SE7513670L - COATING BATH FOR CATAFORETIC METAL SURFACE COATING - Google Patents

Abstract

1469068 Electrocoating compositions BASF FARBEN & FASERN AG 27 Nov 1975 [5 Dec 1974] 48855/75 Headings C3B and C3P [Also in Division C7] A cataphoretic coating is produced on a ferrous metal (iron or steel) surface by connecting it as cathode in a coating bath including an aqueous solution and/or dispersion of a salt of a cationic film forming agent, and a soluble metal salt, e.g. sulphate, nitrate, acetate, formate, lactate, phosphate or chloride of Cu, Ag, Co, Cd, Ni, Sn, Sb, Zn or Cr, to produce metal ions, e.g. in a concentration between 1 and 2000 p.p.m. based upon the film forming agent, whose potential in the electrochemical series is higher than that of the ferrous metal, or which are capable of deposition on the surface as the result of an overvoltage, then stoving the coating formed, e.g. at 80‹ to 250‹ C. Prior to coating, the surface may be immersed in or spraying with the coating bath, and may be zinc phosphated. Preferably auxiliary anodes of the same metal are used for maintaining the metal ion concentration constant. The film forming agent may be a reaction product of an epoxy resin with a Mannich base consisting of a condensed phenol, a secondary amine having a hydroxyalkyl group (e.g. di-2-methoxyethylamine and diethanolamine) and formaldehyde; a reaction product of an epoxy resin with a diisocyanate; or a copolymerisate in which 3 to 50% of at least one mono- or bicyclic compound having a 5- or 6- membered heterocycle containing 1 to 3 heteroatoms of which one is N carrying a vinyl group, 3 to 30% of at least one amide, (oxy)alkylamide and/or oxyalkylamide of (meth)acrylic acid, and 20 to 94% of at least one alkyl ester of (meth)- acrylic acid and/or at least one (alkyl)vinylbenzene (optionally with the addition of not more than 30% of at least one ethylene unsaturated comonomer) are incorporated by polymerization. The film forming agent can be dissolved or dispersed in water by combination with an acid, e.g. HCl, H 2 SO 4 , H 3 PO 4 , acetic, formic, citric, lactic, maleic or phthalic acid (or anhydrides thereof). Other resins capable of cataphoretic deposition may be mixed with the film forming agent: e.g. amino or phenolic condensates, epoxy or alkyl resins and/or polyurethanes. Pigments, e.g. talcum and soot, fillers, hardening catalysts, flow and adhesion improving and anti-foaming agents, solvents such as isopropanol and butanol, tetrahydrofuran, aliphatic and/or aromatic hydrocarbons, esters/ ethers may also be added.