KR20010113920A - Weldable, coated metal substrates and methods for preparing and inhibiting corrosion of the same - Google Patents

Abstract

The present invention provides a weldable and coated surface having a weldable coating whose surface is pretreated with a Group IIIB or Group IVB metal compound or mixtures thereof, and wherein the conductive pigment is dispersed through a binder deposited on at least a portion of the pretreatment coating composition. Provided is a metal substrate.

Description

Weldable and coated metal substrate, preparation method thereof and corrosion inhibiting method thereof {WELDABLE, COATED METAL SUBSTRATES AND METHODS FOR PREPARING AND INHIBITING CORROSION OF THE SAME}

Weldable coatings containing an electrically conductive material, such as zinc, are often used to provide an electrically conductive layer on a metal substrate. Zinc rich weldable coatings can be applied directly to or on ferrous metal surfaces treated with chromium-containing solutions. For example, US Pat. No. 4,346,143 discloses a method of providing corrosion resistance to ferrous metal substrates comprising etching a surface of the substrate with nitric acid and then applying a zinc-rich coating, including a binder, to the etched surface. .

US Pat. Nos. 4,157,924 and 4,186,036 disclose weldable coatings for metal substrates containing epoxy or phenoxy resins, electrically conductive pigments such as zinc and diluents such as glycol ethers. As discussed in column 7, lines 37 to 42, the substrate can be pretreated with a powdered metal-free composition containing chromate and / or phosphate ions.

Similarly, European patent application 0157392 discloses a corrosion resistant primer for metal phosphate- or chromate-treated steel consisting of a mixture of 70 to 95% by weight zinc, aluminum, lubricants and binders.

U. S. Patent No. 3,687, 739 discloses a weldable comprising a topcoat comprising (1) an undercoating of a powdered metal and a hexavalent chromium-containing liquid composition and (2) particulate electrically conductive pigments and binders. Composite coatings are disclosed.

Chromium-containing coatings provide good corrosion resistance, especially under zinc-rich coatings, but are toxic and exhibit disposal problems. Thus, there is a need for a chromium-free treatment solution for treating metal substrates prior to application of the weldable coating. The treatment solution must provide corrosion resistance and maintain the substrate electrical conductivity for welding.

Summary of the Invention

One aspect of the invention is a metal substrate; (b) a pretreatment composition comprising a Group IIIB or IVB metal compound or a mixture thereof deposited on at least a portion of the surface of the metal substrate; And (c) a weldable coating comprising an electrically conductive pigment dispersed through a binder deposited on at least a portion of the pretreatment composition.

Another aspect of the invention is a method of forming a substrate having a pretreated surface comprising (a) treating the surface of the metal substrate with a pretreatment composition comprising a Group IIIB or Group IVB metal compound or mixture thereof; And (b) applying a weldable coating composition comprising an electrically conductive pigment and a binder to the pretreated surface to form a weldable and coated metal substrate. .

The present invention relates generally to coated metal substrates that are weldable and corrosion resistant, and more particularly to metal substrates having chromium-free coatings that inhibit corrosion and promote the formation and welding of metal substrates.

Unless otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used in the specification and claims are to be understood as being controlled in all cases by the term "about."

Metal substrates used in the practice of the present invention include ferrous metals, nonferrous metals, and combinations thereof. Suitable ferrous metals include iron, steel and alloys thereof. Non-limiting examples of useful steel materials include cold rolled steel, galvanized steel, galvanized steel, stainless steel, pickled steel, zinc-iron alloys such as GALVANNEAL, and combinations thereof. Include. Useful non-ferrous metals include aluminum, zinc, magnesium and alloys thereof. Combinations or composites of ferrous and nonferrous metals such as GALVALUME and GALFAN zinc-aluminum alloys may also be used.

The shape of the metal substrate may be a sheet, plate, bar, rod or any desired shape. Preferably, the shape of the metal substrate is a long strip that wraps around the spool in coil form. The thickness of the strip is preferably about 0.254 to about 3.18 mm (about 10 to about 125 mils), more preferably about 0.3 mm, although the thickness may be somewhat larger or smaller than desired. The butterfly of the strip generally can vary from about 30.5 to about 183 cm (about 12 to about 72 inches), although the butterfly may vary depending on its intended use.

