COATING METHOD BY ELECTRODEPOSITION

摘要

PURPOSE:To improve the corrosion and filiform erosion resistances of the edge of a body to be coated by successively carrying out coating with a cationic electrodeposition paint contg. a pigment having a specified oil absorption and coating with an emulsion type electrodeposition paint having a specified min. current density for electrodeposition. CONSTITUTION:A body to be coated is coated by electrodeposition with a cationic electrodeposition paint prepd. by blending a resin A with pigments B including >=5wt.% pigment having >=100 oil absorption so that the total oil absorption of the pigments B is regulated to 1,000-10,000 per 100g resin A. Before the resulting first layer is cured the coated body is further coated by electrodeposition with an emulsion type electrodeposition paint consisting of a resin C and a conventional pigment D having a smaller total oil absorption per 100g resin C than the pigments B and having <=0.7mA/cm<2> min. current density for electrodeposition and >=80wt.% degree of emulsification to form a second layer. The first and second layers are then cured by heating to form a composite cured film. The resin C in the second layer consists of an epoxy type cationic electrodepositable resin E having 40-60dyne/cm surface tension and a nonionic coat forming resin F having 25-45 dyne/cm surface tension in E:F=60:40-98:2 weight ratio.