Magnesium and Its Alloys

Magnesium has the lowest density of the metals but it also has the highest susceptibility to corrosion effectively eliminating it from use in most applications. An oxide layer will form on magnesium; however the thin film layers that form are usually soluble in water and readily breakdown in the presence of ions such as chloride and bromide. Increasing temperatures will also accelerate degradation of the protective film leading to widespread corrosion of magnesium. Galvanic corrosion of magnesium is always a consideration since it is anodic to most metals. Coatings should always be used to protect magnesium alloys in structural applications. Use of Mg alloys in moving components has led to rapid breakdown of the coating system leading to corrosion of the unprotected Mg alloy material. Therefore, magnesium alloys are almost entirely used in non-moving structural applications with proper protective methods.