Micro-arc oxidation in various concentration of KOH and structural change by different cut off potential

The onset potentials of breakdown during titanium MAO (micro-arc oxidation) by several concentrations of KOH aqueous electrolyte were investigated in DC electrical waveform. As the concentration was diluted, the potentials increased. It might due to the higher electrolytic resistivity. The potentials are proportional to −log C where C is the concentration of KOH. This relation has good agreement with Ikonopisov’s electron avalanche model. Surface morphology was also investigated by different potential in 0.1 M KOH electrolyte. Just after breakdown, the surface has very tiny pores. As the potential increases, well-developed pores by discharges were observed. However, some overgrowth oxide was also observed for high potential. There may be appropriate potential to make homogeneous surface morphology for a given electrolyte condition.