Due to the high temperatures involved, the retort is usually made of heat resistant alloys that resist oxidation.
It resists oxidation by air and is not attacked by non-oxidizing acids.
For example the sulfur atom resists alkylation and oxidation.
The luster can still be visible if the film has resisted atmospheric oxidation and other weathering.
Phenyl groups tend to resist oxidation and reduction.
At standard temperature and pressures beryllium resists oxidation when exposed to oxygen.
Outdoor applications may require the jacket resist ultraviolet light, oxidation and rodent damage.
This gray material resists oxidation by air and is nonvolatile.
It reacts with chlorine to give mercuric chloride, which resists further oxidation.
They chose 24-karat gold because it not only resists oxidation but looks pretty, even under a microscope.