term " corrosion resistance "refers to a measure of corrosion protection on a metal substrate using the test described in ASTM B117 (salt spray test). In this test, the coated substrate is scribed with a knife according to ASTM D 1654-92 to expose the bare metal substrate. The scribed substrate is placed into a test chamber which is bathed on a substrate with an aqueous salt solution. The chamber is maintained at a constant temperature. The coated substrate is exposed to a salt spray environment for a specified time, e.g., 250, 500, or 1000 hours. After exposure, the coated substrate is removed from the test chamber and corrosion is evaluated according to the scribe traces. Corrosion is measured with a " scribe creep ", which is defined as the total distance in mm in which corrosion has progressed along the scribe measured above. If the substrate is referred to as "indicating corrosion resistance ", it means that if the substrate is coated with a polyester powder paint commercially available from PPG Industries, Inc. as PCT79111 according to the manufacturer's instructions, Means that the scribe creep on the ferrous metal substrate after testing according to ASTM B117 is not more than 3 mm.

The following examples illustrate the invention and should not be construed as limiting the invention to the details of these examples. All parts and percentages throughout the specification, as well as the examples, are by weight unless otherwise indicated.

Example

Example  One

In one experiment, five clean steel sheets were placed in an aqueous solution containing fluorozirconic acid and phosphoric acid (90 ppm Zr and 10 ppm PO ₄ ^-3 ) at a pH of about 1.8 to 2.4. After establishing a bivalent iron concentration of about 30 ppm, the plate was removed from the clear solution and divided into one gallon (3.78 liters) portions.

The first gallon was further subdivided into 700 ml portions, and phosphoric acid (75% by weight) was added thereto to obtain a series of baths having phosphate ions of 10, 25, 50, 75 and 100 ppm. The same series of phosphate levels were repeated with zirconium at 125, 150 and 200 ppm.

The pH of all sample baths was adjusted to 5.0. A bath containing 30 ppm of ferric iron and various amounts of zirconium and phosphate ions was left in the atmosphere for two days. Two days later, the appearance of each bath was observed. The results summarized in Table 1.0 below show that in this example a zirconium bath containing 30 ppm total iron is converted from brown to white in the presence of 25 to 50 ppm phosphate ions. Brown appearance indicates the formation of iron oxide or oxy iron hydroxide.

The result matrix showed that all 10 ppm PO ₄ ^{- 3} baths formed a green deposit and formed brown sediments almost equally, ie, regardless of the Zr level. The next brightest color was all 25 ppm PO ₄ ^-3 bath, which also formed a lighter colored precipitate. All of the 50 ppm PO ₄ ^-3 baths formed an almost inconspicuous off-white crystalline precipitate and were almost colorless. 75 and 100 ppm PO ₄ ^-3 bath formed a white crystalline precipitate and were all colorless. This white precipitate was iron phosphate, possibly with a slight amount of zirconium compounds.

In this embodiment, when a ferrous metal substrate is treated using a pretreatment bath with a phosphate to trivalent iron weight ratio of at least 1: 1, for example at least 1.2: 1, for example from 1 to 1.8: 1, IIIB and / or IVB Lt; RTI ID = 0.0 > metal-containing < / RTI > pre-treatment bath.

[Table 1.0]

Example  2

The steel sheet was cleaned using a conventional alkaline-based cleaner, washed twice with tap water, treated in a bath containing 10 to 150 ppm of zirconium and 10 to 100 ppm of phosphate, and then rinsed with tap water. The treated steel sheet was painted with P590 cationic epoxy electrodeposition coating or PCT79111 triglycidyl isocyanurate-polyester powder coating (both available from PPG Industries, Inc.). Corrosion performance was determined by exposing the zirconium treated and fired plates to neutral salt-spray in accordance with ASTM B117 for the times shown in Table 2.0. In this test, the appropriate performance for cationic epoxy electrodeposition coating over 1000 hours of neutral salt spray exposure was a half width scribe loss of 4.0 to 5.0 mm. The proper performance for TGIC-polyester powder paint at neutral salt spray-exposed 500 hours was 2.0 to 3.0 mm width scribe loss. The following results show that when the phosphate ion is added to the zirconium treatment bath, acceptable corrosion performance is obtained. At low concentrations of phosphate ions, as in Example 1.0, the treatment bath turns brown, indicating the presence of iron oxide or oxy iron hydroxide.

