METHOD OF FORMING HEXAVALENT CHROMIUM-FREE CORROSION RESISTANT FILM ON ZINC-NICKEL ALLOY PLATING, AND ACTIVATION LIQUID FOR ZINC-NICKEL ALLOY PLATING USED FOR THE METHOD

摘要

PROBLEM TO BE SOLVED: To provide a method for forming a trivalent chromate film having high corrosion resistance comparable to that of hexavalent chromate on zinc-nickel alloy plating having a nickel content of≤8%. SOLUTION: The method for forming a hexavalent chromium-free corrosion resistant film on a zinc-nickel alloy plating comprises: a step (a) wherein zinc-nickel alloy plating having a nickel eutectoid ratio of≤8% is precipitated over a substrate; a step (b) wherein the precipitated zinc-nickel alloy plating is dipped into an activation liquid containing at least one kind of inorganic mineral acid and having a pH of≤1; and a step (c) wherein the zinc-nickel alloy plating dipped into the activation liquid is treated with a trivalent chromate liquid. COPYRIGHT: (C)2005,JPO&NCIPI