Chapter 29 Application of Plasma Electrolytic Oxidation to the Novel Aircraft Aluminum Alloy for Enhancing Corrosion Resistance

摘要

Plasma electrolytic oxidation (PEO) has been considered as a novel technique to form ceramic coatings on aluminum alloys for corrosion protection. The effect of PEO on the intergranular corrosion (IGC) behavior of the novel high-strength aluminum alloy 7A85 was investigated. Electrochemical polarization technology was used to study the influence of PEO on the electrochemical corrosion behavior of AA 7A85. The IGC mechanisms of PEO and PEO combined with sealing-treated AA 7A85 were studied by metallographic analysis, XRD analysis, and scanning electron microscopy. The results show that AA 7A85-T7452 is very sensitive to IGC. PEO would reduce the largest corrosion depth by 41.6 %. PEO without sealing did not eliminate the IGC for the micropores and microcracks in the oxide coating. However, PEO combined the SiO_2 sol gel sealing treatment could effectively protect the AA 7A85-T7452 from IGC for the good corrosion resistance and barrier function of the sealed coating.