| 摘要 |
PURPOSE:To obtain a black colored steel sheet having little luster without requiring coating by pretreating a steel sheet plated with a Zn-Al alloy contg. a specified amount of Al with the soln. of a special acid or alkali and by subjecting the pretreated steel sheet to chemical conversion treatment. CONSTITUTION:The steel sheet plated with a Zn-Al alloy contg. 2.5-10wt% Al- is pretreated by immersion in the aqueous soln. of an acid such as HCl, an alkali such as NaOH or FeCl3 or a mixed soln. contg. an acid and FeCl3. The pretreated steel sheet is washed and immersed at once in a zinc phosphate soln. for chemical conversion treatment. By this method the black colored steel sheet having little luster, a pure black color, superior corrosion resistance and workability is obtd. |
