Abstract: Corrosion inhibiting compositions for addition to aqueous acid metal cleaning compositions for use in the cleaning of surfaces of metal parts which are contaminated with water insoluble, acid soluble deposits, wherein the corrosion inhibiting composition contains a partially hydrolyzed protein which is either a partially hydrolyzed gelatin, a partially hydrolyzed casein or a mixture thereof wherein the partially hydrolyzed protein has a total nitrogen content of from about 10 to about 20% by weight and a free amino group nitrogen content of from about 4 to about 30% based on the total nitrogen content. The invention also relates to aqueous acid solutions containing the corrosion inhibitor of the invention and to processes for treating contaminated metal parts with such acid compositions.

Abstract: Acid cleaning compositions containing an inhibitor for cleaning metal surfaces, processes for cleaning metal surfaces therewith, and concentrates useful in forming the acid cleaning compositions. The present acid cleaning compositions contain an acid, a Mannich base, a thiourea, an alkyl trimethyl ammonium halide and/or an alkyl (C.sub.8 -C.sub.9) phenoxypolyethoxy ethanol, and a nonionic surfactant which is a condensate of poly(oxyethylene) and poly(oxypropylene) groups.