PEO on Mg AZ31 with Sepiolite as Inhibitor Carrier for Improved Corrosion Protection

What is it about?

Plasma electrolytic oxidation (PEO) in an alkaline silicate electrolyte containing nanosized sepiolite fibers was carried out on magnesium alloy AZ31. The mineral fibers were loaded with different corrosion inhibitors and incorporated in situ during the PEO treatment. The composition and microstructure of the PEO coatings were investigated by SEM. It was shown that the fibers are located on the surface as well as inside the “weak spots” of the coating, i.e., pores and discharge channels. The fixation of the particles is caused by sintering due to the heat developed during the PEO treatment. Investigations using electrochemical impedance spectroscopy and linear sweep voltammetry in 0.01 M NaCl solution confirmed an improvement of the corrosion protection. The use of the inhibitors shifts the critical pitting potential in the anodic direction. Regarding efficiency, cerium-loaded sepiolite showed the best behavior by shifting the pitting potential by +0.9 V.

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Photo by Naoki Suzuki on Unsplash

Photo by Naoki Suzuki on Unsplash

Why is it important?

Plasma discharges in the PEO process lead generally to the formation of craters in the resulting oxide layers. Thus it is of interest to increase the corrosion resistance inside these craters by incorporating suitable corrosion inhibitors.

Perspectives