Corrosion Properties of New Magnesium Alloys

Magnesium alloys are being used in a broad variety of structural applications in the automotive, aerospace, electronics, and consumer products industries. While the growth of these applications has been driven primarily by weight savings, other advantages of magnesium alloys have played an important role. A major advantage is their unique suitability to the die casting process, allowing high rate production of near-net shape parts. Along with superior die life, this yields production cost savings that can more than offset the raw material cost advantage of competitive die cast aluminum alloys. Excellent machinability and superior damping properties are other important properties of these alloys.

An outstanding feature of the new generation of magnesium alloys is their superior resistance to salt water corrosion. Originally developed in AZ91D, this property has been extended to alloys of lower aluminum content which offer specific advantages such as greater ductility and impact strength, higher damping, or improved creep strength. The corrosion behavior of these alloys is reviewed. The particular problem of galvanic compatibility of magnesium, especially with ferrous metal fasteners, is discussed and approaches to the solution are evaluated.