Selective removal of copper or its oxide from metals - via cleaning soln. contg. poly:amino-carboxylic acid and an oxidant

摘要

The metal surfaces are treated with polyaminocarboxylic acids (PACA) or their derivs., and possibly oxidising agents (a), at 20-120 degrees C. and pH 2-11, in a circulating system with simultaneous and continuous regeneration of the PACA. The pref. PACA is nitrilotriacetic acid (NTA), or its derivs., using 0.01-10 g/l, esp. 0.01-1 g/l, at 60-90 degrees C. and pH 6-9. The soln. of PACA, esp. NTA, is pref. regenerated by removing the cupric ions from the copper complex in the soln. via a synthetic resin ion exchanger at 60-90 degres C. and in the circulating system. Used esp. the cleaning of steel surfaces employed in heat- generating or -distributing systems, where Cu and its oxides are removed from the steel by an economic process.