tarnish
/ˈtɑɹnɪʃ/
noun
Meaning
Oxidation or discoloration, especially of a decorative metal exposed to air.
verb
Meaning
To oxidize or discolor due to oxidation.
"Careful storage of silver will prevent it from tarnishing."
To soil, sully, damage or compromise
"He is afraid that he will tarnish his reputation if he disagrees."
To lose its lustre or attraction; to become dull.