| 摘要 |
PURPOSE:To obtain a surface preparation treated and multilayer corrosion protection coated steel material excellent in adhesion and cathodic peeling resistance by forming a chromating undercoat layer of specific composition on the surface of a steel material and then laminating plural specific organic films on it. CONSTITUTION:A chromating undercoat layer 2, prepared by using a chromating agent where phosphoric acid and chromic anhydride are mixed so that the proportion of phosphoric acid to the total chromium of chromic anhydride becomes 0.2-3.0 by weight ratio and fine SiO2 grains, partially reduced by an organic reducing agent such as methyl alcohol and synthesized by a dry method and consisting of 20-70wt.% of SiO2, grains of 5-20nm primary grain size and 30-80% of SiO2 grains of SiO2 grains of 20-120nm primary grain size in the form of mixture, are added by 0.5-4.0 by weight ratio based on the total chromium of chromic anhydride, is formed on the surface of a steel material 1. Subsequently, an epoxy primer layer 3, a modified polyolefin adhesive layer 4, and a polyolefin coating layer or cross-linked polyolefin coating multilayer corrosion protection layer 5 are successively formed on the above. |
