HK1196644A - Zirconium pretreatment compositions containing a rare earth metal associated methods for treating metal substrates, and related coated metal substrates - Google Patents

Description

Rare earth metal-containing zirconium pretreatment compositions, related methods of treating metal substrates, and related coated metal substrates

Statement regarding federally sponsored research

The invention was made with government support under contract number No. w912hq-09-C-0038 approved by SERDP (strategic environmental research and development project). The U.S. government has certain rights in this invention.

Technical Field

The present invention relates to pretreatment compositions, methods of treating metal substrates, including aluminum-containing substrates and iron-containing substrates such as cold rolled steel and zinc electroplated steel. The invention also relates to a coated metal substrate.

Background information

It is conventional to use protective coatings on metal substrates to improve corrosion resistance and paint adhesion. Conventional techniques for coating such substrates include techniques that include pretreating the metal substrate with a phosphate conversion coating and a chromium-containing wash. However, the use of such phosphate and/or chromium containing compositions creates environmental and health concerns.

As a result, chromate-free and/or phosphate-free pretreatment compositions have been developed. Such compositions are typically based on chemical mixtures that react in some way with the substrate surface and bond to it to form a protective layer. For example, pretreatment compositions based on group IIIB or group IVB metal compounds have recently become more popular. Such compositions often contain a source of free fluorine, i.e., fluorine that is isolated in the pretreatment composition rather than bonded to another element such as a group IIIB or IVB metal. The free fluorine etches the surface of the metal substrate, thereby promoting the deposition of a group IIIB or IVB metal coating. However, the corrosion resistance of these pretreatment compositions is generally significantly inferior to conventional phosphate and/or chromium containing pretreatments.

As a result, it would be desirable to provide a method of treating a metal substrate that overcomes at least some of the aforementioned deficiencies of the prior art, including the environmental deficiencies associated with the use of chromates and/or phosphates. Furthermore, it would be desirable to provide a method of treating a metal substrate that in at least some instances imparts corrosion resistance that is equal to or even better than the corrosion resistance imparted by the use of phosphate conversion coatings. It is also desirable to provide related coated metal substrates.

Disclosure of Invention

In certain aspects, the present invention relates to pretreatment compositions for treating metal substrates. These pretreatment compositions comprise (a) a rare earth metal and (b) a zirconyl compound.

In still other aspects, the present invention relates to a method of treating a metal substrate comprising contacting the substrate with the pretreatment composition described above.

Detailed Description

In the following detailed description, it is to be understood that the invention may assume various alternative variations and step sequences, except where expressly specified to the contrary. Moreover, other than in any operating examples, or where otherwise indicated, all numbers expressing, for example, quantities of ingredients used in the specification and claims are to be understood as being modified in all instances by the term "about". 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 desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

Also, it should be understood that any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of "1 to 10" is intended to include all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10.

In this application, the use of the singular includes the plural and plural encompasses singular, unless expressly stated otherwise. In addition, in this application, the use of "or" means "and/or" unless stated otherwise, even though "and/or" may be explicitly used in some cases.

As previously mentioned, certain embodiments of the present invention are directed to methods of treating metal substrates. Suitable metal substrates for use in the present invention include those that are often used in automobile bodies, components of automobile parts, and other articles, such as small metal parts, including fasteners, i.e., nuts, bolts, screws, pins, nails, clips, buttons, and the like. Specific examples of suitable metal substrates include, but are not limited to, cold rolled steel, hot rolled steel, zinc metal, zinc compound or zinc alloy coated steel, such as galvanized steel, hot dip galvanized steel, alloyed hot dip galvanized steel, and steel electroplated with a zinc alloy. Also, aluminum alloy, aluminum plated steel, and aluminum alloy plated steel substrates may be used. Other suitable non-ferrous metals include copper and magnesium and alloys of these materials. Further, in certain embodiments, the substrate may be a bare metal substrate, such as a cut edge of a substrate, and the remaining surface of the substrate is treated and/or coated. The metal substrate treated according to the method of the invention may be in the form of, for example, a metal sheet or fabricated part.

The substrate intended to be treated according to the method of the present invention may be first cleaned to remove grease, dirt, or other foreign matter. This is often done by using a medium or strong alkaline cleaner, such as those commercially available and commonly used in metal pretreatment processes. Examples of alkaline cleaners suitable for use in the present invention include Chemkleen163, Chemkleen177, Chemkleen2010LP and Chemkleen490MX, each of which is commercially available from PPG Industries, Inc. Such cleaners are often rinsed with water afterwards and/or before.

As previously mentioned, certain embodiments of the present invention are directed to pretreatment compositions and related methods of treating a metal substrate comprising contacting the metal substrate with a pretreatment composition comprising (a) a rare earth metal; and (b) a zirconyl compound. In certain embodiments, the pretreatment compositions are applied to the metal substrate without prior application of an electropositive metal (i.e., in a one-step pretreatment process). As used herein, the term "pretreatment composition" refers to a composition that reacts with and chemically alters a substrate surface by contacting the substrate surface and bonding thereto to form a protective layer.

Often, the pretreatment composition comprises a support (often an aqueous medium) such that the composition is in the form of a solution or dispersion of the rare earth metal compound and/or other pretreatment composition components in the support. In these embodiments, the solution or dispersion may be contacted with the substrate by any of a variety of known techniques, such as dipping or immersion, spraying, intermittent spraying, dipping followed by spraying, spraying followed by dipping, brushing, or rolling. In certain embodiments, the solution or dispersion is at a temperature of 60 to 150 ° f (15 to 65 ℃) when applied to a metal substrate. Contact times are often in the range of 10 seconds to 5 minutes, for example 30 seconds to 2 minutes.

