An investigation of plasma electrolytic oxidation coatings on crevice surface of AZ31 magnesium alloy

Abstract In an attempt to investigate the formation rule and corrosion resistance of the plasma electrolytic oxidation (PEO) coating on crevice surface of AZ31 magnesium alloy, the crevice coatings were fabricated on the samples of irregular shapes with different values of crevice width. The value of crevice width was varied from 200 to 350 μm for investigating the effect of crevice width on the surface and cross-sectional morphology, phase composition, corrosion resistance of crevice coatings. The results indicated that the crevice coating differs markedly in morphology and corrosion resistance when the value of crevice width reaches 350 μm, in spite of all coated samples have similar phase compositions. The effect of current density and ultrasound treatment on crevice coatings thickness were also studied systematically. Studies have shown that the increase of current density and the introduction of ultrasound treatment are both favorable for the crevice coatings.