Patent ID: 6461450
Filing Date: 2002-10-08
Classification: C23C

Abstract:
A process for adjusting a coating weight during the phosphating of steel strip zinc-coated on one or both sides which comprises contacting said zinc side of said steel strip for from 2 to 30 seconds with a phosphating solution that comprises:(A) from 1 to 6 g/l of zinc ions; (B) from 10 to 30 g/l of phosphate ions; (C) from 3 to 100 mg/l of Fe(ii) ions, and (D) at least one source of hydroxylamine and all sources of hydroxylamine present have a stoichiometric equivalent hydroxylamine that is from 0.1 g/l to about 3 g/l, said adjusting being accomplished by adding to said phosphating solution from 3 to 20 mg/l of Fe(II) ons in order to reduce the layer weight by 0.1 g/m2 or by removing from said phosphating solution from 3 to 20 mg/l of Fe(II) ions in order to increase the layer weight by 0.1 g/m2, other phosphating variables remaining the same when the Fe(II) ions are added or removed to provide the coating in a weight of 1 to 2 g/m2 and wherein the phosphating solution does not contain accelerators which oxidize Fe(II) and Fe(III).