Duty cycle influence on the corrosion behavior of coatings created by plasma electrolytic oxidation on AZ31B magnesium alloy in simulated body fluid

Abstract

Ceramic coatings were applied on the surface of AZ31 Mg alloy using plasma electrolytic oxidation procedure with distinct duty cycles (20%, 50%, and 80%) by a direct current mode in an alkaline electrolyte. The influence of the duty cycle on the corrosion performance of the coatings was studied in addition to their microstructures. In order to evaluate the corrosion performance of created coatings in different duty cycles, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements were measured in simulated body fluid (SBF). The surface properties and chemical compositions of the coatings were evaluated by X-ray diffraction pattern and scanning electron microscopy. The results indicated that in the higher duty cycles (80%), the created coating had a uniform surface with a lower porosity percentage and a higher thickness. The highest corrosion resistance arose from the least corrosion current density (6.46 ×10−6µA cm−2) of the produced coating in the higher duty cycles (80%).