Tarnish

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Tarnish is a layer of corrosion that develops over copper, brass, silver, aluminum as well as a degree of semi-reactive metals as they undergo oxidation. It is analogous to rust, but with a slower rate of occurrence.

Treatment

When tarnish occurs, it is treated chemically, usually with strong acids, which reacts with the oxide to yield a salt, which washes off. Many commercial products are dedicated specifically to this

Prevention

Most tarnishing is prevented by tinning, a process by which the reactive substance is coated in a non-reactive substance, such as tin or wax, and thus protected from oxygen.

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