Somehow we managed to deposit what seems like products of vaporization of a chemraz (fluoropolymer) seal, on gold plated precision mirror of an optical instrument (FTIR analyzer). It is a wonderful material in terms that it is inert to most known chemicals, even at high temperatures, unfortunately, this is to our disadvantage.
Is there a chemical (or thermal?) process to remove the deposits, without affecting the geometry of the mirror by scratches? The mirror is made from what looks like a nickel alloy, coated with a thin layer of gold. We can recoat with gold if needed, we would like to avoid having to resurface the mirror.
It might be rather difficult to remove such kind of contamination ― if indeed due to a cured perfluoroelastomeric (FFKM)* material ― by means of using a solvent or solvent mixture. Chemical resistance of such materials to solvents, although generally excellent, varies noticeably with exact type. Nonetheless, it might be worth to try some amine solvent, such as: benzylamine, cyclohexylamine, diamylamine, dicyclohexylamine, diethylamine, or diethylenetriamine. Moreover; also acetaldehyde, acrylic acid, amyl acetate, butyl acetate, dimethylbutadiene, isoprene, or formamide, could possibly help. Such solvents, preferably used hot or at their boiling point (under reflux), seem likely candidates to possibly succeed at extensively degrading crosslinks of the cured perfluoroelastomeric material. The degraded material, probably not dissolved, could perhaps be then dissolved with further help from some perfluorocarbon solvent (perfluorohexane, perfluorodecalin, etc.), which could perhaps also be used mixed with a miscible solvent selected from those indicated first. FFKM materials have considerable high-temperature resistance. Perfluorocarbon solvents are generically able to dissolve uncured perfluoroelastomers. FKM* fluoroelastomer materials are less chemical resistant.
* Accordingly ASTM D1418 Designation.
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