Method for Forming Surface-Treating Film Verfahren Zur Bildung Eines Films Zur Oberflächenbehandlung Procédé De Formation D’Un Film À Traitement De Surface
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(19) TZZ_ _T (11) EP 1 889 952 B1 (12) EUROPEAN PATENT SPECIFICATION (45) Date of publication and mention (51) Int Cl.: of the grant of the patent: C25D 13/22 (2006.01) C23F 13/04 (2006.01) 30.05.2012 Bulletin 2012/22 C25D 13/18 (2006.01) (21) Application number: 07015508.0 (22) Date of filing: 07.08.2007 (54) Method for forming surface-treating film Verfahren zur Bildung eines Films zur Oberflächenbehandlung Procédé de formation d’un film à traitement de surface (84) Designated Contracting States: (72) Inventors: FR GB • Shimoda, Masaharu Hiratsuka-shi (30) Priority: 08.08.2006 JP 2006215644 Kanagawa-ken 254-0018 (JP) • Okada, Eisaku (43) Date of publication of application: Aichi-Ken 471-8571 (JP) 20.02.2008 Bulletin 2008/08 (74) Representative: Albrecht, Thomas et al (73) Proprietors: Kraus & Weisert • KANSAI PAINT CO., LTD. Patent- und Rechtsanwälte Amagasaki-shi, Hyogo-ken 661-8555 (JP) Thomas-Wimmer-Ring 15 • Toyota Jidosha Kabushiki Kaisha 80539 München (DE) Toyota-shi, Aichi-ken 471-8571 (JP) (56) References cited: EP-A- 1 342 758 EP-A- 1 405 933 EP-A- 1 426 466 EP-A- 1 433 878 Note: Within nine months of the publication of the mention of the grant of the European patent in the European Patent Bulletin, any person may give notice to the European Patent Office of opposition to that patent, in accordance with the Implementing Regulations. Notice of opposition shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). EP 1 889 952 B1 Printed by Jouve, 75001 PARIS (FR) EP 1 889 952 B1 Description Technical Field 5 [0001] This invention relates to a method for forming surface-treating film excelling in corrosion resistance, using a film-forming agent excelling in stability, and to a film structure formed by the method. Background Art 10 [0002] Conventionally, metal substrates for industrial use are given in the course of surface preparation a zinc phos- phate treatment for the purpose of improving corrosion resistance or adherability. However, zinc phosphate treating agent used in the chemical treatment contains large quantities of phosphorus or nitrogen and also contains large quantities of heavy metals such as nickel and manganese for improving the performance of the formed chemical coating, which gives rise to such problems as adverse influences on environments and disposal of industrial waste because the treatment 15 generates a large amount of sludge of zinc phosphate, iron phosphate and the like. [0003] Also for the purpose of improving corrosion resistance of industrial metal substrates, much space and time are required for coating lines for such processing steps as "degreasing - surface treatment - chemical treatment - elec- trodeposition coating". [0004] JP 2003-155578A proposed a chemical treating agent for iron-and/or zinc-based substrates, which contains 20 substantially no phosphate ion but contains zirconium ion and/or titanium ion and fluorine ion. However, the chemical treating agent for iron- and/or zinc-based substrates as described in JP 2003-155578A has a problem in that satisfactory corrosion resistance or finish cannot be secured unless a coating film is applied thereon by a coating step after the treatment using said agent. [0005] International Publication WO 02/103080 pamphlet discloses a technology for reducing the time and space 25 required for the treating steps by the use of a composition for metal surface treatment, which comprises (A) a compound containing at least one metal element selected from Ti, Zr, Hf and Si and (B) a fluorine-containing compound as a supply source of fluorine ion, whereby precipitating a surface treating film excelling in corrosion resistance on a metal surface containing at least either of iron or zinc, and dispensing with a surface adjustment (leveling) step. This surface treating composition disclosed in International Publication WO 02/05860 pamphlet, however, is also subject to the problem of 30 failing to secure satisfactory corrosion resistance or finish, unless a coating film is applied thereon by a coating step after the treatment therewith. [0006] JP 2003-166073A and JP 2003-226982A disclose a surface treating agent for lubricated steel sheet, which contains (A) amine-modified acrylic resin, (B) at least one compound selected from phosphoric acid-derived compounds, hydrofluoric acid, metal hydrofluoric acid and metal hydrofluoric acid salt, and (C) at least one compound selected from 35 molybdenum compound, tungsten compound and vanadium compound; and which, when coated on zinc-plated steel sheet useful for automobile bodies or household electric appliances, can provide lubricated steel sheet excelling in press-shapability