GB1365227A - Composition and method for removing copper containing iron oxide scales from ferrous metals - Google Patents

Abstract

1365227 Cleaning ferrous metal HALLIBURTON CO 30 May 1972 25212/72 Heading C7E An aqueous cleaning solution for the removal of iron oxide and copper deposits from ferrous metal comprises an acidic solvent and a copper complexor comprising a mixture of at least one compound (1) and at least one compound (2) where (1) is and (2) is each of said compounds constituting not more than 80 wt. per cent of said mixture R 1 , R 2 , R 3 and R 4 being H, straight or branched C 1 -C 3 alkyl or C 2 -C 3 alkenyl, R 5 being - (CH 2 ) m - where m = 2, 3, or 4, where n = 0, 1, 2, or 3, or and R 6 being H or - CH 2 CH 2 OH. Preferred compounds (1) are thiourea, monomethyl thiourea, 1, 3, dimethyl thiourea, monoethyl thiourea and 1, 3-diethyl thiourea and preferred compounds (2) are ethylene thiourea, N-(2 hydroxyethyl) ethylene thiourea, hexahydropyrimidine - 2 - thione and 4-methyl imidazoline-2-thione, but other compounds are listed. Preferably no compound constitutes less than 5% of the mixture; 2-10 compounds may be present. The complexor is added, e.g. in amount 0À1-5 wt. per cent to an aqueous solution containing e.g. 0À5-50 wt. per cent of a solvent for iron - and copper - containing deposits on ferrous metal, e.g. HF, HCl, H 2 SO 4 , NH 2 SO 3 H, H 3 PO 4 , NaHSO 4 , KHSO 4 , NH 4 HSO 4 , NaHF 2 , monosodium citrate, citric-, aceticgluconic-, hydroxyacetic- or formic acid; the solution may have pH<5 and also contain 0À1-1 vol% corrosion inhibitor and an oxidant for Cu; contact is preferably with agitation, e.g. at 50-175‹F for 2-12 hours.