CLEANING METAL SURFACES

1300442 Cleaning compositions DOW CHEMICAL CO 25 Feb 1970 9138/70 Heading C7E A metal cleaning solution comprises 0À001 to 0À1 wt per cent of a water soluble sulphide, the sulphide (1) having a majority of molecules capable of releasing sulphide ions, (2) having no cations which will plate out on a clean ferrous metal surface (3) being safe to handle and (4) having a water solubility of at least 0À1% by wt in the cleaning solution; 0À5-40 wt per cent of an alkylene amine carboxylic acid of formula wherein n = 1-4, m = 0-4 and wherein up to two of the carboxymethyl groups may be replaced with a #-hydroxyethyl group and one or more of the carboxymethyl groups may be replaced by carboxyethyl groups; ammonia or alkili; and water. Typical sulphides are Na 2 S, K 2 S, (NH 4 ) 2 S, thioglycolic acid, dithioethanol or mercapto benzothiazole; typical acids are EDTA, N-hydroxyethyl ethylenediaminetriacetic acid, nitrilotriacetic acid, N-2-hydroxyethyl-iminodiacetic acid or diethyleneentriomine acetic-acid. The solution may have pH 7-11, may contain an inhibitor, and is used at 70-190‹C. to clean steel surfaces, particularly those contaminated with Cu.