Patent GB-610724-A (GB)
Title: Improvements in or relating to a method and composition for degreasing and forming an oxide film on metals
IPC: C23C22/67
Filed: 1945-11-30
Abstract: The surfaces of metals are simultaneously degreased and provided with a protective oxide film by treatment with an aqueous solution of a composition comprising an oxidizing component, e.g. sodium chromate, and a degreasant component comprising a detergent and an organic solvent containing at least one hydroxyl group, at least a proportion of the detergent being a water-soluble salt of a sulphonated phenol or a water soluble phenate.  An alkaline component such as sodium carbonate may also be present and the water-soluble salt of a sulphonated phenol may be the sodium salt of a sulphonated commercial cresylic acid.  The water-soluble phenate may be a sodium phenate derived from commercial cresylic acid and the organic solvent may be diethylene glycol or mono or dimethyl cyclohexanol.  The non-phenolic component of the detergent may be an alkyl aryl sulphonate or a surface active sodium salt of an alkyl ester of sulphuric acid.  In an example, 2.5 per cent by weight of a degreasant comprising 50 lbs. of the sodium salt of sulphonated commercial cresylic acid, 30 lbs. of diethylene glycol and 20 lbs. of water, or 0.75 per cent by weight of a degreasant comprising 50 lbs. of "Teepol," 75 lbs. of the sodium salt of sulphonated commercial cresylic acid, 12 lbs. of dimethyl cyclohexanol and 30 lbs. of water is added to an oxidizing bath consisting of 1 1/2 per cent by weight anhydrous sodium chromate, 5 per cent anhydrous sodium carbonate and 93 1/2 per cent water. Heavily greased aluminium sheets are said to be satisfactorily treated by immersion in the bath for 7 minutes at 95 DEG  C., particularly when the pH value of the bath is 10.5 to 11.  The presence of water-soluble salts of sulphonated phenols in the compositions is especially suitable where pH control is desired. Reference is made in the first Provisional Specification to the use of sulphated long chain fatty alcohols as detergents.ALSO:Metals are simultaneously coated with an oxide film and degreased by treatment with an aqueous solution of an oxidizing agent, e.g. sodium chromate, and a degreasant comprising a detergent and an organic solvent containing at least one hydroxyl group, at least a proportion of the detergent being a water-soluble salt of a sulphonated phenol or a water-soluble phenate.  An alkali such as sodium carbonate may also be present, and the sulphonate may be the sodium salt of a sulphonated commercial cresylic acid.  The phenate may be a sodium phenate derived from commercial cresylic acid and the organic solvent may be diethylene glycol or mono or dimethyl cyclo-hexanol.  The nonphenolic component of the detergent may be an alkyl aryl sulphonate or a surface-active sodium salt of an alkyl ester of sulphuric acid.  In an example 2.5 per cent by weight of a degreasant comprising 50 lbs. of the sodium salt of sulphonated commercial cresylic acid, 30 lbs. of diethylene glycol and 20 lbs. of water, or 0.75 per cent by weight of a degreasant comprising 50 lbs. of "Teepol," 75 lbs. of the sodium salt of sulphonated commercial cresylic acid, 12 lbs. of dimethyl cyclohexanol and 30 lbs. of water is added to a solution of 1 1/2 per cent by weight anhydrous sodium chromate and 5 per cent anhydrous sodium carbonate in 93 1/2 per cent water. Heavily greased aluminium sheets are degreased and oxide coated by immersion in a bath of the above liquid for 7 minutes at 95 DEG C. Reference is made in the first Provisional Specification to the use of sulphated long chain fatty alcohols as detergents.