Non-chromated cobalt conversion coating method and coated articles

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a metal substrate, wherein said substrate is aluminum, aluminum alloy, magnesium, magnesium alloy, a Cd plated substrate, or a Zn plated substrate, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution comprising a soluble cobalt-III hexanitrite complex, wherein said cobalt-III hexanitrite complex is present in the form of Me.sub.3 [Co(NO.sub.2).sub.6 ] wherein Me is one or more selected from the group consisting of Na, K, and Li, and wherein said cobalt-III hexanitrite complex was made by reacting a cobalt-II salt with an alkali metal nitrite such that the concentration of said cobalt-III hexanitrite complex is from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexanitrite complex, and wherein said aqueous reaction solution has a pH of about 7.0 to 7.2;
• and
• (b) contacting said metal substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution comprising a soluble cobalt-III hexacoordinated complex, wherein said cobalt-III hexacoordinated complex is present in the form of Me.sub.3 [Co(NO.sub.2).sub.6 ] wherein Me is one or more selected from the group consisting of Na, K, and Li, and the concentration of said cobalt-III hexacoordinated complex is from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexacoordinated complex;
• and
• (b) contacting said metal substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting a cobalt-II salt with an alkali metal nitrite salt, wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon of final solution to the saturation limit of the cobalt-II salt employed and the concentration of said alkali metal nitrite salt is from about 0.6 to 12 moles per gallon of final solution;
• and
• (b) contacting said substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting cobalt nitrate, Co(NO.sub.3).sub.2.6H.sub.2 O, with sodium nitrite, NaNO.sub.2, wherein the concentration of said cobalt nitrate is from about 75 to 95 grams per gallon of final solution and the concentration of said sodium nitrite is from about 227 to 246 grams per gallon of final solution;
• and
• (b) contacting said substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A chemical conversion coating solution for producing a cobalt conversion coating on a metal substrate, said solution comprising an aqueous reaction solution of a soluble cobalt-III hexacoordinated complex, wherein said cobalt-III hexacoordinated complex is present in the form of Me.sub.3 [Co(NO.sub.2).sub.6 ] wherein Me is one or more selected from the group consisting of Na, K, and Li, the concentration of said cobalt-III hexacoordinated complex being from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexacoordinated complex, and wherein said cobalt conversion solution has a pH of about 7.0 to 7.2.

A chemical conversion coating solution for producing a cobalt conversion coating on a metal substrate, said solution comprising:

• (a) an aqueous reaction solution of a soluble cobalt-III hexanitrite complex, the concentration of said cobalt-III hexanitrite complex being from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexanitrite complex, and wherein said aqueous reaction solution has a pH of about 7.0 to 7.2;
• (b) wherein said aqueous reaction solution is prepared by reacting a cobalt-II salt with a metal nitrite salt, wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon of final solution to the saturation limit of the cobalt-II salt employed and the concentration of said metal nitrite salt is from about 0.6 to 12 moles per gallon of final solution.

A chemical conversion coating solution for producing a cobalt conversion coating on a substrate, wherein said substrate is aluminum or aluminum alloy, said solution comprising an aqueous reaction solution of a soluble cobalt-III hexacoordinated complex, wherein said cobalt-III hexacoordinated complex is present in the form of Me.sub.3 [Co(NO.sub.2).sub.6 ] wherein Me is one or more selected from the group consisting of Na, K, and Li, the concentration of said cobalt-III hexacoordinated complex being from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexacoordinated complex.

A chemical conversion coating solution for producing a cobalt conversion coating on a substrate, wherein said substrate is aluminum or aluminum alloy, said solution comprising:

• (a) an aqueous reaction solution of a soluble cobalt-III hexanitrite complex, the concentration of said cobalt-III hexanitrite complex being from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexanitrite complex;
• (b) wherein said reaction solution is prepared by reacting a cobalt-II salt with a metal nitrite salt, wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon of final solution to the saturation limit of the cobalt-II salt employed and the concentration of said metal nitrite salt is from about 0.6 to 12 moles per gallon of final solution.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting cobalt chloride, CoCl.sub.2.6H.sub.2 O, with sodium nitrite, NaNO.sub.2, wherein the concentration of said cobalt chloride is about 69 grams per gallon of final solution and the concentration of said sodium nitrite is about 242 grams per gallon of final solution;
• and
• (b) contacting said substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting cobalt acetate, Co(CH.sub.3 COO).sub.2.4H.sub.2 O, with sodium nitrite, NaNO.sub.2, wherein the concentration of said cobalt acetate is about 73 grams per gallon of final solution and the concentration of said sodium nitrite is about 242 grams per gallon of final solution;
• and
• (b) contacting said substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum or aluminum alloy, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution comprising a soluble cobalt-III hexanitrite complex, wherein said cobalt-III hexanitrite complex is present in the form of Me.sub.3 [Co(NO.sub.2).sub.6 ] wherein Me is one or more selected from the group consisting of Na, K, and Li, and wherein said cobalt-III hexanitrite complex was made by reacting a cobalt-II salt with an alkali metal nitrite such that the concentration of said cobalt-III hexanitrite complex is from about 0.1 mole per gallon of solution to the saturation limit of said cobalt-III hexanitrite complex;
• and
• (b) contacting said metal substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.

A process for forming an oxide film cobalt conversion coating exhibiting corrosion resistance and paint adhesion properties on a substrate, wherein said substrate is aluminum, aluminum alloy, magnesium, magnesium alloy, a Cd plated substrate, or a Zn plated substrate, said process comprising the steps of:

• (a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting a cobalt-II salt with an alkali metal nitrite salt, wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon of final solution to the saturation limit of the cobalt-II salt employed and the concentration of said alkali metal nitrite salt is from about 0.6 to 12 moles per gallon of final solution, and wherein said aqueous reaction solution has a pH of about 7.0 to 7.2;
• and
• (b) contacting said substrate with said solution for a sufficient amount of time to oxidize the surface of said substrate, whereby said oxide film cobalt conversion coating is formed, thereby imparting corrosion resistance and paint adhesion properties to said substrate.