As defined by IUPAC and used herein, the term "rare earth metal" refers to seventeen chemical elements of the periodic Table, including fifteen lanthanides (fifteen elements from atoms 57-71, from lanthanum to lutetium) plus scandium and yttrium. Where applicable, the metal itself may be used. In certain embodiments, a rare earth metal compound is used as the source of the rare earth metal. As used herein, the term "rare earth metal compound" refers to a compound that includes at least one element of the rare earth elements as defined above.

In certain embodiments, the rare earth metal compound used in the pretreatment composition is a compound of yttrium, cerium, praseodymium, or mixtures thereof. Exemplary compounds that can be used include praseodymium chloride, praseodymium nitrate, praseodymium sulfate, cerium chloride, cerium nitrate, cerium sulfate, cerium nitrate, yttrium chloride, yttrium nitrate, yttrium sulfate.

In certain embodiments, the rare earth metal compound is present in the pretreatment composition in an amount of at least 10ppm metal, such as at least 100ppm metal, or in some cases at least 150ppm metal (measured as elemental metal). In certain embodiments, the rare earth metal compound is present in the pretreatment composition in an amount of no greater than 5000ppm metal, such as no greater than 300ppm metal, or in some cases no greater than 250ppm metal (measured as elemental metal). The amount of rare earth metal in the pretreatment composition can be any combination of the recited values encompassed by the recited values.

As noted above, the pretreatment composition also includes a zirconyl compound. As defined herein, a zirconyl compound or a zirconium oxide compound refers to a chemical compound having a zirconyl (ZrO) group.

In certain embodiments, the zirconyl compound in the pretreatment composition comprises zirconyl nitrate (ZrO (NO)₃)₂) Zirconium oxyacetate (ZrO (C)₂H₃O₂)₂Zirconium oxycarbonate (ZrOCO)₃) Protonated zirconium basic carbonate (Zr)₂(OH)₂CO₃) Zirconium oxysulfate (ZrOSO)₄)₂Zirconium oxychloride (ZrO (Cl)₂Zirconium oxyiodide (ZrO (I)₂Zirconium oxybromide (ZrO (Br))₂Or mixtures thereof.

In certain embodiments, the ratio of zirconium (from the zirconyl compound) to rare earth metal (from the rare earth metal or rare earth metal compound) in the composition is 200/1 to 1/1, such as 100/1 to 2/1, or in certain embodiments, 30/1 to 10/1, such as 20/1.

In certain embodiments, the amount of zirconium of the zirconyl compound is present in the pretreatment composition in an amount of at least 10ppm zirconium, such as at least 100ppm zirconium, or in some cases at least 150ppm zirconium (measured on an elemental zirconium basis). In certain embodiments, the amount of zirconium from the zirconyl compound is present in the pretreatment composition in an amount of no greater than 5000ppm zirconium, such as no greater than 300ppm zirconium, or in some cases no greater than 250ppm zirconium (measured on an elemental zirconium basis). The amount of zirconium from the zirconyl compound in the pretreatment composition can be any combination of the recited values included in the recited values.

In certain embodiments, the pretreatment composition further comprises a group IVB and/or group VB metal. As used herein, the term "group IVB and/or group VB metal" refers to an element of group IVB or group VB of the CAS periodic table of elements, as shown, for example, in the Handbook of Chemistry and Physics, 68 th edition (1987), or a mixture of two or more such elements. Where applicable, the metal itself may be used. In certain embodiments, a group IVB and/or group VB metal compound is used. As used herein, when it is stated that the composition includes "a compound of a group IVB and/or group VB metal," it is meant that the composition includes at least one element of group IVB or group VB of the CAS periodic table of elements or a mixture of two or more such metals.

In certain embodiments, the group IVB and/or group VB metal compound used in the pretreatment composition is a compound of zirconium, titanium, hafnium, or mixtures thereof. Suitable zirconium compounds include, but are not limited to, hexafluorozirconic acid, alkali metal and ammonium salts thereof, ammonium zirconium carbonate, zirconyl nitrate, zirconium carboxylates, and zirconium hydroxy carboxylates, such as hydrofluorozirconic 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 hafnium compounds include, but are not limited to, hafnium nitrate.

In certain embodiments, the amount of metal from the group IVB and/or group VB metal compound included in the pretreatment composition, in combination with the amount of metal from the zirconyl compound, is at least 10ppm metal, such as at least 100ppm metal, or in some cases at least 150ppm metal (measured on an elemental metal basis). In certain embodiments, the amount of metal from the group IVB and/or group VB metal compound included in the pretreatment composition, in combination with the amount of metal from the zirconyl compound, is no greater than 5000ppm metal, such as no greater than 300ppm metal, or in some cases no greater than 250ppm metal (measured on an elemental metal basis). The amount of metal from the group IVB and/or group VB metals and the zirconyl compound combined in the pretreatment composition can be any combination of the recited values encompassed by the recited values.

In certain embodiments, the pretreatment composition further comprises an electropositive metal. As used herein, the term "electropositive metal" refers to a metal that has a greater electropositive character than the metal substrate intended to be treated with the pretreatment composition. This means that in the present invention, the term "electropositive metal" includes metals that are less prone to oxidation than the metal of the metal substrate. As will be understood by those skilled in the art, the propensity of a metal to oxidize is referred to as the oxidation potential, which is expressed in volts and measured relative to a standard hydrogen electrode, which is arbitrarily assigned a zero oxidation potential. The table below gives the oxidation potentials of several elements. If in the table below the voltage value E of one element is greater than the element to which it is compared, this element is less prone to oxidation than the other element.

