tarnish

Oxidation or discoloration, especially of a decorative metal exposed to air.

1918, Hannah Teresa Rowley, Mrs. Helen Louise (Wales) Farrell, Principles of Chemistry Applied to the Household Precipitated calcium carbonate, a very fine powdery form, is used as a basis for many tooth powders and pastes. As whiting it finds a wide use in cleaning metals of their tarnishes.

Limiting the use of silver to special occasions might invite tarnish unless the pieces are carefully protected.

To oxidize or discolor due to oxidation.

Careful storage of silver will prevent it from tarnishing.

To compromise, damage, soil, or sully.

He is afraid that she will tarnish his reputation if he disagrees with her.

I have next shown you the Greeks, and " the wisdom" of their philosophy, often travesting, sometimes tarnishing the Christian religion : […]

To lose its lustre or attraction; to become dull.

Till thy freſh Glories, which now ſhine ſo bright, / Grow Stale and Tarniſh with our dayly ſight.

To use a sign, image, expression, etc. sufficiently close to a trademarked one that it brings disrepute to it.