process for the production of acid chromium (iii) - containing and objective passivierungsbades for surface of zinc, zinc and cadmium.

摘要

An acidic chromium(III)-containing and fluoride-containing passivating bath for surfaces of zinc, zinc alloys and cadmium is prepared by mixing 20-200 g/l of a soluble chromium(III) compound, 20 to 600 g/l of a soluble nitrate, 5 to 100 g/l of a fluoride and of a sulphate, phosphate, chloride, bromide, fluoride or iodide anion, adding hydrochloric or nitric acid to a pH of 1.8 to 2.2 and heating to above 60 DEG C or adding a catalyst, the amount of nitrate being greater than the chromium(III) concentration. It contains one or more complex(es) of the formula (1): IMAGE (x = 1 to 3, n = valency of A and A = nitrate, sulphate, phosphate, chloride, bromide, fluoride or iodide).