| 摘要 |
PURPOSE:To improve the adhesive property of coated film during coating of steel sheet, by treating steel sheet plated with Zn alloy contg. Al with alkaline liquid contg. nitrate, gluconate, hexahydroxylheptanate of specified metal, then treating with liquid contg. silicic acid and chromic acid. CONSTITUTION:Steel sheet plated with Zn alloy contg. 2-10wt% Al is treated with aqueous soln. having the following compsn. Namely, plates steel sheet is treated by spraying, etc. 50-70 deg.C aqueous soln. contg. 1 or >=2 kinds among nitrates of Ni, Co, Fe and gluconate, hexahydroxylheptanate, and whose pH value is adjusted to >=12 by NaOH, KOH. Next, said sheet is treated with liquid contg. silicic acid, chromic acid to form chemically conversion treated film having 1/2-1/40 weight ratio of Fe to Co or Fe to Ni, and the chemically conversion treated film superior in coating property, coated film adhesive property is formed on steel sheet plated with Zn contg. Al. |
