Characteristics of electric parameters in aluminium alloy MAO coating process

Abstract

Characteristics of electric parameters in the microarc oxidation (MAO) process of aluminium alloy at constant voltage were studied by a homemade data collecting system. The experimental results show that (1) the variations of the cathodic and anodic current amplitudes and the effective working current reflect obviously five different stages in the course of treatment and (2) variations of the dynamic forward resistance and electric resistivity of coatings have different stages too, while changes of the dynamic backward resistance and resistivity with treatment time are not evident. During the MAO process, the dynamic forward resistance is not equal to the backward resistance at any time, and the former is generally greater than the latter. Scanning electron microscopy analysis shows that these changes are attributed to variations of the coating porous structure during different treating times.