CHROMIUM-FREE SURFACE TREATMENT METHOD FOR IMPARTING CORROSION RESISTANCE TO SURFACE OF STEEL OR GALVANIZED STEEL, AND SURFACE TREATMENT SOLUTION THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a chromium-free surface treatment technique for imparting corrosion resistance to the surface of steel or galvanized steel having a uniform and satisfactory appearance and excellent corrosion resistance without using chromium harmful for the living body and environment.;SOLUTION: A film of a sol solution containing alkoxide, acetylacetonate, carboxylate or nitrate of at least one metallic element selected from Zr, Ti, Ta and Nb is formed on the surface of steel or galvanized steel by immersion or coating, and the film is subjected to hydrolysis and polycondensation reaction to convert the sol into a gel, and the film of the gel is heated at 250 to 350°C in an oxygen atmosphere, so that a protective film with a thickness of 0.1 to 3 μm consisting of oxide of at least one metal selected from Zr, Ti, Ta and Nb is formed.;COPYRIGHT: (C)2003,JPO