SURFACE TREATMENT LIQUID FOR GALVANIZED STEEL SHEET, TREATED STEEL SHEET, AND TREATMENT METHOD

摘要

PROBLEM TO BE SOLVED: To impart corrosion resistance excellent even after alkali degreasing to a galvanized steel sheet by surface treatment capable of baking at a low temperature. SOLUTION: The surface treatment liquid contains: a water soluble polyvalent metal phosphate compound selected from aluminum primary phosphate and magnesium primary phosphate; a chelating agent selected from a phosphonic acid based chelating agent and an oxycarboxylic acid based chelating agent; and a corrosion inhibitor selected from a vanadic acid compound and a polyamine compound shown by formula (1). The surface treatment liquid is applied to a galvanized steel sheet, and then is baked at 50 to 200°C to form a coating film. Therein the formula (1), R1and R2are each a hydrogen atom or a methyl group; R3is sulfur dioxide, acrylamide, a diallylamine hydrochloride or a derivative thereof; and n is an integer of≥2. COPYRIGHT: (C)2005,JPO&NCIPI