EFFECT OF EXCESS NEGATIVE IONS ON ANODIC OXIDATION IN MICROARC OXIDATION

The effects of the electrical bias conditions on oxide film during titanium MAO (microarc oxidation) were investigated. Since DC voltage showed very low stabilized currents but produced oxide films with poor quality, the magnitude of applied voltages, duty cycles, and frequencies were modulated to control the quality of the oxide film. Pulsed voltage showed increased stabilized currents but produced better oxide films. The change in the stabilized currents was attributed to the change of the resistances of the film and local electrolyte adjacent to the anode. Analysis of the film thickness and the resistances of the film calculated from the experiments led to conclusion that the resistance of the electrolyte adjacent to the anode was increased if the negative ions attracted towards the electrical bias condition depended on the experimental configuration.