In this work, KOH, Na2SiO3 and Na2B4O7 were used as electrolytes for pulsed DC micro-arc oxidation (MAO) process. We studied the effect of KOH concentration of these electrolytes on the microstructure, chemical composition, and electrochemical behavior of pulsed DC MAO coatings formed on AZ31B Mg alloy. The surface characteristics of the coatings have been investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). All electrochemical measurements revealed that pulsed DC MAO process significantly improved the electrochemical behavior of AZ31B Mg alloy. Moreover, these measurements revealed that the sample 3 (1.5 M KOH) exhibited the best electrochemical behavior which resulted in high corrosion resistance compared to that of the other MAO treated samples. This behavior is attributed directly to the pore size, porosity percentage and micro-cracks. According to SEM micrographs, with increasing KOH concentration from 0.5 M to 1.5 M, the average pore size and porosity percentage decrease. However, increasing the concentration from 1.5 M to 2.0 M causes deleterious influence on the average pore size and micro-cracks.
