High speed spray or dip phosphating of steel strip

摘要

High speed spray or dip phosphating of optionally galvanized steel strip is carried out using a nitrate-free acid phosphating solution which contains 1-4 g/l zinc ions, 1.2-4 g/l manganese ions, 1-4 g/l magnesium ions, 10-30 g/l phosphate ions and 0.1-3 g/l free or combined hydroxylamine and which has free and total acid contents of 0.4-4 points and 15-45 points respectively.