Element(s)	Half cell reaction	Voltage E
			Potassium salt	K++e→K	-2.93
Calcium carbonate	Ca2++2e→Ca	-2.87
			Sodium salt	Na++e→Na	-2.71
Magnesium alloy	Mg2++2e→Mg	-2.37
			Aluminium	Al3++3e→Al	-1.66
Zinc	Zn2++2e→Zn	-0.76
			Iron	Fe2++2e→Fe	-0.44
Nickel (II)	Ni2++2e→Ni	-0.25
			Tin (Sn)	Sn2++2e→Sn	-0.14
Lead (II)	Pb2++2e→Pb	-0.13
			Hydrogen	2H++2e→H2	-0.00
Copper (Cu)	Cu2++2e→Cu	0.34
			Mercury	Hg2 2++2e→2Hg	0.79
Silver (Ag)	Ag++e→Ag	0.80
			Gold (Au)	Au3++3e→Au	1.50

Thus, as will be apparent, when the metal substrate comprises one of the materials listed previously, such as cold rolled steel, hot rolled steel, steel coated with zinc metal, zinc compounds or zinc alloys, hot dip galvanized steel, alloyed hot dip galvanized steel and steel electroplated with zinc alloys, aluminum plated steel, aluminum alloy plated steel, magnesium and magnesium alloys, suitable electropositive metals for deposition thereon in accordance with the present invention include, for example, nickel, copper, silver and gold and mixtures thereof.

In certain embodiments, the source of the electropositive metal in the pretreatment composition is a water soluble metal salt. In certain embodiments of the invention, the water-soluble metal salt is a water-soluble copper compound. Specific examples of water-soluble copper compounds (which are 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, disodium copper ethylenediaminetetraacetate tetrahydrate, copper bromide, copper oxide, copper hydroxide, copper chloride, copper fluoride, copper gluconate, copper citrate, copper lauroylsarconate, copper formate, copper acetate, copper propionate, copper butyrate, copper lactate, copper oxalate, copper phytate, copper tartrate, copper malate, copper succinate, copper malonate, copper maleate, copper benzoate, copper salicylate, copper aspartate, copper glutamate, copper fumarate, copper glycerophosphate, sodium copper chlorophyllin, copper fluorosilicate, copper fluoroborate and copper iodate, as well as copper salts of carboxylic acids in the homologous series formic acid to capric acid, copper salts of polybasic acids in the homologous series oxalic acid to suberic acid and copper salts of hydroxycarboxylic acids, including glycolic acid, lactic acid, tartaric acid, malic acid and citric acid.

When the copper ions provided by such a water-soluble copper compound precipitate as an impurity form of copper sulfate, copper oxide, or the like, it is preferable that a complexing agent be added, which inhibits the precipitation of copper ions, and thus stabilizes them in solution as a copper complex.

In certain embodiments, the copper compound is as a copper complex salt such as K₃Cu(CN)₄Or Cu-EDTA, which may be present stably in the composition it has, but which may also form copper complexes which may be present stably in the composition by combining complexing agents with compounds which are themselves poorly soluble. Examples thereof include copper cyanide complex (formed of a combination of CuCN and KCN or a composition of CuSCN and KSCN or KCN) and Cu-EDTA complex (formed of CuSO)₄And edta.2na).

As the complexing agent, a compound capable of forming a complex with copper ions; examples thereof include inorganic compounds such as cyanide compounds and thiocyanate compounds, and polycarboxylic acids, and specific examples thereof include ethylenediamine tetraacetic acid, salts of ethylenediamine tetraacetic acid such as disodium dihydrogen ethylenediamine tetraacetic acid dihydrate, aminocarboxylic acids such as nitrilotriacetic acid and iminodiacetic acid, oxycarboxylic acids such as citric acid and tartaric acid, succinic acid, oxalic acid, ethylenediamine tetramethylene phosphonic acid, and glycine.

In certain embodiments, the content of electropositive metal, e.g., copper, in the pretreatment composition is at least 1ppm, e.g., at least 5ppm, or in some cases at least 10ppm total metal (measured on an elemental metal basis). In certain embodiments, the electropositive metal is present in such pretreatment compositions in an amount of no greater than 500ppm, such as no greater than 100ppm, or in some cases no greater than 50ppm total metal (measured on an elemental metal basis). The amount of electropositive metal in the pretreatment composition can be in any combination of the recited values encompassed by the recited values.

The pretreatment composition may optionally comprise other materials, such as nonionic surfactants and adjuvants conventionally used in the pretreatment art. In aqueous media, water dispersible organic solvents such as alcohols having up to about 8 carbon atoms, e.g., methanol, isopropanol, and the like, may be present; or glycol ethers such as monoalkyl ethers of ethylene glycol, diethylene glycol or propylene glycol, and the like. When present, the water-dispersible organic solvent is typically used in an amount up to about 10 volume percent, based on the total volume of the aqueous medium.

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

In certain embodiments, the pretreatment composition further comprises a reaction accelerator such as nitrite ions, nitro-containing compounds, hydroxylamine sulfate, persulfate ions, sulfite ions, thiosulfate ions, peroxides, iron (III) ions, ferric citrate compounds, bromate ions, perchloride ions, chlorate ions, chlorite ions, as well as ascorbic acid, citric acid, tartaric acid, malonic acid, succinic acid, and salts thereof. Specific examples of suitable materials and their amounts are described in U.S. patent application publication No.2004/0163736A1 [0032] - [0041], the contents of which are incorporated herein by reference.

