摘要:
The process for removing a soap-contaminated conversion layer remaining on a metal workpiece after cold-forming with an aqueous acidic cleaning composition containing water, a surfactant such as an alkyl amine ethoxylate and nitric acid, phosphoric acid and/or amidosulphonic acid includes immersing the contaminated metal workpiece in the aqueous acidic cleaning composition at a temperature above 60.degree. C. until it has a clean bright surface and a fatty acid formed by reaction of the soap in the conversion layer is dispersed in the cleaning composition and then subsequently separating the metal workpiece from the cleaning solution and, after the separating, cooling the recovered aqueous acidic cleaning composition to a temperature below 55.degree. C. until a fatty acid layer including the fatty acid is separated from the aqueous acidic cleaning composition. The fatty acid layer is removed from the aqueous acidic cleaning composition to form a reusable aqueous acidic cleaning composition and then other metal workpieces are cleaned with the reusable aqueous acidic cleaning composition.