| 摘要 |
A surface treated steel sheet having double layers consisting of a lower layer of metallic chromium and an upper layer of hydrated chromium oxide are formed on a low tin plated steel sheet in which 30 to 80% of the surface of the steel sheet is covered with plated tin. Also, the ratio of the area of tin, which actually combined with steel sheet, to the projected area of plated tin to the steel sheet is 20 to 90% and the size of the exposed steel surface units, after tinplating, is 0.5 to 20 mu m in diameter when expressing the irregularly exposed areas as circles, and a method for production of this surface treated steel sheet which comprises; (a) electroplating with a small amount of tin under restricted conditions in order to obtain the low tin plated steel sheet described above, (b) after reflowing or without reflowing of the plated tin, formation of said double layer or formation of the metallic chromium layer followed by formation of hydrated chromium oxide under restricted conditions. This surface treated steel sheet is suitable for producing a welded can body without removing the plated layer at high speed, since it is excellent in weldability, lacquer adhesion and corrosion resistance after lacquering. |