In certain embodiments, the pretreatment composition further comprises a filler, such as a silicic acid filler. Non-limiting examples of suitable fillers include silica, mica, montmorillonite, kaolinite, asbestos, talc, diatomaceous earth, vermiculite, natural and synthetic zeolites, cement, calcium silicate, aluminum silicate, sodium aluminum silicate, aluminum polysilicate, alumina silica gel, and glass particles. In addition to the silicic acid filler, other finely divided particulate, substantially water-insoluble fillers may also be used. Examples of such optional fillers include carbon black, charcoal, graphite, titanium oxide, iron oxide, copper oxide, zinc oxide, antimony oxide, zirconium oxide, magnesium oxide, aluminum oxide, molybdenum disulfide, zinc sulfide, barium sulfate, strontium sulfate, calcium carbonate, and magnesium carbonate.

As indicated, in certain embodiments, the pretreatment composition is substantially or, in some cases, completely free of chromates and/or heavy metal phosphates. As used herein, the term "substantially free" when used to refer to the absence of chromates and/or heavy metal phosphates, such as zinc phosphate, in the pretreatment composition means that these materials are not present in the composition to such an extent that they cause an environmental burden. That is, they substantially do not use and eliminate the formation of sludge such as zinc phosphate (formed when using a zinc phosphate-based treating agent). In the present invention, pretreatment compositions having less than 1 wt.% chromate and/or heavy metal phosphate (with the weight percent based on the total weight of the pretreatment composition) are considered to be "substantially free" of chromate and/or heavy metal phosphate.

In certain embodiments, the film coverage of the residue of the pretreatment coating composition is generally from 1 to 1000 milligrams per square meter (mg/m)²) E.g. 10-400mg/m². The thickness of the pretreatment coating can vary, but it is typically very thin, often less than 1 micron in thickness, in some cases it is 1-500nm, and in still other cases it is 10-300 nm.

After contact with the pretreatment solution, the substrate may be rinsed with water and dried, if desired.

In certain embodiments of the method of the present invention, after the substrate is contacted with the pretreatment composition, it is then contacted with a coating composition comprising a film-forming resin. Suitable techniques can then be used to contact the substrate with such coating compositions, including, for example, brushing, dipping, flow coating, spraying, and the like. In certain embodiments, however, such contacting comprises an electroplating step, as described in more detail below, wherein the electrodepositable composition is deposited onto the metal substrate by electrodeposition.

As used herein, the term "film-forming resin" refers to a resin that is capable of forming a self-sustaining continuous film on at least the horizontal surface of a substrate by removing any diluents or carriers present in the composition, or by curing at ambient or elevated temperatures. Conventional film-forming resins that can be used include, but are not limited to, those typically used in automotive OEM coating compositions, automotive finish coating compositions, industrial coating compositions, architectural coating compositions, coil coating compositions, aerospace coating compositions, and the like.

In certain embodiments, the coating composition comprises a thermosetting film-forming resin. As used herein, the term "thermoset" refers to a resin that is irreversibly "set" by curing or crosslinking, wherein the polymer chains of the polymer components are held together by covalent bonds. This property is often associated with a crosslinking reaction of the composition components, which is often induced, for example, by heat or radiation. 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 will not dissolve in the solvent. In other embodiments, the coating composition comprises a thermoplastic film-forming resin. As used herein, the term "thermoplastic" refers to a resin comprising a polymeric component that is not covalently bonded and thus undergoes liquid flow and is soluble in a solvent upon heating.

As previously mentioned, 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 metal substrate to be treated serves as an electrode, and a conductive counter electrode is placed in contact with the ionic electrodepositable composition. By passing an electric current between the electrode and the counter electrode while they are in contact with the electrodepositable composition, an adherent film of the electrodepositable composition will be deposited onto the metal substrate in a substantially continuous manner.

Electrodeposition is typically carried out at a constant voltage of 1 volt to several thousand volts, typically 50-500 volts. The current density is typically 1.0 to 15 amps per square foot (10.8-161.5 amps per square meter) and tends to decrease rapidly during the electrodeposition process, indicating the formation of a continuous self-insulating film.

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

In certain embodiments, the electrodepositable compositions used in certain embodiments of the present invention comprise as the primary film-forming polymer an active hydrogen-containing ionic (often cationic) electrodepositable resin. A wide variety of electrodepositable film-forming resins are known and can be used in the present invention, so long as the polymer is "water-dispersible," i.e., suitable for solubilization, dispersion, or emulsification in water. The water dispersible polymer is ionic in nature, i.e., the polymer will contain anionic functional groups to impart a negative charge, or often preferably as cationic functional groups to impart a positive charge.

Examples of film-forming resins suitable for use in the anionic electrodepositable composition are base-solubilized carboxylic acid-containing polymers, such as the reaction products or adducts of drying oils or semi-drying fatty acid esters with dicarboxylic acids or anhydrides; and the reaction product of a fatty acid ester, an unsaturated acid or anhydride, and any additional unsaturated modifying material that is further reacted with a polyol. Also suitable are at least partially neutralized interpolymers of hydroxyalkyl esters of unsaturated carboxylic acids, unsaturated carboxylic acids and at least one other ethylenically unsaturated monomer. Still another suitable electrodepositable film-forming resin comprises an alkyd-aminoplast vehicle, i.e., a vehicle comprising an alkyd resin and an amine-aldehyde resin. Still another anionic electrodepositable resin composition comprises a mixed ester of a resin polyol, as described, for example, in U.S. patent No.3749657, column 9, lines 1-75 and column 10, lines 1-13, the cited portions of which are incorporated herein by reference. Other acid functional polymers may also be used, such as phosphated polyepoxides or phosphated acrylic polymers, as known to those skilled in the art.

