ORGANIC COMPOSITE COATED STEEL SHEET EXCELLENT IN CORROSION RESISTANCE AND ELECTRODEPOSITION COATING SUITABILITY

摘要

PURPOSE: To develop an organic composite coated steel sheet excellent in corrosion resistance and electrodeposition coating suitability by forming a chromate film and an organic resin film on the surface of a galvanized steel sheet having specified roughness. CONSTITUTION: On one side of a galvanized steel sheet or a galvannealed steel sheet in which the center line average roughness Ra and ten point average roughness Rz on the surface satisfies the relationship of Ra<=0.13×Rz and having surface roughness in which the surface roughness parameter PPI (the number of crests per inch in the case the threshold value is regulated to >=30% of Rmax) is regulated to >=30, a chromate film having 0.1μg/5mm<2> Cr coating weight is formed as a primary layer, and on the surface, an organic resin film of glycydylether series epoxy resin or the like is furthermore formed at >=0.1μm thickness as a secondary layer. The organic composite coated steel sheet excellent in corrosion resistance and electrodeposition coating suitability and suitable as automobile interior and exterior materials can be obtd.