PURPOSE: To remove rust on the surface of steel and a heat scale at the weld zone and to form an iron phosphate film with one liq. in one stage by using an undercoat processing agent obtained by mixing hydrogen peroxide and a fluoric surfactant into an aq. phosphoric acid soln.
CONSTITUTION: About 0.2-0.6wt./vol.% hydrogen peroxide and about 0.005-0.03 wt./vol.% fluoric surfactant are mixed into an aq. 10-20wt./vol.% phosphoric acid to prepare an undercoat processing agent of the surface of steel. The mill scale, red rust and the heat scale on the weld zone on the surface of various products, large-sized structure, etc., consisting of a steel material to be coated are removed with this processing agent. Further, since a rust-resistant iron phosphate film is formed on the derusted steel surface, the adhesion of coating material to the substrate is improved.
SHIBATA AKIO
FURUSAWA TAKETOSHI