As noted above, it is often desirable that the active hydrogen-containing ionic electrodepositable resin (a) be cationic and capable of deposition on the 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 nos. 3663389; 3984299, respectively; 3947338, respectively; and 3947339. Often, these amine salt group-containing resins are used in combination with a blocked isocyanate curing agent. The isocyanate may be fully blocked as described in U.S. patent No.3984299, or the isocyanate may be partially blocked and reacted with the resin backbone, for example as described in U.S. patent No. 3947338. Also, one-component compositions as described in U.S. Pat. No.4134866 and DE-OS No.2707405 may be used as film-forming resins. In addition to the epoxy-amine reaction product, the film-forming resin may be selected from cationic acrylic resins, such as those described in U.S. patent nos. 3455806 and 3928157.

In addition to amine salt group-containing resins, quaternary ammonium salt group-containing resins may also be used, such as those formed by reacting an organic polyepoxide with a tertiary amine salt, as described in U.S. patent nos. 3962165; 3975346, respectively; and 4001101. Examples of other cationic resins are ternary sulfonium salt group-containing resins and quaternary phosphonium salt group-containing resins, such as those described in U.S. Pat. Nos. 3793278 and 3984922, respectively. Also, film-forming resins that cure via transesterification may be used, for example as described in european application No. 12463. In addition, cationic compositions prepared from mannich bases may be used, for example as described in U.S. patent No. 4134932.

In certain embodiments, the resin present in the electrodepositable composition is a positively charged resin comprising primary and/or secondary amine groups, such as described in U.S. patent nos. 3663389; 3947339, respectively; and 4116900. In U.S. Pat. No.3947339, a polyketimine derivative of a polyamine, such as diethylenetriamine or triethylenetetramine, is reacted with a polyepoxide. When the reaction product is neutralized with an acid and dispersed in water, free primary amine groups are generated. Likewise, equivalent products are formed when the polyepoxide is reacted with an excess of polyamines such as diethylenetriamine and triethylenetetramine, and the excess polyamine is vacuum stripped from the reaction mixture as described in U.S. Pat. Nos. 3663389 and 4116900.

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

As noted, the resin phase of the electrodepositable composition often further comprises a curing agent, which is adapted 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, although blocked isocyanates are often preferred for cathodic electrodeposition.

Aminoplast resins, which are often the preferred curing agents for anionic electrodeposition, are condensation products of amines or amides with aldehydes. Examples of suitable amines or amides are melamine, benzoguanamine, urea and similar compounds. Typically, the aldehyde used is formaldehyde, although the product can be made from other aldehydes, such as acetaldehyde and furfural. The condensation product contains a carbinol group or a similar alkanol group depending on the particular aldehyde used. Typically, these carbinol groups are etherified by reaction with an alcohol, for example a monohydric alcohol containing from 1 to 4 carbon atoms such as methanol, ethanol, isopropanol and n-butanol. Aminoplast resins are commercially available under the trademark CYMEL from American cyanamidCo. and RESIMENE from Monsanto Chemical Co.

The aminoplast curing agent is often used in conjunction with the active hydrogen-containing anionic electrodepositable resin in an amount of from 5% to 60% by weight, such as from 20% to 40% by weight, based on the total weight of resin solids in the electrodepositable composition.

As shown, blocked organic polyisocyanates are often used as curing agents in cathodic electrodeposition compositions. The polyisocyanate may be fully blocked as described in U.S. Pat. No.3984299 column 1, lines 1-68, column 2 and column 3, lines 1-15, or partially blocked and reacted with the polymer backbone as described in U.S. Pat. No.3947338 column 2, lines 65-68, column 3 and column 4, lines 1-30, the cited portions of which are incorporated herein by reference. By "blocked" is meant that the isocyanate group has reacted with a compound such that the blocked isocyanate group formed is stable to active hydrogen at ambient temperature, but reactive to active hydrogen in the film-forming polymer at elevated temperatures, typically 90 ℃ to 200 ℃.

Suitable polyisocyanates include aromatic and aliphatic polyisocyanates, including cycloaliphatic polyisocyanates, and representative examples include 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, mixtures of phenylmethane-4, 4' -diisocyanate and polymethylene polyphenylisocyanate. Higher polyisocyanates such as triisocyanates can be used. Examples would include triphenylmethane-4, 4',4 "-triisocyanate. Prepolymers of isocyanate () -with polyols such as neopentyl glycol and trimethylolpropane and prepolymers with polymeric polyols such as polycaprolactone diols and triols (NCO/OH equivalent ratio greater than 1) may also be used.

The polyisocyanate curing agent is typically used with the active hydrogen-containing cationic electrodepositable resin in an amount of from 5% to 60% by weight, such as from 20% to 50% by weight, based on the total weight of resin solids of the electrodepositable composition.

In certain embodiments, the coating composition comprising the film-forming resin further comprises yttrium. In certain embodiments, yttrium is present in such compositions in an amount of 10 to 10000ppm, such as no greater than 5000ppm, and in some cases no greater than 1000ppm total yttrium (measured as elemental yttrium).

Both soluble and insoluble yttrium compounds may serve as yttrium sources. Examples of yttrium sources suitable for use in the lead-free electrodepositable coating composition are soluble organic and inorganic yttrium salts such as yttrium acetate, yttrium chloride, yttrium formate, yttrium carbonate, yttrium sulfamate, yttrium lactate, and yttrium nitrate. Yttrium nitrate, a readily available yttrium compound, is a preferred source of yttrium when yttrium is added to the electrocoat bath as an aqueous solution. 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 metal may also be used. When yttrium is intended to be incorporated into the electrocoat bath as a component of the pigment paste, yttrium oxide is often the preferred source of yttrium.

The electrodepositable compositions described herein are in the form of an aqueous dispersion. The term "dispersion" is believed to be a two-phase transparent, translucent or opaque resin system in which the resin is in the dispersed phase and water is in the continuous phase. The average particle size of the resinous phase is typically less than 1.0 and typically less than 0.5 microns, often less than 0.15 microns.

