ORGANIC COMPOSITE PLATED STEEL PLATE EXCELLENT IN PRESS FORMABILITY, WELDABILITY, ELECTROCOATING PROPERTY AND CORROSION RESISTANCE

摘要

PURPOSE:To obtain an organic composite plated steel plate having high corrosion resistance, high workability and excellent electrocoating property by a method wherein a hard-to-dissolve chromate film is formed on a plated steel plate and, further, specified coating composition is applied onto said film as a solid film. CONSTITUTION:A hard-to-dissolve chromate film is formed by 10-150mg/m2 on a steel plate plated with zinc-based alloy. Onto said film, coating composition containing 30 wt.% or more of bisphenol type epoxy resin having a mean molecular weight of 300-100000 in coating solids, 1/10-20/10 by weight of hardener consisting of polyisocyanate compound or blocked polyisocyanate compound with respect to epoxy resin solid, 5-50wt.% of fumed silica having mean particle diameter of 0.1-100mum in coating solids and 40wt.% or more of ketone-based organic solvent with respect to the weight of coating and having 10-50wt.% of coating solids, is applied in the form of a thin film of 0.3-5mum as solid film. Thus, an organic composite plated steel plate excellent in press formability, weldability, electrocoating property and corrosion resistance is obtained.