Prior to depositing a coating on the surface of the metal substrate, it is desirable to remove foreign material from the metal surface by vigorously washing and degreasing the surface. The surface of the metal substrate may be cleaned by physical or chemical means, such as mechanically polishing or cleaning / degreasing with commercially available alkaline or acidic cleaners such as sodium metasilicate and sodium hydroxide, which are well known in the art. . A non-limiting example of a preferred cleaner is CHEMKLEEN 1633, an alkaline cleaner, commercially available from PPG Pretreatment and Specialty Products, Troy, Michigan.

Following the washing step, the metal substrate is typically washed with water to remove any residue. The metal substrate can be briefly exposed to high temperatures or passed through rubber cleaner rolls to allow water to dry and air dry using an air knife.

In the present invention, the pretreatment coating composition is deposited on at least a portion of the outer surface of the metal substrate. Preferably, the entire outer surface of the metal substrate is treated with the pretreatment composition.

The pretreatment composition facilitates subsequent adhesion of the weldable coating composition to the metal substrate. Such a pretreatment coating provides a welding tool to provide an electrically conductive path through which at least a portion of the electrically conductive pigments in the weldable coating can be in contact with or in essence contact with the metal substrate through the pretreatment coating. It must be thin and / or deformable enough to allow heat and force to be applied to the weldable coating. As used herein, “essentially contacted” means that the electrical resistance provided by the pretreatment coating is less than about 1 Ω. The thickness of the pretreatment film varies but is generally less than about 1 μm, preferably about 1 to about 500 nm, and more preferably about 10 to about 300 nm.

The pretreatment composition comprises one or more Group IIIB or IVB element-containing compounds or mixtures thereof dissolved or dispersed in a carrier medium, generally an aqueous medium. Group IIIB and IVB elements are defined by the CAS Element Periodic Table, as shown, for example, in Handbook of Chemistry and Physics, (60th Ed. 1980). Transition metal compounds and rare earth metal compounds are compounds of zirconium, titanium, hafnium, yttrium and cerium and mixtures thereof. Typical zirconium compounds include hexafluorozirconic acid, alkali metals and ammonium salts thereof, ammonium zirconium carbonate, zirconyl nitrate, zirconium carboxylate and zirconium hydroxy carboxylate (e.g. hydrofluorozirconic acid), zirconium acetate, zirconium oxal Latex, ammonium zirconium glycolide, ammonium zirconium lactate, ammonium zirconium citrate, and mixtures thereof. Preference is given to hexafluorozirconic acid. An example of a yttrium compound is yttrium nitrate. Examples of titanium compounds are fluorotitanic acid and salts thereof. An example of a hafnium compound is hafnium nitrate. An example of a cerium compound is serosnitrate. Preferably, the Group IIIB or IVB metal compound is in the form of a metal salt or acid that is water soluble.

Group IIIB or IVB metal compounds are generally present in the carrier medium in amounts of 10 to 5000 ppm metal, preferably 100 to 300 ppm metal.

In addition, the pretreatment composition carrier may contain a film forming resin. Suitable resins include reaction products of one or more alkanolamines and epoxy-functional materials containing two or more epoxy groups as disclosed, for example, in US Pat. No. 5,653,823. Preferably such resins contain beta hydroxy esters, imides or sulfide functional groups, phthalimides, or mercaptoglycerins as additional reactants in the preparation of the resins introduced using dimethylolpropionic acid. Optionally, the reaction product is a diglycidyl ether of bisphenol A (EPON 880 available from Shell Chemical Company), dimethylol propionic acid, and 0.6 to 5.0: 0.05 to 5.5: 1 of diethanolamine. Molar ratio of reaction product. Other suitable resins include water soluble and water dispersible polyacrylic acids as disclosed in US Pat. Nos. 3,912,548 and 5,328,525; Phenol-formaldehyde resins as disclosed in US Pat. No. 5,662,746, which is incorporated herein by reference; Water soluble polyamides as disclosed in WO 95/33869; Copolymers of allyl ether with maleic or acrylic acid as disclosed in Canadian Patent Application No. 2,087,352; And water-soluble and water-dispersible resins including epoxy resins, aminoplasts, phenol-formaldehyde resins, tannins, and polyvinyl phenols as disclosed in US Pat. No. 5,449,415.

In an embodiment of the invention, the film forming resin is present in the pretreatment coating composition in an amount of 0.005% to 30% based on the total weight of the pretreatment composition, and the Group IIIB or IVB metal compound is 10 based on the total weight of the pretreatment composition. To 5000, preferably in amounts of 100 to 1000 ppm metal. The weight ratio of the resin to the Group IIIB or IVB metal or metal compound is 2.0 to 10.0, preferably 3.0 to 5.0, based on the metal.

