GB865914A - Composition and process for the cleaning of metal parts - Google Patents

Abstract

A cleaning solution for removal of leaded deposits, carbon and heat scale from engine component parts is made by dissolving in water a composition comprising, by weight, 4-40% alkali metal hydroxide or peroxide (calculated as alkali metal oxide), 1-45% of a lead complexing agent selected from the soluble alkali metal salts of an aliphatic hydroxy acid and of a fatty acid of less than 4 carbon atoms, and 5-25% of a compatible alkanolamine or its equivalent alcoholate and/or 3-20% of a phenol or alkali metal phenate. The preferred solution comprises 30-65% water, 10-25% alkali metal hydroxide or peroxide, 1-45% lead complexing agent, and 10-25% of a mixture of a polyalkanolmonoamine having a boiling point above 400 DEG F and an alkali-soluble and alkali-stable polyalkanolpolyamine, said polyalkanolmonoamine being dispersible and stable in alkaline solution at 200-300 DEG F (the temperature at which the solutions are preferably used), and said polyalkanolpolyamine being present in an amount of 0.2-5% by weight of the solution. The solution may also contain (1) a polyol in place of part of the alkanolamine(s), suitable polyols being ethylene-, diethylene-, triethylene- and dipropylene-glycol, glycerol and sorbitol, and (2) a wetting-agent. Specified alkali metal hydroxides are sodium and potassium hydroxide. Specified lead complexing agents are the potassium and sodium salts of lactic, citric, tartaric, gluconic, glyceric, malic, glycollic, saccharic, acetic and propionic acids. Specified polyalkanolmonoamines are di- and tri-ethanolamine, N-methyl- and N-ethyldiethanolamine, di- and tri-isopropanolamine, N, N-dihydroxyethyl glycine, and glycol, polyglycol and polyetherglycol derivatives of triethanolamine. Specified polyalkanolpolyamines are N, N, N1, N1 tetrakis (2-hydoxy-ethyl or -propyl) ethylenediamine, N, N1 dihydroxyethyl ethylenediamine, tetraethanol propylenediamine, pentaethanol diethylenetriamine, hexaethanol triethylenetetramine, and di N-hydroxyethyl ethylenediamine diacetic acid. Suitable phenols are the mono-, di-, and tri-hydric phenols and their homologues. Components which have been treated in the above solutions may be treated, so as to remove any remaining scale, in an aqueous solution containing 10-20% sodium or potassium hydroxide, 3-12% potassium permanganate and, optionally, 5-10% sodium or potassium carbonate. This treatment may be followed, if desired, by brightening in nitric acid or re-treatment in the solutions of the invention. The solutions are stated to be particularly applicable to the cleaning of aircraft engine components made, for example, of chromium and chromium-nickel stainless steels, nickel-base and cobalt-base alloys, iron-chromium-nickel alloys and cobalt-nickel-chromium alloys.