Process of phosphating before electroimmersion painting

摘要

Disclosed is a composition and a process of using the composition for phosphating a workpiece made of steel or partly galvanized steel in preparation for electro-immersion painting. The cleaned and rinsed workpiece is first activated with a weakly alkaline aqueous solution which contains titanium phosphate and is subsequently dipped into an acid aqueous phosphating solution at a temperature of from 40° to 60. degree. C. which containsPP1.8 to 5 g/l Zn, P P0.1 to 7 g/l Fe(II),PP8 to 25 g/l P. sub.2 O.sub.5, PP5 to 30 g/l NO.sub.3PP and in which the controlled ratio of free acid to total acid is between 0. 04 and 0.07. PPThe phosphating solution preferably contains 3 g/l zinc and 0.5 to 5 g/l iron(II) and additionally contains up to 3 g/l manganese. PPOther suitable components of the phosphating solution are Co, Ni, hydroxylamine, fluorides, tartaric acid, citric acid, and m- nitrobenzene sulfonate.