The pretreatment coating composition may further comprise a surfactant that acts as an adjuvant to enhance the wettability of the substrate. Generally, the surfactant material is present in an amount of less than about 2 weight percent based on the total weight of the pretreatment coating composition. Other optional materials in the carrier medium include surfactants that act as antifoams or substrate wetting agents.

Preferably, the pretreatment coating composition is essentially free of chromium-containing materials, ie contains less than about 2 weight percent, more preferably less than about 0.05 weight percent chromium-containing material (represented as CrO ₃ ). Examples of such chromium-containing materials include chromic acid, chromium trioxide, chromic anhydride, dichromate salts such as ammonium dichromate, sodium dichromate, potassium dichromate and calcium, barium, magnesium, zinc, cadmium and strontium dichromate do. Most preferably, the pretreatment coating composition does not contain chromium-containing materials.

The pretreatment coating composition is applied to the surface of the metal substrate by any conventional application technique such as spraying, impregnation or roll coating in a batch or continuous manner. The temperature of the pretreatment coating composition when applied is generally about 10 to about 85 ° C, preferably about 15 to about 60 ° C. The pH of the preferred pretreatment coating composition in application is generally from about 2.0 to about 5.5, preferably from about 3.5 to about 5.5. The pH of the medium may be selected from inorganic acids such as hydrofluoric acid, fluoroboric acid, phosphoric acid and mixtures thereof; Organic acids such as lactic acid, acetic acid, citric acid, sulfamic acid or mixtures thereof; And water soluble or water insoluble bases such as sodium hydroxide, ammonium hydroxide, ammonia, or amines such as triethylamine, methylethyl amine, or mixtures thereof.

Continuous processes are commonly used in the coil coating industry and also for mill applications. The pretreatment coating composition can be applied by any conventional method. For example, in the coil industry, substrates are cleaned and cleaned and then contacted with the pretreatment coating composition, typically by roll coating with chemical coatings. The treated strip is then heated, painted and baked by conventional coil coating methods.

Mill application of the pretreatment composition can be achieved by applying impregnation, spraying or roll coating to the newly produced metal strip. Excess pretreatment composition is generally removed by ringer rolls. After the pretreatment composition is applied to the metal surface, the metal is washed with deionized water and dried at room temperature or dried at elevated temperature to remove excess moisture from the treated substrate surface and to cure any curable coating components to prepare a pretreatment coating. . Optionally, the treated substrate is heated at about 65 to 125 ° C. for about 2 to about 30 seconds to form a coated substrate having dried residues of the pretreatment coating composition formed thereon. If the substrate has already been heated from the hot melt manufacturing process, the treated substrate does not need to be heated to promote drying after application. The temperature and time to dry the coating will vary depending on such variables as the percentage of solids in the coating, the components of the coating composition and the type of substrate.

The amount by which the residue of the pretreatment composition covers the film is generally about 1 to about 1000 mg / m ² , and preferably about 10 to about 400 mg / m ² .

In the present invention, a weldable coating composition is deposited on at least a portion of the pretreatment coating. The weldable coating composition comprises a binder that provides electroconductive and cathodic protection to the weldable coating and one or more electroconductive pigments dispersed through one or more binders that adhere the electroconductive pigment to the pretreatment coating.

Non-limiting examples of suitable electroconductive pigments include zinc (preferred), aluminum, iron, graphite, ferric phosphide and mixtures thereof. Preferred zinc particles are commercially available as ZINCOLI S 620 or 520 from ZINCOLI GmbH. The average particle size (same diameter of the sphere) of the electroconductive pigment particles is about 10 μm, preferably about 1 to about 5 μm, and more preferably about 3 μm.

Since the metal substrate is subsequently welded, the weldable coating composition generally contains a significant amount of the electrically conductive pigments of at least about 10% by volume, preferably from about 30 to about 60% by volume, based on the total volume of the electrically conductive pigments and binder. It must be present in an amount of.

Binders are present to stabilize the electrically conductive pigments in the pretreatment coating. Preferably, the binder generally forms a continuous film when applied to the surface of the pretreatment coating. Generally, about 5 to about 50 weight percent, preferably about 10 to about 30 weight percent, more preferably about 10 to about 20 weight percent of the weldable coating composition on a total solids basis.

