GB986044A - Process and composition for phosphatizing metals - Google Patents

Abstract

A phosphating composition for the surfaces of metals, such as Fe, Al, Zn, Mg, Cd or alloys thereof, comprises 65-98% of a chlorinated hydrocarbon such as C2HCl3, C2Cl4, C2H2Cl4, C2H3Cl3, C2H4Cl2 or CH2Cl2, 0.1-6% of orthophosphoric acid, 1.5-35% of a solvent capable of dissolving the acid in the chlorinated hydrocarbon, such as an aliphatic or alicyclic alcohol containing 1-18 carbon atoms, e.g. n-butanol, and 0.01-6% of an organonitro compound which may be aliphatic, e.g. nitro-methane, -ethane, -urea, -guanidine, and/or aromatic, e.g. (di)nitrobenzene. Compounds substituted with Cl, OH and/or COOH groups may be used, such as 1-chloro-4-nitrobenzene, p-nitrophenol, o-, m- or p-nitrobenzoic acid or picric acid. A comparative example is specified with the organonitro compound replaced by dibutylphthalate. Numerous alcohols are specified together with other solvents such as halogenated alcohols, polyols, alkyl acetates, e.g. ethyl or amyl, amides, e.g. dimethyl formamide/acetamide, dioxane, polyalkylene oxide glycol ethers, e.g. cellosolves or carbitols, ketones, e.g. acetone, and dialkyl sulphoxides, which may be used in place of or with the alcohol solvent. Numerous stabilizers are specified for unstabilized chlorinated hydrocarbons (see Specification 984,612). The comopsition may be initially treated with powdered iron or other metal being treated, e.g. between 0.01% and 0.1% by weight of the composition, prior to contacting the degreased steel or other metal surface with the composition, e.g. by immersion or spraying.