PRODUCTION OF ORGANIC COMPOSITE MATERIAL COATED STEEL SHEET EXCELLENT IN BOTH IMAGE CLARITY AFTER ELECTRODEPOSITION COATING AND COATING MATERIAL ADHESION

摘要

PURPOSE: To stably produce the coated steel sheet which can meet the requirements with respect to both electrodeposition coating suitability, in particular image clarity after electrodeposition coating, and coating material adhesion and also has good rust preventing properties, low temp. chipping resistance, etc. ;CONSTITUTION: This production method comprises forming a chromate layer having a 5 to 500mg/m² coating weight in terms of Cr on the surface of a galvanized steel sheet, then, coating the surface thereof with a 0.1 to 3g/m² in terms of dry weight of an organic composite coating material composition and thereafter, drying the resulting steel sheet. This organic composite coating material composition contains a silica sol that is dispersed in an organic solvent and has 0.1 to 2μm average aggregate particle size and a 40 to 800m²/g aggregate specific surface area, which aggregate is formed through the aggregation of primary particles having 5 to 30nm average particle size, or chainlike fumed silica that is formed through joining the primary particles to each other and has ≥0.1μm average length, and a resin composition having an amine value of 40 to 150 based on the amount of the resin solid.;COPYRIGHT: (C)1996,JPO