GB860958A - Improvements in and relating to the prevention of corrosion - Google Patents

Abstract

860,958. Preventing corrosion. IMPERIAL CHEMICAL INDUSTRIES Ltd. April 17, 1959 [March 27, 1958], No. 9931/58. Class 123(1) Corrosion of water cooling systems and the tanks of tanker vessels carrying sea water ballast is inhibited by adding to the water minor amounts of a composition consisting of an alkali salt of a carboxylic acid containing an aromatic or a cyclic aliphatic group, an alkali metal nitrite and an alkali metal borate or phosphate to act as a buffer agent. The carboxylate is preferably a sodium salt of an acid from one of the following groups:-unsubstituted aromatic acids, e.g. benzoic acid; acids as in the first group containing an alkyl substituent, e.g. 4-methyl benzoic acid; acids as in the first group containing an alkoxy substituent, e.g. 4-methoxy benzoic acid; unsubstituted acids produced by the partial or complete hydrogenation of acids as in the first group, e.g. hexahydrobenzoic acid; acids as in the last group containing an alkyl or alkoxy substituent, e.g. 4-methyl cyclohexane carboxylic acid; acids in which an aromatic group is separated from a carboxylic acid group by an aliphatic grouping, e.g. phenyl acetic acid; acids as in the last group containing an alkyl or alkoxy group in the 4-position to the side chain; acids as in the last two groups in which the aromatic nucleus has undergone partial or complete hydrogenation, e.g. hexahydrophenyl acetic acid; acids having the structure Ar-OCH 2 COOH where Ar is an aromatic radical, e.g. 4-nonyl phenoxy acetic acid; the cyclohexyl ether of glycollic acid or substituted derivatives thereof containing alkyl or alkoxy groups, e.g. cyclohexyl glycollic acid and finally acids as in the last group except that hydrogenated aromatic radicals other than cyclohexyl are employed, e.g. decahydro-2-naphthoxy acetic acid. When the inhibitor is used in cooling systems at elevated temperatures, e.g. 80-90‹ C., of the metal surface the carboxylate is present in the proportion of from 1% by weight when a salt of an acid of low molecular weight, e.g. sodium benzoate, is used to 0À02% when a high molecular weight salt such as sodium para-nonyl phenoxyacetate is used, sodium nitrite and sodium borate each being present in the proportions of 0À1 % by weight. When employed under cold conditions, e.g. in sea water ballast tanks, the proportion of carboxylate is increased up to 5 % and the nitrite and buffer agent to 0À5%. Small amounts of calcium and magnesium salts may be admixed with the inhibitor, where these salts are not present in the water, to increase the efficiency thereof.