CHROMIUM-FREE RUST INHIBITIVE TREATMENT METHOD FOR METAL PRODUCT HAVING ZINC SURFACE AND METAL PRODUCT TREATED THEREBY

摘要

PROBLEM TO BE SOLVED: To provide a chromium-free surface treatment method which imparts practical rust inhibitive performance to a metal product having a zinc surface to which it was difficult to impart rust inhibitive performance of practical level when a chromium-free surface treatment agent for forming a silica-based film is applied. SOLUTION: A conversion-coated film of zinc phosphate etc. is formed on the zinc surface of the metal product as pretreatment, and the silica-based film is formed by applying a chromium-free surface treatment agent which uses alcohol or mixture of water and alcohol as a solvent to the conversion-coated film. As a result, when an aqueous surface treatment agent containing alcohol is applied, it is possible to suppress the formation of white rusting for 72 hours or longer in the salt spray test. COPYRIGHT: (C)2006,JPO&NCIPI