Patent ID: 7625476

Claim:
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, wherein (i) the film-forming agent comprises 30-20,000 ppm, in terms of the total amount of metals (as converted to mass), of zirconium compound optionally, a compound containing at least one metal (a) which is selected from the group consisting of 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, (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 of 50-400 V for 60-600 seconds, using the metal substrate as the anode.