[Table 2.0]

Example  3

A pretreatment solution was prepared and added thereto while increasing the amount of hexafluorozirconic acid. Before coating the cold rolled steel sheet, the pH of the bath was adjusted to 4.7. Plates from ACT Laboratories (Hillsdale, Mich.) Were first spray-cleaned with an alkaline detergent (PPI Industries Chemclin 611L, 2% and 140-150 ° F), washed twice and placed in the pretreatment zone. A zirconium bath was sprayed on the plate at 9 psi for 60 seconds. Then, it was washed with tap water, finally washed with deionized water, and then introduced into an infrared drying step.

Plate samples were obtained at zirconium bath levels of 0, 10, 15, 20, 50 and 80 ppm. Each section was analyzed by XPS (X-ray photoelectron spectroscopy) to determine the layer thickness of zirconium in the coating. The depth of the zirconium layer was measured in nanometers when the profile crossed to the 10% atomic% level. The results for depth are plotted against the zirconium bath concentration, as shown in Fig.

Using the same series of plates, an anionic acrylic electrodeposition coating, available from PPG Industries, Inc. as Powercron 395, was applied to three plates at each level and then tested according to ASTM B117 and D1654-92 Corrosion test. The results are shown in Fig. The results confirm that it achieves a good degree of corrosion protection consistent with achieving the minimum thickness from a bath having 20 ppm zirconium.

Example  4

Indeed, baths heavily contaminated with rust are opaque brownish red and appear before the appearance of a translucent orange solution, which means that it has initially been converted to an insoluble trivalent iron complex. In one experiment, a 10 gallon low pH bath (about 2.7) containing 100 ppm zirconium was sprayed on the steel plates for several hours until the total iron reached 50 ppm. The ferric iron was about 40 ppm. The bath contained 10 ppm of soluble tribasic iron ions, but it was clear and colorless. A large sample was divided into several portions to determine the level to prevent the initial discoloration of the bath after raising the pH to 5 while increasing the level of phosphate. For the control sample without phosphate, the color of the bath began to change immediately after increasing the level of trivalent iron to 24 ppm. The results of this experiment are shown in Table 3.0.

[Table 3.0]

As P0 ₄ level increases, the color change is not intense enough to phosphate takes longer zero control. In addition, the pH dropped below the level indicated in the table after overnight storage, indicating the completion of the oxidation and precipitation steps. The pH decrease was smaller as more phosphate was used. After a certain level of phosphate, the pH remained constant, indicating an excess of the amount required for the trivalent iron. For several days, the sediment quality was clear as shown in Table 3.0. In the absence of sufficient phosphate in the system, the precipitate developed into a coherent brown oxide, leading to a significant reduction in pH. In the presence of sufficient phosphate, the precipitate was white and had a density that facilitated the removal of iron before being transferred downstream.

Zirconium levels were also determined to determine the effect of any excess phosphate. Figure 3 shows that some zirconium is depleted in the system, but the losses are not significant. As the phosphate converts the soluble trivalent iron complex into insoluble iron phosphate, the equivalent point of addition of the phosphate to the trivalent iron is known by the pH plateau. This occurred at about 35 to 40 ppm of phosphate relative to 24 ppm of trivalent iron.

Thus, in the above working bath, only 25 to 35 ppm of phosphate per 24 ppm of trivalent iron was sufficient to inhibit the development of the reddish brown bath, where the zirconium was only slightly depleted. The bath life for this embodiment can be much longer than typically seen in competitive industrial baths based on Group IIIB and / or IVB metals but not phosphate ions. The ratio of phosphate to trivalent iron is in the range of 1: 1 to 1.8: 1 by weight. Higher rates can start to exhaust too much zirconium.

Example  5

An iron-containing concentrate was obtained by hanging a clean steel sheet over a two-day period in a solution of hexafluorozirconic acid in deionized water containing no phosphate. The final ferric iron level was about 900 ppm and the ferric iron was 33 ppm. The concentrate was then diluted with tap water to provide approximately 20 ppm of bivalent iron and 3 ppm of trivalent iron. Phosphoric acid was added in varying amounts and then enough hydrogen peroxide was added to convert all the bivalent iron to trivalent iron. The pH was then adjusted to 4.7 for each bath. After standing for one day, the phosphate and zirconium were analyzed for bath. The results are shown in Fig. Obviously, most of the original zirconium 65 ppm in solution was retained, although it was sufficient to remove 20 ppm of trivalent iron with about 30 ppm of phosphate.