Binders may include oligomeric binders, polymeric binders, and mixtures thereof. The binder is preferably a dendritic polymeric binder selected from thermosetting binders, thermoplastic binders or mixtures thereof. Non-limiting examples of suitable thermosetting materials include polyesters, epoxy-containing materials, phenoxy-containing materials, polyurethanes, and mixtures thereof with crosslinkers such as aminoplasts or isocyanates described below. Non-limiting examples of suitable thermoplastic binders include polymeric epoxy resins, defunctionalized epoxy resins, vinyl polymers, polyesters, polyolefins, polyamides, polyurethanes, acrylic polymers, and mixtures thereof. Examples of useful binders include phenoxy polyether polyols and inorganic silicates.

Particularly preferred binders are polyglycidyl ethers of polyhydric phenols having an average molecular weight of at least about 2000, preferably from about 5000 to about 100,000. These materials can be epoxy functionalized or defunctionalized by reacting epoxy groups with phenolic materials. Such binders may have an epoxy equivalent of about 2000 to about 1,000,000. Non-limiting examples of useful epoxy resins are commercially available from Shell Chemical Company as EPON® epoxy resins. Preferred EPON® epoxy resins include EPON® 1009 having an epoxy equivalent of about 2300 to 3800. Useful epoxy defunctionalized resins include phenoxy resins such as EPONOL resin 55-BK-30, commercially available from the shell.

Suitable crosslinkers or curing agents are disclosed in US Pat. No. 4,346,143, column 5, lines 45-62, and are blocked or unblocked di- or polyisocyanates such as DESMODUR® BL 1265, ie caprolactam Blocked toluene diisocyanate (commercially available from Bayer)] and aminoplasts such as etherified derivatives of urea-melamine- and benzoguanamine-formaldehyde condensates (trade name CYMEL from CYTEC Industries) (Trademark) and sold under the trade name RESIMENE (R) from Solutia.

Preferably, the weldable coating composition includes one or more diluents to adjust the viscosity of the composition so that it can be applied to a metal substrate by conventional coating techniques. Diluents should be chosen so as not to adversely affect the adhesion of the weldable coating to the pretreatment coating on the metal substrate. Suitable diluents include ketones such as cyclohexanone (preferably), acetone, methyl ethyl ketone, methyl isobutyl ketone and isophorone; 2-ethoxyethyl acetate, propylene glycol monomethyl ether (such as DOWANOL PM), dipropylene glycol monomethyl ether (such as DOWANOL DPM) or propylene glycol methyl ether acetate (such as Dow Chemical) PM ACETATE); And aromatic solvents such as aromatic solvent blends derived from mineral oils such as toluene, xylene, SOLVESSO®. The amount of diluent varies depending on the coating method, binder component and ratio of pigment to binder, but is generally about 10 to about 50 weight percent based on the total weight of the weldable coating composition.

Weldable coating compositions include phosphorus-containing materials such as metal phosphates or organophosphates as described above; Inorganic lubricants such as GLEITMO 1000S molybdenum disulfide particles commercially available from Fuchs, Germany; Extender pigments such as iron oxide and iron phosphide; Flow regulators; Thixotropes such as silica, montmorillonite clay and hydrogenated cartor oils; Antisettling agents such as aluminum stearate and polyethylene powder; Dehydrating agents that inhibit gas formation, such as silica, lime or sodium aluminum silicate; And optional ingredients such as wetting agents, including salts of sulfided cartor oil derivatives such as DEHYSOL R. .

Corrosion inhibition including carbon black, iron oxide, magnesium silicate (talc), zinc oxide, and molybdate such as zinc phosphate and calcium molybdate, zinc molybdate, barium molybdate and strontium molybdate and mixtures thereof Weldable coating compositions such as pigments. Generally, these optional components comprise less than about 20 weight percent, typically about 5 to about 15 weight percent, of the weldable coating composition on a total solids basis. Preferably, the weldable coating composition is essentially free of chromium-containing material, ie contains less than about 2% by weight of chromium-containing material and more preferably no chromium-containing material.

Preferred weldable coating compositions include EPON® 1009 epoxy-functional resins, zinc dust, salts of sulfided cartor oil derivatives, silica, molybdenum disulfide, red iron oxide, toluene diisocyanate blocked with caprolactam, melamine resin Dipropylene glycol methyl ether, propylene glycol methyl ether acetate, and cyclohexanone.

