The magnesium alloy, EV31 has achieved wide acceptance in the aerospace industry since its introduction in 2005 due to its excellent mechanical properties and low corrosion rate.  Cold chill billet EV31 is growing in popularity in the manufacture of smaller aerospace parts as OEMs find it is easier to hog out billet than the extended time lines for sand cast material.  There appears to be a difference in the grain structure of cold chill billet EV31 vs. sand cast EV31.   The anodized coating – Tagnite has been shown to give the best protection of magnesium, however the characteristics of the Tagnite coating on cold chill billet EV31 has not been thoroughly investigated.

This paper will explain the metallurgical differences between sand cast and cold chill billet EV31 alloys.  In addition, the performance of these two materials after being coated with Tagnite and Brush Tagnite will be presented.  The anodized coatings structure and composition will be examined by SEM-EDX and the corrosion resistance, abrasion resistance, Rockhard paint adhesion, and electrical impedance characteristics of the coatings will be discussed.