Example  6

Example 6 was conducted to demonstrate that trivalent iron (Fe ⁺³ ) can be removed from the pretreatment bath off-shift.

A stock solution was prepared from 3 liters of tap water and 1.2 g of fluorozirconic acid solution (45%). The stock solution is intended for 85 ppm Zr. To this was added 0.38 ml of iron sulfate (50% solution) to form a target solution having 20 ppm of trivalent iron ions. The stock solution had a pH of 2.9.

The stock solutions were divided into baths A to D, each containing 900 ml of stock solution. As will be described in more detail below, a Hach meter was used in this example (Examples 6 and 7) to measure the ^bivalent iron (Fe ⁺² ) and total iron concentrations at various time points. When it is desirable to determine the concentration of trivalent iron (Fe ⁺³ ) in a particular bath, the concentration of trivalent iron is calculated as the difference between the total iron concentration and the bivalent iron concentration. In Example 6, none of Baths A to D contained any divalent iron (Fe ⁺² ) at any measurement time point.

The bath A was used as a control and the ferric iron (Fe ⁺³ ) and the total iron concentration (ppm) of the bath B, C and D (treated as described below) were compared.

0.1 g of an alkaline solution commercially available from PPG Industries, Inc. was added as an alkaline feed to remove bath A to obtain a pH of 3.4. As shown in Figure 5, the concentration of trivalent iron (Fe ⁺³ ) in bath A was about 18.6 ppm during the 72 hour experimental period. There was a nearly invisible green-colored deposit formed in bath A. This data confirms that the ferric iron (Fe ⁺³ ) is very stable in the pH range of about 3.4.

0.5 g of Chemfil buffer was added to a stock solution of 900 ml of bath B to raise the pH of the bath to 4.8, which is within the standard operating range for the bath containing the pretreatment composition described herein. As shown in FIG. 5, the concentration of the trivalent iron (Fe ⁺³ ) in the bath B was reduced to about 2 ppm at an initial concentration of about 21 ppm at about 2 hours after the pH of the pretreatment bath was raised to 4.8. These data indicate that most of the soluble trivalent iron has been converted to rust or iron oxide which is insoluble in the pretreatment composition. The rusty precipitate could be seen in bath B at about 2 hours after the pH was raised.

0.09 g of a monosodium phosphate solution (45% by weight), supplied as a Zirconium bond P, marketed by Pfizer Industries, Inc. of Euclid, Ohio, was added to a 900 ml stock solution of Bath C. Bath C contained 14 ppm of phosphate and had a stable pH of 2.9 over an experimental period of 72 hours. 5, the ferric iron (Fe < ⁺³ >) concentration in bath C decreased from about 18 ppm to about 12 ppm for the first 2 hours of the experiment, followed by 7 ppm Lt; / RTI > A white precipitate was visible in bath C within the first hour of the experiment and at the end of the experiment, a slightly reddish brown precipitate formed, indicating that the removal of the trivalent iron is gradual and incomplete when the pH is below normal operating levels.

0.09 g of a monosodium phosphate solution (45% by weight) provided as zircon bond P was added to a 900 ml stock solution of bath D. Bath D contained 34 ppm of phosphate. As shown in Fig. 5, the concentration of trivalent iron (Fe ⁺³ ) in D of the bath was 20 ppm. 0.5 g of Chemfil buffer was added to bath D to raise the pH to 4.75 and the bath immediately clouded. After precipitating the crystals, the bath samples were filtered with a 5 micron syringe filter and the filtrate was examined for the total amount of iron. The concentration of trivalent iron in bath D was 2 ppm and 1.9 ppm after 2 hours (at the end of the experiment). The bath was transparent and had a small amount of white precipitate.

The data from Example 6 shows that the addition of phosphate to the pretreatment bath substantially removed all of the trivalent iron in a short period of time after removing most of the trivalent iron at low pH and raising the pH back to operating range. This data confirms that the trivalent iron can be removed from the pretreatment bath when the bath is off-shifted.

Example  7

The data shown in Figure 5 and described in Example 6 showed that the trivalent iron was removed from the pretreatment bath by adding phosphate to the pretreatment bath at low pH. However, in practice, the pretreatment bath used to treat the substrate often contains bivalent iron which must be converted to trivalent iron to remove from the pretreatment bath. The data shown in Example 7 and Table 4 and described herein demonstrate that the addition of oxidizing agent to the pretreatment bath improved the removal of iron which was initially brittle.

