process for the preparation of metal surfaces for the application of protective coatings

摘要

Metal surfaces are prepared for application of a protection coating by (a) contacting them with an aq. soln contg at least 1 wt/vol. % critic gluconic, tartaric, oxalic, glycollic glucoheptonic, malic, formic, acetic, or EDTA acid or their mixts, the acid contg. sufficient nitrogeneous base to give a pH of 2.5-6 and an emulsifying compsn contg a water soluble org. solvent and a surfactant, so that the surfaces are practically free of deposits of iron oxide and foreign malts and (b) adjusting the pH to 5.5-7.5, adding an oxidising agent and aerating the surfaces until they are practically free of magnetic. Prepn of large surfaces prior to painting such as the hold of a ship esp. holds carrying petroleum products mineral or vegetable oil etc. The appearance of rust and other impurities is inhibited for several days, i.e. long enough for passivation and painting to be effected.