Reinigungsloesungen und Verfahren zum Reinigen von Metallen

1,201,511. Cleaning metals. DOW CHEMICAL CO. Sept.14, 1967 [Sept.15, 1966], No.41894/67. Heading C7E. Corrosion of metal surfaces while these are being cleaned with alkaline or neutral aqueous solutions with pHs of 7 to 10 of poly-carboxylic acid ammonium or amine complexing or chelating agents is prevented by including in the solution as an inhibitor at least one thioethylamine of formula wherein A is hydrogen or a 1 to 5 carbon alkyl group or a radical of Formula wherein R is an alkyl group, X is 1 or 2, each RÀ may be hydrogen or a 1 to 5 carbon alkyl group and m is 1 to 8, n is 1 to 8, or a hydrosulphide salt thereof or a thioethylamine of formula wherein each R is as above defined and 0 is 1 to 3. Preferably the additive is bis-(2-aminoethyl) sulphide. The solutions contain 0À5 to 40% by weight of the complexing agent and 0À01 to 0À5% by weight of the additive, and may contain 0À01 to 0À20% by weight of an amine-ketone-aldehyde-fatty acid adduct, while sodium nitrite or potassium chromate or air may be introduced during the later stages of cleaning to oxidize any copper present, preferably when the temperature of the cleaning solution has fallen to below 85‹ C. Sulphur-containing amine compounds suitable for use as inhibitors include polyalkyleneamine sulphides and mercaptans, hydroxyalkyl polyalkyleneamine sulphides and polyalkylenepolyamine sulphides, disulphides and mercaptans. Specifically suitable compounds are: bis-(2-aminoethyl) sulphide; bis (2-aminoethyl) disulphide 3-aza-5- thiaoctane, 1, 8-diamine; beta-mercaptoethylamine; thiazolidine; 2-(aminoethylthio) ethanol; thiazole and 2, 2-dimethyl thiazole. Suitable chelating or complexing agents include the alkylene polyamine polyacetic acids EDTA, N-hydroxyethyl ethylenediamine triacetic acid, ethylenediaminetetrapropionic acid, nitriloacetic acid, N-2- hydroxyethyliminodiacetic acid tetramethylene - diamine-N, N, N , N -tetracetic acid, (alphahydroxy ethylimino) diacetic acid, and diethylene triamine pentaacetic acid and N, N-di(#-hydroxyethyl) glycine, and citric acid and tartaric acid. The solutions are normally made alkaline with ammonia or with ethanolamine, ethylamine, ethylenediamine, diethylenetriamine, pentaethylenehexamine, dimethylamine, trimethylamine, ethyleneamine or other amine.