The concentration of the resin 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 compositions are in the form of resin concentrates, they typically have a resin solids content of from 20 to 60 percent by weight, based on the weight of the aqueous dispersion.

The electrodepositable compositions described herein are often provided as a two-component: (1) a transparent resin supply comprising an ionic electrodepositable resin, typically containing active hydrogen, i.e., a primary film-forming polymer, a curing agent, and any additional water-dispersible, non-pigmented components; and (2) a pigment paste, which typically includes one or more pigments, a water-dispersible grinding resin (which may be the same as or different from the primary film-forming polymer), and optional additives such as wetting agents or dispersing aids. Electrodeposition bath components (1) and (2) are dispersed in an aqueous medium, which comprises water and typically a coalescing solvent.

As previously mentioned, the aqueous medium may contain a coalescing solvent in addition to water. Useful coalescing solvents are often hydrocarbons, alcohols, esters, ethers and ketones. Preferred coalescing solvents are often alcohols, polyols and ketones. Specific coalescing solvents include isopropanol, butanol, 2-ethylhexanol, isophorone, 2-methoxypentanone, ethylene glycol and propylene glycol, and the monoethyl monobutyl and monohexyl ethers of ethylene glycol. The amount of coalescing solvent is generally from 0.01 to 25%, 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 film-forming resin-containing coating composition. As used herein, the term "colorant" means any substance that is capable of imparting color and/or other opacity and/or other visual effect to a composition. The colorant can be added to the composition in any form, such as 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 toners, such as those used in the paint industry and/or listed in the Dry Color Manufacturers Association (DCMA), as well as special effect compositions. The colorant may comprise, for example, a finely divided solid powder which is insoluble, but wettable under the conditions of use. The colorant may be organic or inorganic and may be aggregated or non-aggregated. The colorant may be incorporated using a grinding media such as an acrylic grinding carrier, the use of which is familiar to those skilled in the art.

Exemplary pigments and/or pigment compositions include, but are not limited to, carbazole dioxazine crude pigment, azo, monoazo, disazo, naphthol AS, salt types (lakes), benzimidazolone, concentrates, metal complexes, isoindolinone, isoindoline and polycyclic phthalocyanine, quinacridone, perylene, perinone orange, diketopyrrolopyrrole, thioindigo, anthraquinone, indanthrone, anthrapyrimidine, flavanthrene, pyranthrone, anthanthrone, 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, but are not limited to, those that are solvent-based and/or water-based, such as phthalocyanine green or blue, iron oxide, bismuth vanadate, anthrone, perylene, aluminum, and quinacridone.

Exemplary hueing agents include, but are not limited to, pigments dispersed in an aqueous-based or water-miscible vehicle, such as AQUA-CHEM896 commercially available from Degussa, Inc, charismacolor and MAXITONER inclusion color commercially available from AccurateDispersions division of Eastman Chemical, Inc.

As noted above, the colorant can be in the form of a dispersion, including but not limited to a nanoparticle dispersion. Nanoparticle dispersions can include one or more highly dispersed nanoparticle colorants and/or colorant particles that produce a desired visible color and/or opacity and/or visual effect. The nanoparticle dispersion may include a colorant such as a pigment or dye having a particle size of less than 150nm, for example less than 70nm or less than 30 nm. Nanoparticles can be produced by milling a starting organic or inorganic pigment with milling media having a particle size of less than 0.5 mm. Exemplary nanoparticle dispersions and methods for their manufacture are shown in U.S. patent No.6875800B2, which is incorporated herein by reference. Nanoparticle dispersions can also be produced by crystallization, precipitation, gas phase condensation, and chemical attrition (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, a "dispersion of resin-coated nanoparticles" refers to a continuous phase in which are dispersed discrete "composite microparticles" comprising nanoparticles and a resin coating on the nanoparticles. Exemplary dispersions of resin-coated nanoparticles and methods for making them are shown in U.S. patent application publication 2005-0287348A1, filed 24.6.2004, U.S. provisional application No.60/482167, filed 24.6.2003, and U.S. patent application Serial No.11/337062, filed 20.1.2006, which are also incorporated herein by reference.

Exemplary special effect compositions that can be used include pigments and/or compositions that produce one or more appearance effects such as reflectance, pearlescence, metallic sheen, phosphorescence, fluorescence, photochromism, photosensitivity, thermochromism, goniochromism and/or discoloration. Additional special effect compositions may provide other perceptible properties, such as opacity or texture. In certain embodiments, special effect compositions can produce a color transition such that the color of the coating changes when the coating is viewed at different angles. Exemplary color effect compositions are shown in U.S. patent No.6894086, which is incorporated herein by reference. Additional color effect compositions may include transparent coated mica and/or synthetic mica, coated silica, coated alumina, transparent liquid crystal pigments, liquid crystal coatings, and/or any composition in which interference is caused by refractive index differences in the material, rather than by refractive index differences between the surface of the material and air.

In certain embodiments, photosensitive compositions and/or photochromic compositions (which reversibly change its color when exposed to one or more light sources) can be used in the present invention. Photochromic and/or photosensitive compositions can be activated by exposure to radiation of a particular wavelength. When the composition becomes excited, the molecular structure changes and the changed structure exhibits a new color that is different from the original color of the composition. Upon removal of exposure to radiation, the photochromic and/or photosensitive composition can return to a resting state, in which it returns to the original color of the composition. In certain embodiments, the photochromic and/or photosensitive composition can be colorless in the unactivated state and exhibit a color in the activated state. Full color change can occur in milliseconds to minutes, such as 20 seconds to 60 seconds. Exemplary photochromic and/or photosensitive compositions include photochromic dyes.

