Corrosion Protection of Magnesium Alloys

Special care must be given to the fabrication of magnesium joints due to the high susceptibility of this metal. When joining two magnesium parts, a chemical conversion coating should be used, followed by one or more primer coats having alkali resistance such as an epoxy or vinyl resin. Fasteners for Mg-Mg joints include 5056 Al rivets, 6061 Al bolts, and cadmium or zinc plated steel bolts. For joining magnesium with a dissimilar metal, the surfaces must be insulated with an organic tape, sealing compound, or an alkali resistant paint. The joint should be fastened with cadmium plated steel bolts and nuts with a 5052 aluminum washer separating the steel and magnesium. Only 5056, 6061, and 6053 aluminum alloy bolts and screws can be used bare, to join magnesium. All other metal fasteners should be coated when used with magnesium. Some general procedures to limit corrosion in magnesium structures are listed in Table 40.