| 摘要 |
PURPOSE:To provide a weldable painted steel plate which is improved in corrosion resistance without spoiling workability by forming an under-coating layer and a top-coating layer having respectively specific compsn. at specific thicknesses successively on the surface of a steel plate having specific surface roughness. CONSTITUTION:A stable aq. soln. for coating metallic surfaces contg. 10pts.wt. chromium trioxide wherein 40-50% is reduced to a trivalent state, 3-4pts.wt. phosphoric acid (100% H3PO4), 4-5pts.wt. polyacrylic acid, 17-20pts.wt. solid matter of an acrylic polymer emulsion, and 200-400pts.wt. water for preparing these components into an aq. soln. is coated on the surface of a steel plate having 4-20mu average surface roughness and is dried, whereby an under-coating layer is formed so as to contain 10-50mg/m<2> total amt. of chromium. A top- coating layer consisting of 80.0-91.0pts.wt. metallic zinc powder, 0.2-5.0pts.wt. rust preventive pigment, and 4.0-19.8pts.wt. a synthetic resin is formed further thereon to 10-50mu thickness. |
