Magnesium Corrosion Protection by Design

Magnesium alloys are attractive for applications in aerospace because of their low density.  However, there are some key barriers that need to be overcome to expand the use of Mg in aerospace, especially in commercial airplane.  Surface protection is one of the keys.  The main purpose of this study was to assess the corrosion behavior of extruded WE43-T5 for aerospace applications.  General corrosion, evaluation of current corrosion protection systems, coating durability, and galvanic corrosion were addressed.  It was identified the most critical technical consideration was galvanic corrosion, to which the most significant portion of this effort was dedicated.

It has been clearly understood that galvanic corrosion is an inherent characteristic of any Mg alloys when coupled with a dissimilar alloy in the presence of an electrolyte.  With this understanding, galvanic corrosion can be mitigated by proper design and processing methods.  The important considerations included: 1) selection of the fasteners that are closest to Mg on the galvanic scale, 2) isolation and protection of magnesium and fastener components by coatings and paints, 3) prevention of wetting, and 4) minimization of galvanic zone.  Using this methodology, corrosion protection for Mg structures can be designed based on application requirements, ranging from minimal to robust.

A comprehensive view of corrosion protection has been developed for Mg alloys.  For many aerospace applications, robust magnesium corrosion mitigation can be provided by utilizing appropriate design and processing methodologies.