The weldable coating composition may be any conventional method well known in the art, such as dip coating, direct roll coating, reverse roll coating, curtain coating, air and airless spraying, electrostatic spraying, pressure spraying, rotary brush coating. It can be applied to the surface of the pretreatment coating by brushing such as or a combination of any of the techniques discussed above.

The thickness of the weldable coating varies depending on the application for which the coated metal substrate is to be introduced. In general, in order to achieve sufficient corrosion resistance to coil metals for automotive applications, the weldable coating applied is at least about 1 μm (about 0.5 mils), preferably about 1 to about 20 μm, more preferably about 2 to about It should have a thickness of about 5 μm. For substrates and other applications, thinner or thicker coatings may be used.

After application, the weldable coating is preferably dried and / or any curable components thereof cured to form dried residues of the weldable coating on the substrate.

The dried residue may be formed at elevated temperatures in the peak metal temperature range of less than about 300 ° C. Many such binders made from epoxy-containing materials require curing at elevated temperatures for a period of time sufficient to evaporate any diluent in the coating and to cure or solidify the binder. In general, the baking temperature will depend on the film thickness and the components of the binder. For preferred binders made from epoxy-containing mulles, peak metal temperatures of about 150 to about 300 ° C. are preferred.

After the weldable coating is dried and / or cured, the metal substrate is stored or sent to other operations such as forming, forming, cutting and / or welding operations to form the substrate into parts such as fenders or doors and / or Or to subsequent electrocoating or top coat. While the metal is introduced into storage, transport or subsequent operations, the coating protects the metal surface from corrosion, for example white and red rust, resulting from exposure to the atmospheric environment.

Since the coated metal substrate prepared according to the invention is electrically conductive, the top coat of the coated substrate by electrodeposition is of great importance. Compositions and methods for electrodeposition coatings are well known in the art and are not deemed necessary for further discussion. Useful compositions and methods are disclosed in US Pat. Nos. 5,530,043 (associated with anionic electrodeposition) and US Pat. Nos. 5,760,107, 5,820,987 and 4,933,056 (associated with cationic electrodeposition).

The weldable coated metal substrate may optionally be coated with a metal phosphate coating, for example zinc phosphate deposited on at least a portion of the weldable coating.

Application methods and compositions for such metal phosphate coatings are disclosed in US Pat. Nos. 4,941,930 and 5,238,506.

The present invention is now described by the following specific, non-limiting examples. All parts and percentages are by weight unless otherwise indicated.

The following examples demonstrate the application of group IVB or IIIB elements to steel substrates and the use of surface treatments subsequently coated with a weldable coating according to the invention.

Preparation and Coating of Substrate

Electrozinc plating and hot-immersed galvanized steel substrates used for coating and testing are provided by USX.

Each panel is about 10.16 cm (4 in) wide, about 30.48 cm (12 in) long, and about 0.76 to 0.79 mm (0.030 to 0.031 in) thick. The steel panels were introduced into the alkaline cleaning process by spraying with 2 vol% of a bath of CHEMKLEEN 163, commercially available from PPG Industries, Inc., at a temperature of 60 ° C. (140 ° F.) for 60 seconds. The panels were removed from the alkaline wash bath and washed with water (about 21 ° C. (70 ° F.)) for 15 seconds at room temperature and dried with a warm air blower.

The panel was treated with one of the following pretreatment coatings: fluorozirconic acid solution containing 100 ppm Zr at pH 3.75 (Example 1) or fluorozirconic acid solution containing 1000 ppm Zr at pH 3.79 (Example 2). . All pretreatment solutions were applied at a rate of 3.4 × 10 ⁵ Pa (50 psi) and 56.4 m / min (185 ft / min) via roll coating application. The panels were immediately baked for 15 seconds to a peak metal temperature of 110 ° C ± 6 ° C (230 ° F ± 10 ° F). After drying, all panels were zinc-rich, epoxy resin-containing weldable coatings, ie BONAZINC 3001 (available from Fiji Industries, Inc.) on both sides of the panel using # 12 drawbars. It was applied (creating a dried film thickness of 3.0-4.0 μm) and baked for about 40-50 seconds until a peak metal temperature of 254 ° C. (490 ° F.) was reached at 390 ° C. (735 ° F.). The panel was then cooled at ambient temperature.

Corrosion test

Corrosion performance was measured by introducing the coated panels into the General Motors 9511P cyclic corrosion test. The relative evaluation according to the percentage of red rust formed on the overall tested surface of the panel is shown in Table 1 below.

