To narrow a color tone for coloring a hot dip galvanizing film down to a blackish dark gray type color tone easy of quality control, to improve the physical properties of a colored film, and to provide a process of coloring a galvanizing film, hardly causing cracking and providing excellent wear resistance as well as atmospheric corrosion resistance under severe conditions.
The process for coloring a galvanizing film is constituted of the following stages: chemical conversion treatment where a galvanized steel material is immersed under the chemical comversion treatment conditions of 30-70°C treatment solution temp. and 2-15 min treatment time by using a chemical conversion treatment solution consisting of (10 to 80) g/l potassium permanganate, (20 to 200) g/l trisodium phosphate, and (10 to 100) g/l sodium hydroxide; after treatment I where the galvanized steel material is immersed under the treatment conditions of 30-70°C treatment solution temp. and 1-10 min treatment time by using a treatment solution composed of (1 to 20) g/l chromic anhydride and regulated to pH 1.0-4.0; and after treatment II where the galvanized steel material is immersed for 30 sec to 2 min in a treatment solution containing 2-10% (resin content) water-soluble resin and regulated to pH 6-10 and 40-80°C.
TAKANO YOSHIHIKO
NAKADA TETSUYA
TAKADA KOJI
MORITA YASUHIRO
KITANO YUJI
