Method for forming coating film on constant velocity universal joint

A method of forming a coating film on a surface of a metal automotive part, comprising:

• a powder-coating step in which a powder is deposited by powder-coating on the surface of the metal automotive part that has been quenched after forging, and
• a tempering and bake-hardening step in which tempering of the metal automotive part and bake-hardening of the deposited powder are performed simultaneously,
• wherein the surface of the metal automotive part before the powder is deposited thereon is a work-hardened basis material surface,
• wherein in the powder-coating step, the powder is deposited on a surface which is a material surface that has not been subjected to a chemical conversion film treatment and has been cleaned using an alkaline detergent at a temperature of 50 to 80° C.,
• wherein the alkaline detergent is composed of an alkaline aqueous solution, that can remove non-reactive soap layers or reactive soap layers remaining on the surface of the metal automotive part that has been quenched after forging, contains a surfactant and
• wherein adhesion of the coating film to the material surface is increased by alkali treatment alone without formation of the chemical conversion film.