Problems with epoxy baffles?

[Dr G]

Has anyone else experienced a problem with epoxy baffles peeling away from a brass m'piece? It makes since to me that it could/should happen eventually. I've already seen it on several modified Links.

I can imagine at least two scenarios/reasons for this failure. The first might be an issue of differing coefficients of thermal expansion. The second possibility is that of an oxide developing at the epoxy/brass interface and degrading the adhesive bond. Since the oxide has little tensile strength, the residual stress in the epoxy just pulls it away from the brass.

I've seen the failure occur in two different regions - at the sidewalls (beneath the rail edges) and at the base of the baffle (away from the tip). I'm considering wicking cyanacrylate glue into the voids as a shortterm fix but it doesn't speak well for longterm stablility.

[mark_m]

Thermal expansion would be the big cause, I'd think. The presence of the epoxy will minimize the likelihood of oxidation under it, until thermal expansion differences pull the two materials away from each other.

I'd be careful about cyanoacrylate, I think it's fairly toxic isn't it? Might want to check that out before having it on your mouthpiece...

[Dr G]

Thermal expansion would be the big cause, I'd think. The presence of the epoxy will minimize the likelihood of oxidation under it, until thermal expansion differences pull the two materials away from each other.

I'd be careful about cyanoacrylate, I think it's fairly toxic isn't it? Might want to check that out before having it on your mouthpiece...

The epoxy may protect against the entry of gross contaminates but I doubt that it is a diffusion barrier. There are exists the problem of how the surface is prepared before the epoxy is added and whether the catalytic reaction of the epoxy itself may do something to the surface.

Cyanacrylate adhesives are used in surgical procedures instead of stiches in some instances. I would regard it as having only minor toxicity and that only when it is in the liquid state.

[BATMAN]

Theo Wanne uses an epoxy/brass mixture for his baffles, and they seem to last a long time. I haven't seen or heard of one that has peeled away as of yet.

[mark_m]

Maybe just a matter, then, of good surface preparation in the first place to get a perfect bond between the metal and the epoxy.

[Dr G]

... and maybe not unless you are tacitly implying that the surface preparation includes applying a passivating diffusion barrier.

[mark_m]

A what?