Red rot (brass)

Red rot is a term commonly used to refer to any reddish patch of corrosion on a copper-based alloy, such as brass. However, this loose usage covers two distinct but related conditions, surface corrosion and deterioration of the alloy due to de-zincification.

De-zincification results from the chemical reaction of acidic compounds left from the breath of the musician. Carbon dioxide is a natural part of human breath and when it comes in contact with water it forms carbonic acid. Drinking carbonated beverages such as sodas can increase the level of the acid inside the instrument. Also some metal cleaning compounds have acid in them and can attack the zinc in the brass. Also, moisture left inside the instrument can encourage the growth of bacteria that produce acids. The effect can be minor and only cosmetic or it can become severe enough that the metal actually leaks air through sponge like holes. Eventually the copper becomes so soft that it can be crushed with very little effort. Cleaning the instrument after each use can usually keep red rot from ever affecting the instrument. [ [http://www.brassarts.com/about_red_rot.htm About Red Rot ] ]

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