Tarnish
Tarnish is a thin layer of corrosion that forms over copper, brass, silver, aluminum, and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish; it does not tarnish with only oxygen. It often appears as a dull, gray or black film or coating over metal.
Causes[edit | edit source]
Tarnish is a product of a chemical reaction between a metal and a nonmetal compound, especially oxygen and sulfur dioxide. It is usually a metal oxide, the product of oxidation. Sometimes it is a metal sulfide. The metal oxide sometimes reacts with water to make the hydroxide; and carbon dioxide to make the carbonate.
Prevention[edit | edit source]
Tarnish can be prevented by storing metals in an oxygen-free environment. More commonly, tarnish can be prevented by coating the metal with a thin layer of oil or a clear lacquer.
Removal[edit | edit source]
Tarnish can be removed by using a solution of baking soda, or toothpaste, and a soft cloth. Using a paste made of baking soda and water is also effective. There are also commercial tarnish removers available.
See also[edit | edit source]
Tarnish Resources | ||
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