Patent ID: 8075708

Claim:
A cation electrodeposition method which comprises conducting surface treatment on a metal material for automobile body and automobile parts by a chemical conversion coating agent to form a chemical conversion coat, then washing the metal material with water without drying, which is coated with the chemical conversion coat, and then conducting cation electrodeposition coating on the chemical conversion coat, wherein the chemical conversion coating agent comprises: at least one member selected from the group consisting of zirconium, titanium and hafnium having a content of 50 to 2000 ppm on the basis of metal; and fluorine; and at least one member selected from the group consisting of amino group-containing silane coupling agent, hydrolysates thereof and polymers thereof; and having substantially no phosphate ion, said at least one member is selected from the group consisting of amino group containing silane coupling agent, hydrolysates thereof and polymers thereof, has a content of 50 to 500 ppm as a concentration of solid matter, said chemical conversion coating agent has a pH of 1.5 to 6.5, and said metal material comprises at least iron material.