Method of improving the corrosion resistance of a metal substrate

Patent metadata

Field	Value
Publication number	US-11905610-B2
Application number	US-202016846457-A
Country	US
Kind code	B2
Filing date	Apr 13, 2020
Priority date	Jun 22, 2018
Publication date	Feb 20, 2024
Grant date	Feb 20, 2024

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. An 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;
(2) an at least partially blocked polyisocyanate curing agent; and
(3) a pigment component, wherein the pigment component comprises an inorganic, platelike pigment present in the resinous phase in an amount such that the electrodepositable coating composition demonstrates a pigment-to-binder ratio of at least 0.5,
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.

2. The electrodepositable coating composition of claim 1 , wherein the inorganic, platelike pigment has an average equivalent spherical diameter of at least 0.2 microns.

3. The electrodepositable coating composition of claim 1 , wherein the cationic salt group-containing resin comprises a polyepoxide polymer, an acrylic polymer, a polyurethane polymer, and/or a polyester polymer.

4. The electrodepositable coating composition of claim 1 , wherein the cationic salt group-containing resin contains cationic amine salt groups.

5. The electrodepositable coating composition of claim 1 , Wherein the inorganic, platelike pigment comprises clay and/or talc.

6. The electrodepositable coating composition of claim 5 , wherein the inorganic, platelike pigment comprises talc having an average equivalent spherical diameter of 0.6 to 1.9 microns.

7. The electrodepositable coating composition of claim 1 , wherein the inorganic, platelike pigment comprises kaolin clay having an average equivalent spherical diameter of 0.2 to 5.0 microns.

8. The electrodepositable coating composition of claim 7 , wherein the electrodepositable coating composition demonstrates a pigment-to-binder ratio of at least 1.

9. The electrodepositable coating composition of claim 1 , wherein the kaolin clay has an average equivalent spherical diameter of 0.2 to 3.5 microns.

10. The electrodepositable coating composition of claim 1 , wherein the electrodepositable coating composition is essentially free of a grind vehicle.

11. The electrodepositable coating composition of claim 1 , wherein the pigment component is dispersed in the cationic salt group-containing resin prior to dispersion of the resinous phase into the aqueous medium.

12. A method of improving the corrosion resistance of a metal substrate comprising:
(a) electrophoretically depositing on the substrate the electrodepositable coating composition of claim 1 to form an electrodeposited 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 electrodeposited coating on the substrate.

13. The method of claim 12 , wherein the cationic salt group-containing resin comprises a polyepoxide polymer, an acrylic polymer, a polyurethane polymer, and/or a polyester polymer.

14. The method of claim 12 , wherein the inorganic, platelike pigment comprises clay and/or talc.

15. The method of claim 12 , wherein the electrodepositable coating composition is essentially free of a grind vehicle.

16. The method of claim 12 , wherein the pigment component is dispersed in the cationic salt group-containing resin prior to dispersion of the resinous phase into the aqueous medium.

17. The method of claim 12 , further comprising applying a pretreatment composition over at least a portion of the metal substrate prior to electrophoretically depositing the electrodepositable coating composition on to the metal substrate.

18. A metal substrate coated by the method of claim 12 .

Assignees

• Ppg Ind Ohio Inc

Inventors

• Bezer Silvia
• Zawacky Steven R
• Puodziukynaite Egle

Classifications

• C25D13/04 Primary

  with organic material · CPC title

• C09D5/4438

  Binder based on epoxy/amine adducts, i.e. reaction products of polyepoxides with compounds containing amino groups only · CPC title

• C09D5/4453

  characterised by the nature of the curing agent · CPC title

• C09D5/4457

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

• C09D7/68

  Particle size between 100-1000 nm · CPC title