Current density effects on plasma emission during plasma electrolytic oxidation (PEO) on AZ91D-magnesium alloy

Abstract

The effect of bipolar pulse mode current ratio (anodic to cathodic) on plasma emission behavior was investigated in Plasma Electrolytic Oxidation (PEO) on AZ91D Mg-Alloy. Two cases of current ratio as 1.20 and 0.88 were applied to the sample. Plasma emission behavior was studied using plasma images and plasma emission measured by photodetector and Intensified Charged-Couple Device (ICCD) camera. The current ratio of greater than 1 shows the continuous increase and then stabilization in emission intensity with a gradual increase in voltage throughout the PEO process. In contrast, the current ratio of less than 1, a sudden drop in plasma emission intensity with voltage was found after 786 s. Therefore, PEO process can be divided into two regimes, arc regime and soft regime, before and after voltage drop, respectively. Results of measured spectra show that a soft regime does not have atomic or ionic excitation during PEO process. It is demonstrated that the growth of porous layer during PEO can be controlled, which is benefit for the protective oxide coating of sample.

Analysis of technological approaches to electrochemical surface treatment of aluminum alloys

“…Factors affecting the course of PEO processes are a set of technological parameters, among which the main ones are treatment current density, PEO time and process voltage. Their variation allows controlling the process of surface homogenization and formation of oxide layers [49]. The study of the mechanism of PEO treatment of aluminum alloys by analyzing the differential dependencies dU/dt-U ( Fig.…”