IMPROVED BLACK RUST PREVENTION-TREATED METAL, COMPOSITION FOR FORMING BLACK RUST PREVENTIVE FILM, AND METHOD OF FORMING BLACK RUST PREVENTIVE FILM

摘要

PROBLEM TO BE SOLVED: To provide a black rust prevention-treated metal in which a black rust preventive film having excellent rust preventability, maintaining the rust preventability even if flaws are generated thereon, and free from discoloration and decolorization is formed on the surface of a metallic substrate without using harmful hexavalent chromium, to provide a composition for forming a black rust preventive film, and to provide a method of forming a black rust preventive film.;SOLUTION: The black rust prevention-treated metal 1 is provided with: a black metal sulfide-containing first black rust preventive film 4 formed so as to be closely stuck to the surface of a metallic substrate 2, comprising V as an essential component and further comprising one or more kinds selected from Co, Ni, Ti and W; a second rust preventive film 5 formed so as to overlap with at least a part of the first black rust preventive film 4 and mainly comprising metallic ions having an ionization tendency equal to or above that of the metal(s) for blackening composing the first black rest preventive film 4 and/or a metallic compound; and a third rust preventive film 6 formed so as to overlap with at least a part of the second rust preventive film 5 and essentially consisting of tannic acid.;COPYRIGHT: (C)2007,JPO&INPIT