Method of improving the corrosion resistance of a metal substrate

Patent metadata

Field	Value
Publication number	US-10697081-B2
Application number	US-201816015861-A
Country	US
Kind code	B2
Filing date	Jun 22, 2018
Priority date	Jun 22, 2018
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

The invention provides a method of improving the corrosion resistance of a metal substrate. The method comprises:
(a) electrophoretically depositing on the substrate a curable electrodepositable coating composition to form a coating over at least a portion of the substrate, and (b) heating the substrate to a temperature and for a time sufficient to cure the coating on the substrate. The electrodepositable coating composition comprises a resinous phase dispersed in an aqueous medium, the resinous phase comprising:
(1) an ungelled active hydrogen-containing, cationic salt group-containing resin electrodepositable on a cathode; (2) an at least partially blocked polyisocyanate curing agent; and (3) a pigment component comprising an inorganic, platelike pigment having an average equivalent spherical diameter of at least 0.2 microns. The electrodepositable coating composition demonstrates a pigment-to-binder ratio of at least 0.5. The coating composition contains less than 8 percent by weight of a grind vehicle.

First claim

Therefore, we claim:

1. A method of improving the corrosion resistance of a metal substrate comprising:
(a) electrophoretically depositing on the substrate a curable electrodepositable coating composition to form an electrodeposited coating over at least a portion of the substrate, the electrodepositable coating composition comprising a resinous phase dispersed in an aqueous medium, said resinous phase comprising:
(1) an ungelled active hydrogen-containing, cationic salt group-containing resin electrodepositable on a cathode;
(2) an at least partially blocked polyisocyanate curing agent; and
(3) a pigment component, wherein the pigment component comprises an inorganic, platelike pigment having an average equivalent spherical diameter of at least 0.2 microns; and wherein the inorganic platelike pigment is present in the resinous phase in an amount such that the electrodepositable coating composition demonstrates a pigment-to-binder ratio of at least 1; and wherein the electrodepositable coating composition contains less than 8 percent by weight of a grind vehicle, based on the total weight of solids in the electrodepositable coating composition; and

(b) heating the substrate to a temperature and for a time sufficient to cure the electrodeposited coating on the substrate.

2. The method of claim 1 , wherein the cationic salt group-containing resin (1) is prepared from a polyepoxide polymer, an acrylic polymer, a polyurethane polymer, and/or a polyester polymer.

3. The method of claim 1 , wherein the cationic salt group-containing resin (1) contains cationic amine salt groups.

4. The method of claim 1 , wherein the inorganic, platelike pigment comprises clay.

5. The method of claim 4 , wherein the inorganic, platelike pigment comprises kaolin clay having an average equivalent spherical diameter of 0.2 to 5.0 microns.

6. The method of claim 5 , wherein the kaolin clay has an average equivalent spherical diameter of 0.2 to 3.5 microns.

7. The method of claim 1 wherein the curable electrodepositable coating composition is essentially free of a grind vehicle.

8. The method of claim 7 wherein the pigment component is dispersed in the cationic salt group-containing resin (1) prior to dispersion of the resinous phase into the aqueous medium.

Assignees

• Ppg Ind Ohio Inc

Inventors

• Bezer Silvia
• Zawacky Steven R
• Puodziukynaite Egle

Classifications

• C25D13/04 Primary

  with organic material · CPC title

• C23F11/173

  Macromolecular compounds · CPC title

• C09D5/4457

  containing special additives, e.g. pigments, polymeric particles · CPC title

• C09D5/44 Primary

  for electrophoretic applications (processes for coating by electrophoresis C25D13/00) · CPC title

• C09D5/4465

  Polyurethanes · CPC title