Tarnish
Tarnish was the result of an oxidation chemical reaction that caused to certain metals to corrode.

Worf commented to B'Etor in 2370, that "You cannot tarnish a rusted blade," after she claimed that the would be assassins of Worf implicated them in order to "tarnish our good name." ()

According to Grand Nagus Zek's 2371 revised Rules of Acquisition #24: "Latinum tarnishes, but family is forever." ()

Rule of Acquisition #263 stated: "Never allow doubt to tarnish your lust for latinum." ()

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Chemical compounds