A stock solution was prepared from 3 liters of tap water and 1.2 g of fluorozirconic acid solution (45%). The stock solution is intended for 85 ppm Zr. To this was added 0.32 g of iron sulfate heptahydrate to form a target solution having 20 ppm of iron ions (Fe ^{+ 2} ) and 23 ppm of total iron. The stock solution had a pH of 3.1.

The stock solutions were divided into baths E to G, each containing 900 ml of stock solution. Bath E was used as a control and compared with the bivalent iron (Fe ⁺² ) and total iron concentration (ppm) of Bath F and G (treated as described below). Using a hach meter, the bivalent iron and total iron concentrations were monitored in each bath at periodic intervals over an experimental period of 44 hours.

Bath E was used as a control. Bath E had an initial pH of 3.1. A few drops of Kemphenyl buffer were added to the bath to raise the pH to 3.5 and this remained steady for the duration of the experiment, as shown in Table 4. In addition, as shown in Table 4, the total iron concentration (ppm) in bath E dropped from 22.8 ppm to 22.1 ppm at the end of the 44-hour experiment. The concentration of ² Fe (Fe ⁺² ) was 19.8 ppm for the first time and dropped to 15.7 ppm after 44 hours of experiment. The bath was transparent during the experiment and no red color was formed. These data indicate that all iron in the bath remains bivalent in solution and only a small amount of bivalent iron has been converted to trivalent iron. These data show that there is only minimal conversion from bivalent to trivalent iron at low pH (ie, below the working pH).

0.093 g monosodium phosphate (45% solution) was added to bath F to obtain a solution having 43 ppm phosphate and a ratio of PO ₄ : total iron of about 1.8: 1. Then, 0.5 g of Chemfil buffer was added to the bath to obtain a pH of 4.7. The pH of bath F decreased slightly over the duration of the experiment and was 4.38 at 44 hours. As shown in Table 4, the total iron concentration in Bath E dropped from 18.8 ppm at the initial 22.8 ppm to 18.5 ppm at 30 minutes and dropped to 14.7 ppm at the end of the 44-hour experiment. The concentration of divalent iron initially was 19.8 ppm, decreased to about 17.2 ppm for 30 minutes, and 12.4 ppm at the end of the 44 hour experiment. Some white precipitate indicating the formation of iron phosphate was formed in the bath during the experiment. This data shows that after the addition of the phosphate, the pH was increased from 4.38 to 4.7, indicating that only a portion of the soluble iron was removed as iron phosphate, which is not to be bound by theory, Relatively slow and limited by pH-related equilibrium.

As shown in Table 4, Bath G initially had a pH of 3.0, a total iron concentration of 22.8 ppm and a bivalent iron concentration of 19.8 ppm. Immediately after adding 0.1 g of monosodium phosphate (45% solution) to bath G, 0.32 g of hydrogen peroxide (3% by weight solution) was added. About 15 minutes after the addition of hydrogen peroxide, the total iron concentration decreased to 10.2 ppm, the bivalent iron concentration decreased to 0.4 ppm, and the pH was 2.6. Some white precipitate formed in the bath, indicating that the iron-phosphate complex was partially complete. Next, the pH of the bath was increased to 4.7 by addition of 0.6 g of Chemfil buffer and after approximately 15 minutes (ie, after 46 minutes from the start of the experiment) almost all of the iron was removed, the total iron concentration was 5 ppm, ppm. At the end of the experiment (ie, 44 hours after initiation), the pH of the bath was 4.6, the total iron concentration was 0.24 ppm and the concentration of bivalent iron was 0.02 ppm. These data showed that the addition of phosphate and hydrogen peroxide to the bath significantly improved iron removal from the bath at the working pH.

[Table 4.0]

Example  8

In this Example, 3.60 g of hexafluorozirconic acid was added to 3 liters of water to obtain a solution having 240 ppm of zirconium, thereby preparing an operation pre-treatment bath. The amount of chemfil buffer sufficient to raise the pH of the solution to 4.5 was added. 0.31 g of iron sulfate heptahydrate was added to obtain 20 ppm of bivalent iron. To prevent the formation of rust particles, approximately 14 drops of hexafluorozirconic acid were immediately added to reduce the pH to 3.3. The bath was transparent. Using a hach meter, the total iron concentration was measured at 23.2 ppm and the ferric iron was 19.5 ppm.

