Treating phosphated metal surfaces - with soln. contg. (1)-phenyl-vinyl-phosphonic acid-(1) or (co)polymer, buffered with fumaric acid or succinic acid

摘要

Phosphated metal surfaces are post-treated with a soln. contg. 1-phenyl-vinyl-phosphonic acid-1 (I), its polymer and/or copolymer with an alkenically unsatd. monomer. The pH of the bath is kept at 4-5.5 using fumaric acid or succinic acid as buffer. Fumaric acid and succinic acid are not complexing agents for the Fe in the phosphated surface, and have stronger buffering action than phosphoric acid. The treatment gives good protection against rusting. The soln. contains 0.01-1 (0.05-0.2)g acid/litre. Pref., the initial pH is brought to 4 by addn. of an amine, esp. triethanolamine.