Blisterning on the epoxy coating

[bao2ye]

Hello ,

We got some butterfly valve disc coated with epoxy. After immerge the disc into the water and applied the hydrostatic pressure of 200 psi and put the disc in the water with 200 F, the coating got blisterling problem.

Question:

It is blistering on the coating surface a failure?
After all, the disc works eventhough there are small bubbles on the surface

 

[btrueblood]

...depends, did you want the coating to stay put? If so, yes, I'd say the blisters are a failure.

 

[jordicalvo]

Blisteringmay be produced by two reasons: 1/ the butterfly were put in use before total dry epoxi paint( 72 hours), then the solvent that remaining in the film is responsible of the blistering. 2/What were the surface preparation.

 

[coatingengineer]

Hi.

Let's assume your epoxy-coated valve was free of film imperfection prior to service. Blistering, then, must have occurred from water permeation.

Epoxies are thermally stable to 300 F, it's true. Still, this doesn't ensure the perfect barrier at elevated temperature and pressure.

For starters, identify your coating's thickness. Generally speaking, epoxies included, 10 mils (= 0.010 inch = 250 micrometer) should be a targeted minimum. You see, achieving a 'pin-hole-free' surface is key.

Consider, too, fluoropolymer-based coatings. ETFE offers exceptional corrosion protection and permeation strength, and with many of the characteristics of epoxies.

For more information, see:
<a href="

http://www.industrialcoatingsworld.com/Corrosion-Resistant-Coatings/index.html">Corrosion

Resistant Coatings</a>

Good luck!





William Gunnar

http://www.IndustrialCoatingsWorld.com

 

[bao2ye]

Hello, Coatingengineer. Thank you so much for your great info.

 

[rodneybennet]

Hi Bao2ye:

You may also want to take a look at the discussion forum for simulation of chemical-physical properties of polymers and composite materials:

http://www.composite-agency.com/materials-forum.htm

On this forum you will find several cases similar to yours.

Regards,
Rodney

 

[bao2ye]

Thank you so much Rodney.

Yours is a good link. I like it.

 

[texasvalve]

For this application you might alos consider the BFVs with Nylon coated disc. They ususally hold up ptetty well over epoxy. Bray, Sure Seal, and Tyco make these types.