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Magnesium Corrosion

In some environments magnesium part can be severely damaged unless galvanic couples are avoided by proper design or surface protection. Unalloyed magnesium is not extensively used for structural purposes. Consequently, the corrosion resistance of magnesium alloys is of primary concern. A modern and comprehensive document on the subject is the second edition of the classic CORROSION BASICS textbook.

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Two major magnesium alloy systems are available to the designer.

A clean, unprotected magnesium alloy surface exposed to indoor or outdoor atmospheres free from salt spray will develop a gray film that protects the metal from corrosion while causing only negligible losses in mechanical properties. Chlorides, sulfates and foreign materials that hold moisture on the surface can promote corrosion and pitting of some alloys unless the metal is protected by properly applied coatings. The surface film that ordinarily forms on magnesium alloys exposed to the atmosphere gives limited protection from further attack.