PAINTED STEEL PLATE EXCELLENT IN CORROSION RESISTANCE

摘要

PURPOSE:To obtain a painted steel plate excellent in corrosion resistance, by applying under coat treatment to a plated steel plate by using an aqueous suspension containing a chromic acid mixture before painting. CONSTITUTION:An aqueous suspension containing chromic acid and iron phosphate in an amount of 0.1-20 times chromic acid in a mol ratio is applied to a plated steel plate in an amount of 30-600mg/m<2> as a chromium amount and dried to be cured. In addition, a paint is applied to the treated steel plate, and dried to be cured to obtain a painted steel plate. According to circumstances, dicarboxylic acid or diol is added to the aqueous suspension as a reducing agent in an amount of 0.5 times mol on the basis of chromic acid.