Process and aqueous solution for phosphatising metallic surfaces

摘要

An aqueous, phosphate-containing solution is disclosed for generating phosphate layers on metallic surfaces made of iron, steel, zinc, zinc alloys, aluminium or aluminium alloys. The solution contains 0.3 to 5 g Zn2+/l and 0.1 to 3 g nitroguanidine/l, the S-value being comprised between 0.03 and 0.3 and the weight ratio Zn : P2O5 being from 1 : 5 to 1 : 30. Also disclosed is a phosphatising process in which the metallic surfaces are cleaned, then treated with the aqueous phosphatising solution for 5 seconds to 10 minutes at a temperature from 15 to 70 °C and finally rinsed with water.