Patent ID: 8273189

Claim:
A method of conversion by carboxylation of a metal surface selected from the group consisting of zinc, iron, aluminium, copper, lead and their alloys, and galvanized, electrozinced, aluminized, and copper-plated steels, under oxidizing conditions in relation to the metal surface, by bringing said metal surface into contact with a aqueous or hydro-organic bath containing a mixture of organic acids, said mixture being such that: said organic acids are saturated linear carboxylic acids having from 10 to 18 carbon atoms, said mixture is a binary or ternary mixture of said organic acids, said mixture is present in said bath in a concentration of 20 g/l or more, said organic acids are present in said mixture in respective ratios such that: for a mixture of two acids, the deviation in composition does not exceed 5% in relation to a binary eutectic x/y, x and y being, in molar percentages, the respective ratios of said two acids in said binary eutectic, for a mixture of three acids, the deviation in composition does not exceed 3% in relation to a ternary eutectic x/y/z, x, y and z being, in molar percentages, the respective ratios of said three acids in said ternary eutectic.