To provide a galvanized steel sheet in which the individual defects of a manganese based film, a titanium based film and a molybdenum based film are offset with each other, and corrosion resistance after working is remarkably improved.
In this galvanized steel sheet, a chemical conversion film containing soluble compound forming metals such as Mo, V, W, Nb and Ta and complex compounds of Mn and Ti is formed on the surface of a galvanized layer. Mn and Ti as the constituting components of the complex compounds are fed as oxides, fluorides, phosphates, organic acid salts or the like, and the soluble compound forming metals are fed as oxyacid salts. As the organic acid, the one containing a carboxylic group is preferable. The chemical conversion film is formed by coating the galvanized steel sheet with a chemically treating solution containing a manganese compound, a titanium compound, a molybdic compound, phosphoric acid or a phosphate and an organic acid, and whose pH is controlled to pH 1 to 6 and heating and drying the same at 50 to 200°C without performing water washing.
MORIKAWA SHIGEYASU
MATSUNO MASANORI
NAKANO TADASHI
ARIYOSHI YASUMI
TAKETSU HIROBUMI