Phosphate was added to the bath at a molar ratio of about 1: 1 (or a 1.8: 1 mole ratio) to the total iron precipitated. For this bath, 41.5 ppm of phosphate from 0.175 g of phosphoric acid solution (75% by weight) was added in about 8 to 9 ppm excess. After mixing for 1 minute, 1.27 g of hydrogen peroxide solution (3% by weight) was then added in a molar ratio of 1: 1 relative to the bivalent iron (slightly over). Divalent iron was converted to trivalent iron in one minute.

To precipitate all the trivalent iron with phosphoric acid iron, the pH of the bath was gradually increased to 4.75 by dropwise addition of the chemfil buffer. If it rises too fast, some insoluble iron oxide may be formed instead of iron phosphate as rust. As the pH increases, white turbidity develops in the bath, which eventually flocculates and completely sinks within 10 minutes, yielding a clear bath. This final solution contains 0.2 ppm total iron, and no bivalent iron is detected at all. The residual phosphate was 8.5 ppm, which is consistent with the mass balance calculation.

It will be understood by those skilled in the art that changes may be made in the embodiments described above without departing from the broad inventive concept. Accordingly, it is to be understood that the invention is not to be limited to the specific embodiments disclosed, but is intended to cover modifications within the spirit and scope of the invention as defined by the appended claims.

Claims (23)

A method of removing iron from a pretreatment bath containing a pretreatment composition comprising a Group IIIB and / or Group IVB metal,
(a) reducing the pH of the pretreatment bath by at least 0.2;
(b) adding phosphate ions to the pretreatment bath of (a);
(c) raising the pH of the pretreatment bath of (b) by 0.2 or more; And
(d) removing insoluble sludge formed in the pretreatment bath of (c)
Lt; / RTI >
Is carried out in the absence of the article to be coated by the pretreatment composition,
Wherein the pretreatment bath is substantially free of phosphate ions during operation. The method according to claim 1,
Wherein the pH of the pretreatment bath is reduced by 1.0 or more. The method according to claim 1,
Wherein the reducing comprises adding an acid to the pretreatment bath. The method of claim 3,
Wherein said acid comprises a Group IVB fluorometallic acid, phosphoric acid, sulfuric acid, sulfamic acid, nitric acid or mixtures thereof. The method of claim 3,
Wherein the acid comprises hexafluorozirconic acid. The method according to claim 1,
Wherein the source of phosphate ions comprises an alkali metal orthophosphate, ammonium orthophosphate or a mixture thereof. The method according to claim 1,
Wherein the source of the phosphate ion comprises monosodium phosphate. The method according to claim 1,
Wherein the pretreatment bath of (c) is substantially free of iron. The method according to claim 1,
Further comprising the step of adding an oxidizing agent to the pretreatment bath of (b) above. 10. The method of claim 9,
Wherein the oxidant comprises a peroxide compound. The method according to claim 1,
Further comprising the step of filtering the pretreatment bath of (c) above. delete The method according to claim 1,
Wherein said Group IIIB and / or Group IVB metal comprises zirconium. delete A method of removing iron from a pretreatment bath containing a pretreatment composition comprising a Group IIIB and / or Group IVB metal,
(a) adding an acid to the pretreatment bath to reduce the pH of the pretreatment bath to less than 4.0;
(b) adding phosphate ions to the pretreatment bath of (a);
(c) raising the pH of the pretreatment bath of (b) to 4 to 5.5; And
(d) removing insoluble sludge formed in the pretreatment bath of (c)
Lt; / RTI >
Is carried out in the absence of the article to be coated by the pretreatment composition,
Wherein the pretreatment bath is substantially free of phosphate ions during operation. 16. The method of claim 15,
Wherein the acid comprises hexafluorozirconic acid. 16. The method of claim 15,
Wherein the source of phosphate comprises monosodium phosphate. 16. The method of claim 15,
Further comprising the step of adding an oxidizing agent to the pretreatment bath of (b) above. 19. The method of claim 18,
Wherein the oxidant comprises a peroxide compound. 16. The method of claim 15,
Further comprising the step of filtering the pretreatment bath of (c) above. 16. The method of claim 15,
Wherein the pretreatment composition in the pretreatment bath after step (c) comprises a weight ratio of 1: 1 to 1.7: 1 part by weight of phosphate to trivalent ferric ions. delete delete

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