Can CED coatings withstand UV radiation?

A. Epoxies do not have UV resistance and they chalk when exposed to sunlight.

Acrylic, Polyester and Polyurethane based coatings have excellent UV resistance but not the same corrosion resistance.

To get over the problem, where ever technically required, Epoxy E-coat is used as a primer and then a topcoat of UV resistant paint is applied.

This is not required for under the bonnet or chassis automotive parts and therefore black epoxy CED works perfectly well there. Some manufacturers use Epoxy CED for wipers and the chalking is visible soon.

Hope this helps.

Thank you Mr. Gurvin Singh for the clarification.

Q. Can anyone help me in getting the statistical information as a comparative outlook between epoxy and other coatings on UV durability and its properties?

A. Dear Mr. Narasimhun,

Now there are cathodic e-coats available having UV resistance they are

1. Acrylic CED : These are products having 500 hr salt spray, are glossy and having high coverage but costlier.

2.Polyester CED : Having less salt spray than acrylic CED.

The exact data for comparison with conventional Epoxy CED can be given by renowned suppliers of CED.

Hope this will help you to start up.

Regards,

Thanks Mr. Suhas.S.Mahajan. I will get the exact data from the suppliers.

A. Hi, Cherhan. Yes, they are. Also electrocoating, electropainting, electrophoretic deposition, and electrophoretic lacquering. I rarely hear of anodic electrodeposition anymore and my assumption is that it has largely been supplanted by CED.

Regards,

A. Dear Mr Redford,

If you are using an acrylic based CED process you need not worry about UV degradation. In any case, even if your parts are going through about a months time of sun light exposure; I don't foresee any problems with top coating over an epoxy based CED also. The epoxies are a very robust and adherent coating and can be topcoated even after one year's indoor storage without any adhesion related issues cropping up.
Try and see -- theory guides but experiment decides.

"Electrocoating: a Guidebook for Finishers"
by Electrocoat Association

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A. Hi Ben. There may be some misunderstandings on your end, or I may simply be misreading your posting. I'm assuming that the 'powder' you are referring to is powder that is chalking off of the e-coating. If the coating is excessively chalking under UV light, it is probably an epoxy coating (these are not UV resistant). The powder would not be AlO(OH)2 though; it would be some sort of organic related to the epoxy such as a bisphenol. I suspect that the evaporator coil is aluminum, and that's where the idea of aluminum oxides and hydroxides is coming from; but aluminum should not be coming into play until the paint is gone.

I realize that you are an HVAC tech rather than a metal finisher, and may not be able to personally address putting a proper coating on this coil, but I think the e-coat should be considered a primer, perhaps acceptable if the coil sees no sunlight or UV, but which must be topcoated (perhaps with a polyester powder coating) for exposure to sunlight or UV. Good luck.

Regards,

A. Hi Manoj. We appended your query to an earlier thread which explains that CED is a method of applying a coating, but it is the nature of the coating (epoxy, polyester, acrylic) rather than the application method which determines its UV resistance. Good luck.

Regards,

A. Dear Chandan,
Epoxy CED or Acrylic CED application depends on the characteristics required for the coating. If we need durability, where UV resistance does not matter we use epoxy-based CED; but in case of UV resistance we use Acrylic CED. It's only thumb rules; there are 36 properties which can be compared and we can select which type CED is required for our product.

A. Hi Vaibhav. We appended your inquiry to a thread where Gurvin, Suhas, Khozem, and Anurag have between them given us an excellent education on this. Acrylic e-coat will be more expensive than epoxy and deliver less corrosion resistance. And while e-coat may do well in a salt spray test, I suspect that the real world will quickly disabuse us of the idea of acrylic e-coat being equal to epoxy e-coat plus powder coating. It may be "good enough" but we don't have any info about the application or environment to let us hazard a guess.

Luck & Regards,

A. A "BIG NO".
No, you don't do it.