HIGHLY CORROSION-RESISTANT ORGANIC COMPOSITE COVERED STEEL PLATE

PURPOSE:To obtain highly corrosion-resistant organic composite covered steel plate, the corrosion resistance and electrocoating properties of which are highly balanced with each other, by a method wherein chromate film layer, organic resin covering layer and ultra-thin metal. covering layer are laminated onto the surface of plated steel plate in the order named. CONSTITUTION:Matrix plated steel plate is steel plate plated with pure zinc or zinc-based alloy excellent in corrosion resistance. Any plating method among electroplating, melt plating, alloyed melt galvanizing, metallizing and the like can be employed as the method for plating the steel plate. In order to form the first layer chromate film, application type chromate film, which is especially excellent in corrosion resistance, is preferably used and the preferable coating built up is 10-600mg/m by the weight of metal chromium. As the kind of organic resin film to be formed on the chromate film, there is no special limitation and epoxy-based resin with the covering film thickness of 0.1-10mum is especially preferable. As the kind of the ultra-thin metal covering formed as the third layer, metals, which are excellent in resistance to salt water, such as Ni, Cr, Co, Mn, Cu or the like or their alloys are preferably employed. The coating built up of the covering layer is set to be 0.1-10g/m . As a result, red rust is prevented from developing and highly corrosion-resistant organic composite covered steel plate is obtained.