Method for electroplating

Claim 2

IN THE METHOD OF ELECTROPLATING DIE CASTINGS COMPOSED OF ZINC OR ZINC ALLOYED WITH AT LEAST ONE OF MAGNESIUM AND ALUMINUM WITH A LESS ELECTRONEGATIVE METAL OR ALLOY IN A CYANIDEFREE ELECTROLYLE COMPRISING AN AQUEOUS SOLUTION OF A COMPLEX OF SAID LESS ELECTRONEGATIVE METAL OR ALLOY AND AN ORGANOPHOSPHORUS COMPOUND, THE IMPROVEMENT WHICH COMPRISES CONTACTING THE CATHODE WITH AN AQUEOUS SOLUTION CONSISTING ESSENTIALLY OF FROM ABOUT 0.1 PERCENT UP TO THE LIMIT OF SOLUBILITY OF AN ORGANOPHOSPHORUS CHELATING AGENT FOR SAID CATHODE PRIOR TO IMMERSING THE CATHODE IN SAID ELECTROLYTE.

Claim 3

A method of claim 1 wherein the less electronegative metal is copper, nickel, tin, silver or gold.

Claim 4

A metHod of claim 1 wherein the organophosphorus compound of said electrolyte and said chelating agent are the same organophosphorus compound.

Claim 5

A method of claim 1 wherein said organophosphorus compound and said chelating agent are selected from the group consisting of amino C1-12 alkylidene phosphonic acid, polyamino C2-6 alkylene poly(C1-12 alkylidene phosphonic acid) and C1-5 alkylidene diphosphonic acid.

Claim 6

A method of claim 1 wherein said organophosphorus compound and said chelating agent are selected from the group consisting of 1-hydroxyalkylidene-1,1-diphosphonic acid and ethylene diamine tetra(methylene phosphonic acid).

Claim 7

In a method of electroplating die castings of zinc and alloys of zinc containing at least one of magnesium and aluminum with a more noble metal selected from the group consisting of copper and nickel in an electrolyte comprising an aqueous solution of said copper or nickel and an organophosphorus compound, the improvement which comprises contacting the zinc or zinc alloy prior to immersion in the electrolyte with an aqueous solution consisting essentially of from about 0.1 percent up to the limit of solubility of an organophosphorus chelating agent which is capable of forming a zinc ligand.

Claim 8

In a method of electroplating die castings of zinc and alloys of zinc containing at least one of magnesium and aluminum with a more noble metal selected from the group consisting of copper and nickel in an electrolyte comprising an aqueous solution of said copper or nickel and an organophosphorus compound, the improvement which comprises contacting the zinc or zinc alloy prior to immersion in the electrolyte with an aqueous solution consisting essentially of from about 0.1 percent up to the limit of solubility of an organophosphorus chelating agent which is capable of forming a zinc ligand.

Claim 9

A method of claim 6 wherein said organophosphorus compound and said chelating agent are selected from the group consisting of amino C1-12 alkylidene phosphonic acid, polyamino C2-6 alkylene poly(C1-12 alkylidene phosphonic acid) and C1-5 alkylidene phosphonic acid.

Claim 10

A method of claim 6 wherein said organophosphorus compound and said chelating agent are selected from the group consisting of 1-hydroxyalkylidene-1,1-diphosphonic acid and ethylene diamine tetra(methylene phosphonic acid).

Claim 11

A method of claim 6 wherein the pH of said aqueous solution of said organophosphorus chelating agent is about 1.5 to 2.0.

Claim 12

A method of claim 6 wherein the concentration of said organophosphorus chelating agent in said aqueous solution is from about 0.5 to 2.0 percent.

Claim 13

A method of claim 6 wherein the organophosphorus compound of said electrolyte and said chelating agent are the same organophosphorus compound.