Transient voltage-current characteristics: New insights into plasma electrolytic oxidation process of aluminium alloy

In order to clarify the electrochemical mechanism of plasma electrolytic oxidation (PEO), SEM, Mott-Schottky measurement, and the transient voltage and current (V-I) characteristics were utilized to systematically investigate conductive properties and reaction process of aluminium electrodes. Results indicated that the aluminium electrode coated with oxide coatings exhibited n-type semi-conducive properties and it had a Schottky barrier diode (SBD)-typed structure with the rectification effect on current. These made the transient I-V characteristics have different behaviors in loading and unloading branch of the anodic region during PEO process of aluminium alloy electrode. Moreover, in-situ monitoring on the whole PEO process discovered that the resistance of PEO coatings in anodic and cathodic directions were both increased as treatment time prolonged. These methods and results reported in this paper would offer some new insights into the mechanism of PEO technique.