In certain embodiments, the photosensitive composition and/or photochromic composition can be linked to and/or at least partially bonded (e.g., by covalent bonding) to a polymer and/or polymeric material of the polymerizable component. In contrast to some coatings, in which the photosensitive composition migrates out of the coating and crystallizes into the substrate, according to certain embodiments of the present invention, the photosensitive composition and/or photochromic composition attached to and/or at least partially bonded to the polymer and/or polymerizable component has minimal coating migration. Exemplary photosensitive and/or photochromic compositions and methods for making them are shown in U.S. application Ser. No.10/892919 filed on 7, 16, 2004, which is incorporated herein by reference.

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

After deposition, the coating is often heated to cure the deposited composition. The heating or curing operation is often carried out at a temperature of 120-250 deg.C, such as 120-190 deg.C, for a time period of 10-60 minutes. In certain embodiments, the thickness of the formed film is 10 to 50 microns.

As will be appreciated from the foregoing description, the present invention relates to a method for coating a metal substrate comprising: (a) contacting the substrate with a pretreatment composition, and then (b) depositing a coating on the substrate, which is formed from a composition comprising a film-forming resin. These methods of the invention do not include depositing a zinc phosphate or zinc chromate containing coating onto the substrate.

Pretreatment compositions according to certain embodiments of the invention (based on zirconyl compounds) contain little or no free fluoride (fluoride). As a result, corrosion inhibiting compounds such as the rare earth elements described herein (which are insoluble when free fluoride ions are present in the pretreatment composition) are now soluble in the pretreatment compositions of the present invention. Coatings comprising zirconyl compounds and these rare earth elements exhibit surface morphologies that are significantly different from coatings based on zirconium and pretreatment compositions containing free fluoride ions. In addition, as demonstrated in the examples below, the corrosion resistance performed was at least as good or better than the pretreatment composition based on zirconium compounds with free fluoride ions and without rare earth metals. As defined herein, a pretreatment composition containing "little or no free fluoride" is a pretreatment composition having no more than 1ppm free fluoride (based on elemental fluoride).

For certain substrates, such as aluminum-containing substrates, in certain embodiments, a small amount of free fluoride ions may be included in the pretreatment composition to etch the surface of the aluminum-containing substrate. In these certain embodiments, however, the relative amount of free fluoride is such that limited complexation with the rare earth element occurs, and therefore limited insolubility in the rare earth metal complex formed. As defined herein, a pretreatment composition containing a "minor amount of free fluoride" is a pretreatment composition having from 2ppm to 30ppm, e.g., 25ppm, free fluoride (based on elemental fluoride).

As stated throughout the foregoing specification, the methods and coated substrates of the present invention do not include the deposition of heavy metal phosphates, such as zinc phosphate, or chromates, in certain embodiments. As a result, the environmental drawbacks associated with such materials are avoided. However, the process of the present invention has been shown to provide coated substrates whose corrosion resistance in at least some cases is at a comparable level, and in some cases even better, than the processes using such materials. This is a surprising and unexpected discovery of the present invention and meets a long-felt need in the art. In addition, the process of the present invention has been shown to avoid discoloration of subsequently applied coatings, such as certain non-black electrodeposited coatings.

The following examples illustrate the invention and are not to be considered as limiting the invention to their details. All parts and percentages in the examples, as well as throughout the specification, are by weight unless otherwise indicated.

Example 1

The following materials and coating compositions were prepared and evaluated using the following tests 1 and 2:

cleaning agent 1: chemkleen166HP/171ALF, alkaline cleaner

Cleaning agent 2: chemkleen2010LP/181ALP, alkaline cleaner

Pretreatment 1: CHEMFOS700(CF700AW)/CHEMSEAL59(CS59), impregnated with the trication Zn phosphate used and with a sealant, commercially available from PPG Industries, Inc.

And (3) pretreatment 2: zirconyl nitrate based pretreatment

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium) and washed withThe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (3) pretreatment: zirconyl nitrate based pretreatment with Cu

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 20ppm copper nitrate (as copper) was added, and the mixture was washed with waterThe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (4) pretreatment: zirconyl nitrate based pretreatment with cerium

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 50ppm cerium chloride (as cerium) was added, and the mixture was washed with waterThe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (5) pretreatment: zirconyl nitrate based pretreatment with praseodymium

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 50ppm praseodymium nitrate hexahydrate (as praseodymium) was added, and the mixture was diluted with water to a zirconium concentration of 200ppm (as zirconium), andthe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (6) pretreatment: zirconyl nitrate based pretreatment with addition of fluoride ions

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 0.10M ammonium bifluoride was added so that the free fluoride concentration measured with a fluoride ion selective electrode (9609BNWP Thermo Scientific) was 25ppm, andthe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (7) pretreatment: zirconyl nitrate based pretreatment with Cu and added fluoride ions

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 0.10M ammonium bifluoride was added so that the free fluoride concentration measured by a fluoride ion selective electrode (9609BNWP Thermo Scientific) was 25ppm, 20ppm of copper nitrate (as copper) was added, and the zirconium concentration was measured with a standard sample of zirconium nitrateThe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

And (3) pretreatment 8: zirconyl nitrate based pretreatment with yttrium

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 200ppm (as zirconium), 100ppm yttrium nitrate (as yttrium) was added, and the mixture was diluted with waterThe buffer adjusted the pH to 2.9. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

Pretreatment 9: zirconyl nitrate based pretreatment with hexafluorozirconic acid

The zirconium pretreatment solution was prepared as follows: zirconyl nitrate was diluted with water to a zirconium concentration of 100ppm (as zirconium), 100ppm hexafluorozirconic acid was added, and the mixture was diluted with waterThe buffer adjusted the pH to 4.4. After pretreatment in the zirconium pretreatment solution, the panels were rinsed thoroughly with deionized water and then dried with a warm air purge.

