US 5,298,092 A · Non-chromated oxide coating for aluminum substrates

Abstract

(A.) A process for forming a cobalt conversion coating on a metal substrate, thereby imparting corrosion resistance and paint adhesion properties. The invention was developed as a replacement for the prior art chromic acid process. The process includes the steps of: (a) providing a cobalt conversion reaction solution comprising an aqueous, alkaline solution containing a soluble cobalt-III hexacoordinated complex, the concentration of the cobalt-III hexacoordinated complex being from about 0.1 mole per gallon of solution to the saturation limit of the cobalt-III hexacoordinated complex; and (b) contacting the substrate with the aqueous reaction solution for a sufficient amount of time, whereby the cobalt conversion coating is formed. The substrate may be aluminum or aluminum alloy, as well as Cd plating, Zn plating, Zn-Ni plating, and steel. The cobalt-III hexacoordinated complex may be present in the form of [Co(NH.sub.3).sub.6 ]X.sub.3 wherein X is Cl, Br, NO.sub.3, CN, SCN, Y.sub.3 PO.sub.4, SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or Y.sub.2 CO.sub.3.

Claims51

Dependent claims

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

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous, alkaline reaction solution comprising a soluble cobalt-III hexammine complex, where said cobalt-III hexammine complex is present in the form of (Co(NH.sub.3).sub.6)X.sub.3, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and where said cobalt-III hexammine complex is made by reacting
(1) a cobalt-II salt CoX.sub.2, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(2) an ammonium salt NH.sub.4 X, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(3) ammonium hydroxide (ammonia),
such that the concentration of said cobalt-III hexammine complex is from about 0.1 mole per liter of said aqueous reaction solution up to the saturation limit of said cobalt-III hexammine complex;
and
(b) contacting said substrate with said aqueous reaction 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.

4 more elements

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
(1) preparing cobalt-II hexammine complex by reacting a cobalt-II salt with an ammonium salt and ammonium hydroxide, wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon said aqueous reaction solution to the saturation limit of the cobalt-II salt employed, the concentration of said ammonium salt is from about 0.6 to 12 moles per gallon of said aqueous reaction solution, and the concentration of ammonium hydroxide (ammonia) is from about 1 to 8 moles of NH.sub.3 per gallon of said aqueous reaction solution;
and
(2) oxidizing said cobalt-II hexammine complex to form cobalt-III hexammine complex having a concentration of at least 0.1 mole per gallon of said aqueous reaction solution;
and
(b) contacting said substrate with said aqueous reaction 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.

3 more elements

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 selected from the group consisting of aluminum, aluminum alloy, Cd plating, Zn plating, Zn-Ni plating, and steel, said process comprising the steps of:

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous, alkaline reaction solution comprising a soluble cobalt-III hexammine complex, where said cobalt-III hexammine complex is present in the form of (Co(NH.sub.3).sub.6)X.sub.3, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and where said cobalt-III hexammine complex is made by reacting
(1) a cobalt-II salt CoX.sub.2, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(2) an ammonium salt NH.sub.4 X, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(3) ammonium hydroxide (ammonia),
such that the concentration of said cobalt-III hexammine complex is from about 0.1 mole per liter of said aqueous reaction solution up to the saturation limit of said cobalt-III hexammine complex;
and
(b) contacting said substrate with said aqueous reaction 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.

4 more elements

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 selected from the group consisting of aluminum, aluminum alloy, Cd plating Zn plating, Zn-Ni plating, and steel, said process comprising the steps of:

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by
(1) preparing cobalt-II hexammine complex by reacting a cobalt-II salt with an ammonium salt and ammonium hydroxide (ammonia), wherein the concentration of said cobalt-II salt is from about 0.1 moles per gallon of said aqueous reaction solution to the saturation limit of the cobalt-II salt employed, the concentration of said ammonium salt is from about 0.6 to 12 moles per gallon of said aqueous reaction solution, and the concentration of ammonium hydroxide (ammonia) is from about 1 to 8 moles of NH.sub.3 per gallon of said aqueous reaction solution;
and
(2) oxidizing said cobalt-II hexammine complex to form a soluble cobalt-III hexammine complex having a concentration of at least 0.1 mole per gallon of said aqueous reaction solution;
and
(b) contacting said substrate with said aqueous reaction 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.

3 more elements

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting
(1) a cobalt-II salt CoX.sub.2, where X is selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(2) an ammonium salt NH.sub.4 X, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(3) ammonium hydroxide (ammonia),
such that the concentration of said cobalt-II salt is from about 0.1 mole per liter of said aqueous reaction solution up to the saturation limit of said cobalt-II salt, the concentration of said ammonium salt is from about 0.6 to 12 moles per gallon said aqueous reaction solution, and the concentration of said ammonium hydroxide (ammonia) is from about 1 to 8 moles per gallon of said aqueous reaction solution;
and
(b) contacting said substrate with said aqueous reaction 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.

4 more elements

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

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting
(1) a cobalt-II salt CoX.sub.2, where X is selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(2) an ammonium salt NH.sub.4 X, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(3) ammonium hydroxide (ammonia),
such that the concentration of said cobalt-II salt is from about 0.1 mole per liter of said aqueous reaction solution up to the saturation limit of said cobalt-II salt, the concentration of said ammonium salt is from about 0.6 to 12 moles per gallon of said aqueous reaction solution, and the concentration of said ammonium hydroxide (ammonia) is from about 1 to 8 moles per gallon of said aqueous reaction solution;
and
(b) contacting said substrate with said aqueous reaction 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.

4 more elements

(a) providing an oxide film forming cobalt conversion solution comprising an aqueous reaction solution prepared by reacting
(1) a cobalt-II salt CoX.sub.2, where X is selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(2) an ammonium salt NH.sub.4 X, where X is one or more selected from the group consisting of Cl, Br, NO.sub.3, CN, SCN, 1/3PO.sub.4, 1/2SO.sub.4, C.sub.2 H.sub.3 O.sub.2, or 1/2CO.sub.3, and
(3) ammonium hydroxide (ammonia),
such that the concentration of said cobalt-II salt is from about 0.1 mole per liter of said aqueous reaction solution up to the saturation limit of said cobalt-II salt, the concentration of said ammonium salt is from about 0.6 to 12 moles per gallon of said aqueous reaction solution, and the concentration of said ammonium hydroxide (ammonia) is from about 1 to 8 moles per gallon of said aqueous reaction solution;
and
(b) contacting said substrate with said aqueous reaction 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.

4 more elements

Dependencies are inferred from the claim text.

Non-chromated oxide coating for aluminum substrates

Life of this patent

Non-chromated oxide coating for aluminum substrates

Life of this patent

Abstract

Claims51