UV rating of an epoxy coating?

[awol]

Is there a standard test to rate the performace of an epoxy coating that is designed to be a UV protection coating? I found companies that rate their own coating as " good UV protection" but what does that mean?

We use a coating as a sacrificial part of the system and it contains pigments to block the sun. Weather and erosion knock the chalked surface loose and affect the life of the coating. We monitor the coating and when it gets thin, we re-coat.

But how is the effectiveness of the UV protection measured?
I thought it either blocked the sun or it didn't. Is there a test to rate these coating systems?

 

[TVP]

There are many tests to measure resistance of coatings to certain environments. ASTM D 4214, D 5065, and D 4587, ISO 11507 and 11997-2 are a few related to UV resistance. ASTM G 151 and G 154 are methods for conducting UV exposure tests. Use the following links to review the standards:

http://www.astm.org/Standard/index.shtml

http://www.iso.org/iso/home.htm

 

[IRstuff]

it either blocked the sun or it didn't

Instantaneously, yes. However, UV light is more energetic than its visible counterpart, and anything organic will ge degraded over time with UV exposure. That's why testing is more about lifetime than instantaneous efficacy.

The fact that you described your coating as "sacrificial" demonstrates the intent of the coating is to absorb and block the UV damage with something that can be allowed to be degraded to protect something that is not allowed to be degraded.

TTFN

FAQ731-376

 

[Compositepro]

In general, epoxies do not have a good resistance to u.v. They will yellow and chalk. Additives will make the coating last longer. The fact that the coating is degrading means it is absorbing the u.v. energy rather than letting it through. The coating does not have to degrade to protect what is underneath. Urethanes are much more common top coats. All organic materials will eventually degrade, however.

 

[SJones]

The question isn't about resistance; it's about UV absorption (or transmittance depending on which way you want to look).

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

 

[IRstuff]

Tey Kynar, if you can use it. It's used for aluminum siding and roofs. Supposedly has a 25-yr life in those applications.

TTFN

FAQ731-376