Paint 1: ED6060CZ, cathodic electrocoat, available from PPG Industries.

And (3) paint 2: amine catalyzed epoxy, according to military specification Mil-P-53022.

Test 1: 20 or 40 cycles of GM-9511P.

And (3) testing 2: GM-9540P for 40 cycles.

The coating system was cleaned using cleaner 1 or 2, rinsed with deionized water, and pre-treated (spray or dip) at 27 ℃ for 120 seconds. The panels were then rinsed with deionized water and dried using forced air at 55 ℃ for 5 minutes.

The exemplary coating (paint 1) composition was applied at 0.0008 to 0.0010 inches and cured in an electric oven at 175 ℃ for 25 minutes.

Example 1:

the performance of pre-treatment 1 was evaluated for resistance tests 1 and 2 relative to pre-treatments 2-8. The cold gadolinium plates (ACT panels) were cleaned using cleaner 1, rinsed with deionized water, and pre-treated (spray or dip coated) at 27 ℃ for 120 seconds. The panels were then rinsed with deionized water and dried using forced air at 55 ℃ for 5 minutes.

The pretreatment was evaluated as follows: they were applied by electrocoating, the paint films were cured, and they were then subjected to 40 cycles of hour/GM-9511P (test 1) and/GM-9540P (test 2). The panels were electrocoated with paint 1 composition to a dry film thickness of 0.0008 to 0.0010 inches and cured in an electric oven at 175 ℃ for 25 minutes.

The sample was then longitudinally scribed and subjected to 40 cycles of test 1 and test 2. Table 1 summarizes the corrosion performance of the different pretreatment compositions after these tests.

TABLE 1 corrosiveness

Example 2:

the performance of pre-treatment 1 for resistance tests 1 and 2 was evaluated relative to pre-treatments 2,4, 6 and 9. The cold gadolinium plates (ACT panels) were cleaned using cleaner 1, rinsed with deionized water, and pre-treated (spray or dip coated) at 27 ℃ for 120 seconds. The panels were then rinsed with deionized water and dried using forced air at 55 ℃ for 5 minutes.

The pretreatment was evaluated as follows: they were applied by electrocoating, the paint films were cured, and they were then subjected to 20 cycles of hour/GM-9511P (test 1) and GM-9540P (test 2). The panels were coated with the paint 2 composition, 0.0009-0.0011 inch dry film thickness, and allowed to cure for 7 days at ambient conditions.

The sample was then longitudinally scribed and placed in test 1 for 20 cycles.

TABLE 2 corrosiveness

Examination of the data table reveals that the performance of the pretreatment derived from the absence of F-and from the zirconyl complex behaves similar to the Zn-phosphate based pretreatment when electrocoated. The data table also shows that the performance from the pretreatment without F-and from the zirconyl complex behaves similar to the Zn phosphate based pretreatment when painted with amine catalyzed epoxy.

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

Claims (20)

1. A pretreatment composition for treating a metal substrate comprising: (a) a rare earth metal and (b) a zirconyl compound.

2. The pretreatment composition of claim 1, wherein the zirconyl compound (b) comprises zirconyl nitrate, zirconyl acetate, zirconyl carbonate, protonated zirconium basic carbonate, zirconyl sulfate, zirconium oxychloride, zirconium oxyiodide, zirconium oxybromide, or mixtures thereof.

3. The pretreatment composition of claim 1, further comprising: (c) an electropositive metal.

4. The pretreatment composition of claim 1, further comprising: (c) a group IVB and/or group VB metal.

5. The pretreatment composition of claim 3, further comprising: (d) a group IVB and/or group VB metal.

6. The pretreatment composition of claim 1, wherein the rare earth metal (a) comprises yttrium, praseodymium, cerium, or mixtures thereof.

7. The pretreatment composition of claim 1, wherein the source of the rare earth metal (a) comprises a rare earth metal compound.

8. The pretreatment composition of claim 7, wherein the rare earth metal compound comprises a compound of yttrium, cerium, praseodymium, or mixtures thereof.

9. The pretreatment composition of claim 1, wherein a ratio of zirconium from said zirconyl compound to said rare earth metal in the pretreatment composition is from 200/1 to 1/1.

10. The pretreatment composition of claim 1, wherein the amount of zirconium from the zirconyl compound in the pretreatment composition is from 10ppm to 5000 ppm.

11. The pretreatment composition of claim 1, wherein the pretreatment composition is substantially free of free fluoride ions.

12. A metal substrate treated with the pretreatment composition of claim 1.

13. A metal substrate treated with the pretreatment composition of claim 3.

14. A metal substrate treated with the pretreatment composition of claim 4.

15. A metal substrate treated with the pretreatment composition of claim 5.

16. The pretreatment composition of claim 3, wherein the amount of metal from said zirconyl compound and from said group IVB and/or group VB metal in the pretreatment composition is in the range of from 10ppm to 5000 ppm.

17. A method of treating a metal substrate comprising:

(a) the metal substrate is contacted with a pretreatment composition comprising a rare earth metal and a zirconyl compound.

18. The method of claim 17, wherein the pretreatment composition is contacted with the metal substrate without prior application of an electropositive metal.

19. The method of claim 17, wherein the pretreatment composition further comprises a group IVB and/or group VB metal and/or (d) an electropositive metal.

20. The method of claim 17, further comprising electrophoretically depositing a coating composition onto the metal substrate after step (a).