ORGANIC COMPOSITE COATED STEEL PLATE EXCELLENT IN ELECTRODEPOSITION PAINTING PROPERTIES AND CORROSION RESISTANCE

摘要

PURPOSE:To enhance electrodeposition painting properties and corrosion resistance by dissolving a specific amount of hydrophilic polyamine and/or a polyimine resin in a resin solution for forming a topcoating film. CONSTITUTION:A chromate film being a lower layer and a dry film being an upper layer having a thickness of 0.2-6mum formed from a paint composition wherein three components A, B, C are contained in an org. solvent are provided on the single plated surface or both plated surfaces of a zinc plated steel plate. The component A is 100 pts.wt. of an org. solvent soluble binder resin with a number average MW of 600-100000 formed from a monomer containing 25mol.% or more of an aromatic hydroxy compound and the component B is 10-150 pts.wt. of a hydrophilic polyamine and/or a polyimine resin with a number average MW of 600-100000 formed from a monomer containing 25mol.% or more of an amine compound and the component C is 5-150 pts.wt. of silica particles with an average primary particle size of 1-100nm. By this method, not only excellent corrosion resistance but also excellent electrodeposition painting properties and weldability are imparted and chromium elution quantity can be reduced.