Surface treatment of metal article by water-soluble (film-forming) material

Claim 1

A SURFACE TREATING METHOD FOR A METAL ARTICLE TO PRODUCE A FILM THEREON BY APPLYING THERETO A WATER-SOLUBLE FILM FORMING MATERIAL, WHICH COMPRISES: (I) PROVIDING A AQUEOUS SOLUTION, THE SOLUTE OF WHICH CONSISTS ESSENTIALLY OF (A) A WATER-SOLUBLE ORGANIC HIGH POLYMER SELECTED FROM THE GROUP CONSISTING OF A PARTIALLY HYDROLYZED POLYVINYL ACETATE; A POLYVINYL ALCOHOLA POLYMETHYLOL UREA; A POLYMETHYLOL MELAMINE; A POLYMETHYLOL PHENOL; A POLYALKYLVINYLETHERMALEIC ACID COPOLYMER; A POLYMALEIC ACID-ETHYLENE COPOLYMER; A POLYMALEIC ACID-VINYL ACETATE COPOLYMER; APOLYACRYLIC ACID, A POLYMETHACRYLIC ACID, A COPOLYMER OF POLYACRYLIC ACID AND METHACRYLIC ACID; AND (B) A WATER-SOLUBLE COMPOUND SELECTED FROAM THE GROUP CONSISTING OF CHROMIUM COMPOUNDS OF TRIVALENT AND HEXAVALENT CHROMIUM IN AN AMOUNT OF ABOUT 0.01% TO 20% BY WEIGHT BASED ON THE WEIGHT OF SAID SOLUTION, (C) AN ACIDIFYING AGENT SELECTED FROM THE GROUP CONSISTING OF BORIC ACID, PHOSPHORIC ACID AND ACIDIC SALTS OF SAID ACIDS IN AN AMOUNT OF ABOUT 0.01% TO 20% BY WEIGHT BASED ON THE WEIGHT OF THE SOLUTION, THE SAID SOLUTION HAVING A PH OF FROM 0.5 TO 7.0 AND A VISCOSITY OF 1 TO 1000 CENTIPOISES AT A TEMPERATURE OF FROM 15 TO 80*C., (II) INTRODUCING AN ARTICLE OF A METAL SELECTED FROM THE GROUP CONSISTING OF IRON, TIN, ZINC, ALUMINUM AND MAGNESIUM IN SAID SOLUTION, (III) SUBJECTING SAID ARTICLE IN SAID SOLUTION TO ELECTROLYSIS AS A CATHODE. (IV) WITHDRAWING THE ARTICLE FROM SAID SOLUTION AND HEATING THE SAME TO DRY AT A TEMPERATURE OF FROM 100* TO 300*C.