Method for forming multi-layered coating film

A method for forming a multilayer coating film, the method consisting essentially of:

• Step 1:
• immersing a metal substrate in a chemical conversion treatment solution to form a chemical conversion coating film;
• performing a water-washing step;
• and optionally subjecting the metal substrate to at least one of air blowing, shaking, and rotating, and
• Step 2:
• performing electrodeposition coating on the metal substrate which has been subjected to the chemical conversion of Step 1, by using a cationic electrodeposition coating composition to form an electrodeposition coating film,
• wherein the chemical conversion treatment solution contains no less than 5 ppm and less than 50 ppm of sodium ions, no less than 5 ppm and less than 90 ppm of calcium ions, less than 100 ppm of potassium ions, and less than 90 ppm of magnesium ions on a mass basis,
• wherein the chemical conversion treatment solution comprises hexafluorozirconic acid,
• wherein the chemical conversion treatment solution is used continuously,
• wherein the water-washing step is performed in one step, and
• wherein the cationic electrodeposition coating composition contains an amino group-containing epoxy resin (A) and a blocked polyisocyanate (B),
• the amino group-containing epoxy resin (A) being contained in an amount of 40 to 90 mass %, and the blocked polyisocyanate (B) being contained in an amount of 10 to 60 mass %, based on the total resin solids content,
• wherein the chemical conversion treatment solution contains 150 to 2,000 ppm of at least one metal compound component (M) comprising at least one metal compound selected from zirconium, titanium, cobalt, aluminum, vanadium, tungsten, molybdenum, copper, zinc, indium, bismuth, yttrium, iron, nickel, manganese, gallium, silver, and lanthanoid metals, as the total metal content on a mass basis.