The alloy AA2214 is one of the medium to high-strength age-hardening forging alloys which play an important role as structural materials in the aircraft industry. For purposes of protection against corrosion and wear these alloys are very often anodized. Transmission electron microscopic studies on coatings anodized by sulfuric acid have clearly shown the effect of anodizing voltage on pore size. Intermetallic phases occurring in the microstructures of such materials were shown to be largely broken up during the anodizing process. Small proportions of alloy elements were, however, still detectable in the oxide. During the subsequent sealing process these open pores are closed and after only 15 minutes the process is substantially completed, revealing no significant gradation of density throughout the thickness of the oxide coating.