and corrosion resistance. However, the steel sheet which is surface treated with the surface treating agent as disclosed in JP 2003-166073A or JP 2003-226982A fails to show satisfactory corrosion resistance or finish unless a coating film is applied thereon by a coating step after the chemical treatment, and the invention cannot achieve 40 reduction in steps or space-saving. [0007] JP 2003-293161A discloses a polymer composition for metal surface treating agent, which comprises a specific copolymer having salicylideneamino group and amino group. The steel sheet treated with the polymer composition for metal surface treating agent as described in JP 2003-293161A again fails to show satisfactory corrosion resistance or finish, unless a coating film is applied thereon by a coating step, and the invention cannot lead to reduction in steps or 45 space-saving. [0008] Furthermore, JP Hei 2(1990)-282499A discloses a method for forming a coating film on apertures of coating object having complex construction such as an automobile body having apertures of not more than 500 mm in width, by cationic electrodeposition coating according to multistage electricity applying method. The method as described in JP Hei 2(1990)-282499A is effective for improving corrosion resistance of a coating object having apertures of not more 50 than 500 mm in width, by coating the apertures, but does not amount to secure satisfactory corrosion resistance or finish. [0009] JP 2003-328192A (EP1342758A) discloses a method for forming multilayer electrodeposition coating film by applying a cationic electrodeposition paint containing plural emulsions among which the differences in quantity of elec- tricity necessary for starting precipitation are unified. This method, however, is yet incapable of providing sufficient corrosion resistance. 55 [0010] Furthermore, European patent application EP 1 426 466 A1 discloses a surface treatment agent for metal, prepared by adding at least one water-soluble resin or water-based emulsion resin selected from among cationic or nonionic urethane, acrylic, epoxy, polyester, and polyamide resins, a particular phenolic resin and a metal compound containing at least one metal selected from the group consisting of Zr, Ti, V, Mo, W, Mn and Co to water as well as a 2 EP 1 889 952 B1 process for surface treatment of metallic substances using the surface treatment agent. [0011] European patent application EP 1 433 878 A1 discloses a chemical conversion coating agent comprising at least one kind selected from the group consisting of zirconium, titanium and hafnium; fluorine; and a water-soluble epoxy compound containing an isocyanate group and/or a melamine group, wherein a content of the at least one kind selected 5 from the group consisting of zirconium, titanium and hafnium in the chemical conversion coating agent is 20 to 10000 ppm in terms of metal, and a content of the water-soluble epoxy compound containing the isocyanate group and/or the melamine group in the chemical conversion coating agent is 5 to 5000 ppm as a concentration of solid matter as well as a surface-treated metal having a chemical conversion coat formed by this chemical conversion coating agent. 10 Disclosure of the Invention [0012] The object of the present invention is to offer a method for forming surface treating film excelling in corrosion resistance of the coated film and in stability of the film-forming agent. [0013] We have engaged in concentrative studies and discovered that the above object could be achieved by applying 15 a specific film-forming agent onto a metal substrate by multistage electricity-applying system, under specific conditions, and come to complete the present invention. [0014] Thus, the present invention provides a method for forming a surface-treating film, which comprises applying a film-forming agent onto a metal substrate by a multistage electricity-applying system comprising at least two stages, the method being characterized in that 20 (i) the film-forming agent comprises 30 - 20,000 ppm, in terms of the total amount of metal (as converted to mass), of zirconium compound and, where necessary, a compound containing at least one metal (a) which is selected from titanium, cobalt, vanadium, tungsten, molybdenum, copper, zinc, indium, aluminum, bismuth, yttrium, lanthanide metals, alkali metals and alkaline earth metals, and 1-40% by mass of an anionic group-containing resin component, 25 (ii) the first stage coating is conducted, in the state that the metal substrate is immersed in the film-forming agent, by applying electricity at a voltage of 1 - 50 V for 10 - 360 seconds, using the metal substrate as the cathode, and (iii) the second and subsequent stage coating is conducted, in the state that the metal substrate is immersed in the film-forming agent, by applying electricity at a voltage