Corrosion results from GM 9511P test (8 cycles) Substrate tested process % ^{1 of} red rust (degree of white pollution) USX EZG-60G Two-Sided Electrogalvanized Steel Example 1 0 (very cloudy) USX EZG-60G Two-Sided Electrogalvanized Steel Example 2 0 (very cloudy) USX HDA Zn / Fe-A45 Two-sided Hot Dipped Galvanized Steel Example 1 5 (cloudy) USX HDA Zn / Fe-A45 Two-sided Hot Dipped Galvanized Steel Example 2 5 (cloudy) ¹ Based on average of two panels

The pretreatment coatings and weldable coatings provide the metal substrates of the present invention with improved adhesion and flexibility and resistance to moisture, salt spray corrosion and the components of the coating subsequently applied. In addition, problems associated with the use of chromium and disposal have been reduced or eliminated.

Claims (25)

(a) a metal substrate; (b) a pretreatment composition comprising a Group IIIB or IVB metal compound or a mixture thereof deposited on at least a portion of the surface of the metal substrate; And (c) a weldable coating comprising an electrically conductive pigment dispersed through a binder deposited on at least a portion of the pretreatment composition Weldable and coated metal substrate comprising a. The method of claim 1, A coated metal substrate, wherein the metal substrate comprises iron metal. The method of claim 2, A coated metal substrate wherein said ferrous metal is selected from the group consisting of iron, steel and alloys thereof. The method of claim 3, wherein A coated metal substrate wherein the iron metal comprises steel selected from the group consisting of cold rolled steel, galvanized steel, electrogalvanized steel, stainless steel, and combinations thereof. The method of claim 1, A coated metal substrate comprising a metal other than iron selected from the group consisting of aluminum, zinc, magnesium and alloys thereof. The method of claim 1, A coated metal substrate, wherein said Group IIIB or IVB metal compound is a zirconium compound. The method of claim 6, A coated metal substrate, wherein the zirconium compound is hexafluorozirconic acid. The method of claim 1, A coated metal substrate wherein said pretreatment coating composition further comprises a film forming resin. The method of claim 1, A coated metal substrate, wherein said Group IIIB or IVB metal compound is present in an aqueous medium. The method of claim 1, A coated metal substrate wherein said pretreatment composition is essentially free of chromium-containing materials. The method of claim 1, A coated metal substrate wherein said electrically conductive pigment is selected from the group consisting of zinc, aluminum, iron, graphite, ferric phosphide and mixtures thereof. The method of claim 1, A coated metal substrate wherein said binder is selected from the group consisting of oligomeric binders, polymeric binders, and mixtures thereof. The method of claim 1, A coated metal substrate wherein said binder is selected from the group consisting of thermosetting binders, thermoplastic binders and mixtures thereof. The method of claim 13, A coated metal substrate wherein the binder comprises a thermosetting binder selected from the group consisting of polyesters, epoxy-containing materials, phenoxy-containing materials, aminoplasts, polyurethanes, and mixtures thereof. The method of claim 14, A coated metal substrate comprising an epoxy-containing material wherein the binder is a polyglycidyl ether of bisphenol A. The method of claim 13, A coated metal substrate wherein said binder comprises a thermoplastic binder selected from the group consisting of vinyl polymers, polyesters, polyolefins, polyamides, polyurethanes, acrylic polymers, and mixtures thereof. The method of claim 14, Wherein said weldable coating further comprises a crosslinking agent for crosslinking the thermosetting binder. The method of claim 1, A coated metal substrate wherein the weldable coating further comprises a phosphorus-containing material. The method of claim 1, A coated metal substrate wherein the weldable coating further comprises an inorganic lubricant. The method of claim 19, A coated metal substrate, wherein said inorganic lubricant is molybdenum disulfide. The method of claim 1, The coated metal substrate further comprising a metal phosphate coating deposited on at least a portion of the weldable coating composition. The method of claim 1, The coated metal substrate further comprising an electrodeposited coating deposited on at least a portion of the weldable coating. (a) treating the surface of the metal substrate with a pretreatment composition comprising a Group IIIB or Group IVB metal compound or mixtures thereof to form a substrate having a pretreated surface; And (b) applying a weldable coating composition in which an electroconductive pigment is dispersed through a binder to the pretreated surface to form a weldable and coated metal substrate. . The method of claim 23, And an initial step of washing the surface of the metal substrate with the cleaning composition prior to treatment with the pretreatment composition. The method of claim 23, The method further comprises the step of heating the coated metal substrate after applying the weldable composition in step (b).