How to remove silicone-potted inductor

[eldis111]

I'm trying to rescue an inductor out of an aluminium case. It is partially potted in grey silicone (or something very similar to it). It has rubbery feel to it, but bonds to the inductor and case very strongly.



Unfortunately the inductor is deep in the case, so there is no easy way to get in with a knife or tools. I know that there are some chemicals that can break down silicone to make it more brittle. The question is if they will not also damage the coating of the winding?

Thanks for any tips!

[ales22]

Usually the coating is very resistent to chemicals. It's not like some furniture varnish which you can wash off with a bit of thinner and it's quite a problem for soldering this "enamelled wires". I have special solder flux which attacks the coating, but only at high temperature. You may try some organic solvents like benzin or aceton, but if the case can be destroyed, I would use my Dremel (or BOSCH PWS 7-125) and carefully cut off the sides of that case. It looks quite big and solid, so it may be tedious work, because aluminium isn't the best metal for grinding.

[T3sl4co1l]

Concentrated nitric acid.*

*Warning: may dissolve the copper winding, and iron core, faster than doing anything at all to the potting.  Also, rather nasty.  Don't actually do this.

Resins can usually be swelled with a nasty solvent, like methylene chloride, but that disrupts or swells or dissolves a whole lot of kinds of plastics and resins and such.  So you might end up with clean wire... too clean.

It does matter if it's actually silicone, or epoxy, or urethane, or polyester, or... any of a number of other possible resins.  They've all got their flexible varieties, so it could be kind of anything just based on appearance.

Why do you need to "rescue" it out of there?  It looks quite happy where it is, and has a free heatsink besides!

Tim

[jwm_]

If it is urethane based like shoo goop or e6000, the toluene will take it right off.

[Kleinstein]

If you don't need the case anymore, you could dissolve die aluminium in something like NaOH solution. Just don't use to high a concentration (might get to hot) and good ventialtion (produces hydrogen gas).  The inductor should withstand NaOH.