Electrodeposition of resinous, film-forming coatings

摘要

A surface is coated electro-phoretically by (1) applying thereto an electrically conductive layer comprising conductive particles, e.g. C, Zn, Ni, Al, Cr, Mn, Cu, Cd or steel, in a carrier such as water, organic solvent or resinous binder, and (2) employing the coated surface as an electrode in an electro-phoretic deposition process using another conductive electrode wherein the electrodes are in contact with an aqueous bath containing an electro-depositable resinous film-forming coating composition. Such a composition may comprise (a) an at least partially neutralized reaction product of a drying oil fatty acid ester and an alpha, beta-ethylenically unsaturated dicarboxylic acid or anhydride, (b) an at least partially neutralized interpolymer of an unsaturated carboxylic acid and a hydroxalkyl ester thereof, and an amine-aldehyde resin and/or polyepoxide, or (c) an alkyd resin and an amine-aldehyde resin. Many examples are specified of resinous binder for the conductive particles, and of electro-depositable coating composition. Either may contain pigments, e.g. iron oxides, lead oxides, SrCO3, carbon black, TiO2, talc, BaSO4, cadmium yellow or red or chromic yellow, and other additives such as dispersing agents e.g. oil-soluble sulphonate and non-ionic surfactant, and colloidal silica. Multiple coatings may be obtained by repeating the steps (1) and (2). The surface may be conductive, e.g. of steel, Al or Cu, or non-conductive, e.g. of wood, plastics or paper. A metal surface may be provided with an electro-deposited primer coating.