Electrodeposition of an autodepositable polymer

Patent metadata

Field	Value
Publication number	US-9115442-B2
Application number	US-201313834961-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Mar 15, 2013
Publication date	Aug 25, 2015
Grant date	Aug 25, 2015

Abstract

Coating bath compositions and processes useful in depositing organic polymeric coatings on metal substrates at low voltages are provided, the baths comprising one or more dispersed organic film forming polymers; and an etchant; wherein the principle film forming polymer is stabilized in the bath by the presence of anionic surfactant, but can be readily anodically deposited under low voltage. The invention also relates to processes of depositing a coating and metal substrates coated using the baths and processes of the invention.

First claim

What is claimed is:

1. An anodic electrodeposition bath composition comprising: water, an anodically electrodepositable polymeric dispersion stabilized by anionic surfactant; an etchant system comprising an acid, and optionally an oxidizing agent; wherein the etchant system is present in a concentration less than a threshold concentration required to result in autodeposition of a coating formed from the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant in the absence of applied electrical current.

2. The anodic electrodeposition bath composition according to claim 1 , wherein the acid is selected from organic and inorganic acids in a concentration sufficient to provide a pH of less than 4.

3. The anodic electrodeposition bath composition according to claim 1 , wherein said etchant system comprises hydrofluoric acid (HF) and ferric iron ions dissolved in said hydrofluoric acid, said ferric iron ions being present in an amount ranging from 0.015-0.3 g/l.

4. The anodic electrodeposition bath composition according to claim 1 , wherein the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant comprises polymers having a weight average molecular weight of 100,000 to 1 million Daltons.

5. The anodic electrodeposition bath composition according to claim 1 , wherein weight average molecular weight of all polymeric constituents of the anionically stabilized polymeric dispersion taken together is greater than or equal to 100,000 Daltons.

6. The anodic electrodeposition bath composition according to claim 1 , wherein 10% to 50% by weight of the polymeric constituents based on total polymeric constituents of the anionically stabilized polymeric dispersion are greater than 100,000 Daltons.

7. The anodic electrodeposition bath composition according to claim 1 , wherein the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant is present at a concentration of approximately 1-20 wt % solids based on total solids.

8. The anodic electrodeposition bath composition according to claim 1 , wherein the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant comprises polymers selected from the group consisting of acrylic, epoxy, epoxy-acrylic, polyurethane, and vinyl based polymers.

9. The anodic electrodeposition bath composition according to claim 1 wherein the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant comprises polymer particles comprising epoxy polymer and acrylic polymer.

10. The anodic electrodeposition bath composition according to claim 1 wherein the anodically electrodepositable polymeric dispersion stabilized by anionic surfactant is polymerized by miniemulsion and comprises portions of acrylic polymer and portions of epoxy polymer.

11. The anodic electrodeposition bath composition according to claim 1 , further comprising one or more pigments selected from the group consisting of carbon black, titanium dioxide, green pigment, yellow pigment, red pigment and blue pigment.

12. The anodic electrodeposition bath composition according to claim 1 , further comprising an added component of dissolved metallic element selected from one of Groups 2-14 and optionally phosphate ions.

13. The anodic electrodeposition bath composition according to claim 1 , further comprising phosphate ions; a dissolved element selected from the group consisting of Zr, Hf, Al, Ge, B and Sn.

14. A method of generating a uniform anodic electrodeposition coating on a metal substrate comprising steps of:
a. Optionally, cleaning a metal substrate comprising metal surfaces of at least one metal selected from the group consisting of ferrous metals, zinciferous metals, aluminum, magnesium, and alloys thereof;
b. Providing the anodic electrodeposition bath according to claim 1 ,
c. Providing a cathode in contact with said bath;
d. Placing the metal substrate as an anode in said bath; and
e. Passing a current of 0.5-100 volts through the anodic electrodeposition bath for a sufficient amount of time to produce a uniform anodic electrodeposition uncured coating on the metal substrate having a film coating thickness of from about 1 to about 50 microns;
f. Optionally rinsing the uniform anodic electrodeposition coated metal substrate.

15. The method according to claim 14 , wherein the rinsing step f), optionally comprising a plurality of rinsing substeps, is performed with one or more rinses selected from heated water, unheated water, and an aqueous solution comprising a reaction rinse.

16. The method according to claim 15 , wherein, the rinsing step f) comprises a plurality of rinsing substeps, said substeps each being performed with one of said rinses selected from heated water, unheated water, and an aqueous solution comprising a reaction rinse.

17. The method according to claim 14 , further comprising an additional step of heating the coated metal substrate at a temperature of greater than 100° C. for a time sufficient to cure the uniform anodic electrodeposition coating.

18. The method according to claim 17 , wherein the heating step comprises a sub-step wherein the uncured coating is dewatered and then a paint is applied to the dewatered uncured coating on the metal substrate, with or without a reduction in temperature during the sub-step, followed by further heating for a time sufficient to co-cure the uncured coating and the paint.

19. The method according to claim 14 , wherein the metal substrate is a multi-metal substrate comprising metal surfaces of at least two of said metals wherein said at least two of said metal are dissimilar metal having different activity levels; said multi-metal substrate further comprising interfaces of the dissimilar metals and step e) deposits said coating by destabilization of cations, electrically and chemically generated, thereby providing coatings uniformly deposited over said interfaces.

20. The method according to claim 14 , wherein the anodic electrodeposition bath further comprises an added component of dissolved metallic element, different from the metal substrate, selected from one of Groups 2-14 and optionally phosphate ions.

21. The method according to claim 20 , further comprising forming an integral conversion coating during anodic electrodeposition step e), said integral conversion coating comprising the dissolved metallic element, different from the metal substrate, selected from one of Groups 2-14; and/or a reaction product of said dissolved metallic element with said metal surfaces.

Assignees

• Henkel Ag & Co Kgaa

Inventors

• Nadupparambil Sekharen Manesh
• Dolan Shawn E
• Marvin Brian J
• Ahmed Bashir M
• Mcgee John D
• Abu-Shanab Omar L
• Hickey Derek A

Classifications

• C25D11/02 Primary

  Anodisation · CPC title

• C09D7/125

  Chemistry & Metallurgy · mapped topic

• C09D7/1216

  Chemistry & Metallurgy · mapped topic

• C25D9/02

  with organic materials · CPC title

• C09D5/4484

  Anodic paints (C09D5/4403 - C09D5/4476 take precedence) · CPC title