RUSTPROOF, LUBRICATED STEEL PLATE SUBJECTED TO CHEMICAL CONVERSION TREATMENT

PURPOSE:To improve the stability of a coating film in a high temperature region, lubricity, rustproofness, water solubility, etc., by applying a specified aqueous treating solution to a surface of a steel plate and drying it to form a coating film through chemical conversion with iron phosphate and a water-soluble solid lubricating film on the surface. CONSTITUTION:An aqueous solution (a) is prepared by mixing 100 pts.wt. polyethylene oxide having a molecular weight of 2,000 to 40,000, 0.5-100 pts.wt. water-soluble rustproofing agent, 0.5-100 pts.wt. (solid) colloid (sol) of at least one of SiO2, Cr2O3, Fe2O3, MgO, ZrO2, SnO2, Al2O3, CaCO3, etc., and the balance of water. This solution is mixed with an iron phosphate solution, used for chemical conversion treatment, in an amount of 5.0-13.0g/l in terms of phosphoric acid to give an aqueous treating solution. This solution is applied to a surface of a steel plate and dried to form thereon a film having a coating weight of 0.1-1g/m for one surface through chemical conversion with iron phosphate and on this film a water-soluble solid lubricating film having a coating weight of 0.5-5.0g/m for one surface.