Multi-layered coating film formation method

Patent metadata

Field	Value
Publication number	US-2016153107-A1
Application number	US-201414906018-A
Country	US
Kind code	A1
Filing date	Aug 8, 2014
Priority date	Aug 13, 2013
Publication date	Jun 2, 2016
Grant date	—

Abstract

A problem to be solved by the present invention is to provide a method for forming a multilayer coating film, the method being capable of achieving excellent finished appearance and excellent corrosion resistance without affecting electrodeposition coatability even when a part or all of the water-washing step is omitted after chemical conversion treatment, and to provide a coated article. The invention provides a method for forming a multilayer coating film, comprising forming a chemical conversion coating film and an electrodeposition coating film on a metal substrate by Step 1 of immersing a metal substrate in a chemical conversion treatment solution to form a chemical conversion coating film, and Step 2 of omitting a part or all of the water-washing step, and performing electrodeposition coating on the metal substrate using a cationic electrodeposition coating composition to form an electrodeposition coating film, wherein when the electrodeposition coating is performed in Step 2, the solution adhered to and/or deposited on the metal substrate has an electrical conductivity of less than 10,000 μS/cm.

First claim

1 . A method for forming a multilayer coating film, the method comprising forming a chemical conversion coating film and an electrodeposition coating film on a metal substrate by the following steps:
Step 1: immersing a metal substrate in a chemical conversion treatment solution to form a chemical conversion coating film; and Step 2: performing electrodeposition coating on the metal substrate by using a cationic electrodeposition coating composition to form an electrodeposition coating film, wherein when the electrodeposition coating is performed in Step 2, the solution adhered to and/or deposited on the metal substrate has an electrical conductivity of less than 10,000 μS/cm.

2 . The method for forming a multilayer coating film according to claim 1 , wherein in Step 2, a part or all of the water-washing step before electrodeposition coating is omitted.

3 . The method for forming a multilayer coating film according to claim 1 , wherein when the electrodeposition coating is performed in Step 2, the solution adhered to and/or deposited on the metal substrate has an electrical conductivity of more than 60 μS/cm and less than 7,000 μS/cm.

4 . The method for forming a multilayer coating film according to claim 1 , wherein the solution adhered to and/or deposited on the metal substrate contains less than 500 ppm of sodium ions, based on the mass of the solution.

5 . The method for forming a multilayer coating film according to claim 1 , wherein the solution adhered to and/or deposited on the metal substrate contains less than 500 ppm of potassium ions, based on the mass of the solution.

6 . The method for forming a multilayer coating film according to claim 1 , wherein the solution adhered to and/or deposited on the metal substrate contains less than 500 ppm of calcium ions, based on the mass of the solution.

7 . The method for forming a multilayer coating film according to claim 1 , wherein the solution adhered to and/or deposited on the metal substrate contains less than 500 ppm of magnesium ions, based on the mass of the solution.

8 . The method for forming a multilayer coating film according to claim 1 , wherein the chemical conversion treatment solution contains 30 to 20,000 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.

9 . The method for forming a multilayer coating film according to claim 1 , wherein the chemical conversion solution contains a zirconium compound.

10 . The method for forming a multilayer coating film according to claim 1 , wherein the chemical conversion treatment solution contains a water-dispersible or water-soluble resin composition (P) in an amount of 0.01 to 40 mass %.

11 . The method for forming a multilayer coating film according to claim 1 , 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.

12 . The method for forming a multilayer coating film according to claim 1 , wherein the metal substrate is subjected to at least one of air-blowing, shaking, and rotating, before performing electrodeposition coating in Step 2.

13 . A coated article having a multilayer coating film formed by using the method for forming a multilayer coating film of claim 1 .

Assignees

• Kansai Paint Co Ltd

Inventors

• Nemoto Yukihiro
• Matsuda Hideki

Classifications

• C23C22/34

  containing fluorides or complex fluorides · CPC title

• C09D5/4453

  characterised by the nature of the curing agent · CPC title

• C23C22/48

  not containing phosphates, hexavalent chromium compounds, fluorides or complex fluorides, molybdates, tungstates, vanadates or oxalates · CPC title

• C25D13/12

  characterised by the article coated · CPC title

• C23C22/36

  containing also phosphates · CPC title