Patent ID: 8414753
Filing Date: 2013-04-09
Classification: C08K,C09D,C25D

Abstract:
1. A method for forming a coating film on a metallic substrate by a multistage energization method at no less than two stages, characterized by using an electrodeposition bath which comprises a water-based film-forming agent (I) comprising 30-20,000 ppm in terms of the metallic mass of zirconium compound (A) and, as the base resin, an amino group-containing modified epoxy resin (B) which is obtained through reaction of an epoxy resin (a) with an amino group-containing compound (b), said epoxy resin (a) having been obtained through reaction of a diepoxide compound (a1) represented by the following formula (1): [in the formula, n is an integer of 1-50], a bisphenol epoxy resin (a2) and bisphenols (a3), wherein the first stage electrocoating is conducted by energizing at a coating voltage (V 1 ) of 1-50 V for 10-360 seconds with the metallic substrate serving as the cathode, and the second and subsequent stage electrocoating is conducted by energizing at a coating voltage (V 2 ) of 50-400 V for 60-600 seconds with the metallic substrate serving as the cathode, the difference between the coating voltage (V 2 ) and the coating voltage (V 1 ) being not less than 10 V.