I did a simple Oddy test of Plasti Dip several years ago and it did
cause corrosion of several metals, although I imagine that much of the
problem was the curing process. I did not artificially age the resulting
material and then repeat the Oddy test. However, like with most
commercial products, I would be inclined to stay away from it.

Likewise, in terms of silicone please realize that not all silicones are
created equal -- some have rather significant off-gassing issues.

As an alternative: why not create your support using stainless steel
(tig rod comes to mind) and then seal it with one of several benign
forms of plastic tubing (such as teflon).

You might also want to take a look at some of the suggestions in the
excellent CCI publication, Mount-Making for Museum Objects.

Best,

Michael Trinkley, Ph.D.
Director
Chicora Foundation, Inc.
PO Box 8664
Columbia, SC  29202
803/787-6910
Email: [log in to unmask]