Preventing adhesion of epdm seal to brass, steel

[btrueblood]

We are using a peroxide-cured epdm diaphragm, and spraying it with silicone oil before installation. After a few hundred hours at 200 deg. F in water or water/glycol, the epdm becomes tightly adhered (stuck) to brass and/or steel surfaces.

Anybody have suggestions to prevent this adhesion?

Thanks,

Ben Trueblood

 

[SOLIDMODEL1]

Hi Ben,

Before the advent of bond paints, metal parts were brassed (layer of brass on the steel substrate) to get the rubber to adhere (albeit at higher temps), so preventing the diaphragm from sticking to the brass component may be difficult. As for sticking to the steel surface, there's some sort of reaction going on in the environment your describing.

Maybe coating the steel may help. Probably zinc plating.
It looks like you've got some experiments to do.

Conrad.

 

[btrueblood]

Conrad,

Thanks, yeah I knew about brass sticking, but typically this was done with sulfur-cured EPDM, and the sulfur reaction with brass (zinc?) would cause a chemical reaction to occur (dendrites of metal sulfides would penetrate into the epdm, or vise versa, can't remember the exact scenario). Was wondering if there is some other reaction that can occur between epdm and metals?

Ben T

 

[garrity]

I'm new here so my reply may be too late to be helpful.

I wonder if any of the mold releases in the marketplace might work, or some way of incorporaing teflon between the EPDM and the metal. I'd try looking on Google using the search term "mold release" and distinguish between sprays and more extensive cavity treatments.

 

[btrueblood]

Thanks Garrity, it's never too late!

Yeah, I've tried putting various commercially available mold release compounds (sprays) onto the surface. Most of them seem to wash away over time, heavy silicone oil spray has been our best performer to date.

Teflon coated steel parts would probably work, and are the next step. We'll probably use one of the Whitford coatings.