Cleaning metal surfaces - before phosphating, in cascade system giving uniform phosphating and reducing water requirements

摘要

In cleaning metal surfaces, esp. steel or zinc- treated steel surfaces, by spraying, the metal articles pass in sequence through =1 spray zone using alkaline aq. cleaning solns. and then through =1 spray-rinsing zone using wetting agents, before entering a phosphating zone; clean water and wetting agent are added, pref. continuously to the last rinsing zone before the phosphating; rinsing water contg. excess, already used, wetting agent from this bath, passes as a cascade into the previous baths, the inorganic system of the alkaline cleanser is metered into =1 of these baths, and the exhausted cleanser is removed from the cleansing baths in the amt. by which rinsing water is added. The metal surface is completely wetted with rinsing water when it enters the phosphating zone. A uniform phosphate coating is produced and accumulation of impurities in the baths is avoided. The process can be operated automatically, with little personnel.