Enhancing understanding of cooperation mechanism of electrolyte composition on PEO coating growth for magnesium alloys via load characteristics

Abstract

To enhance the understanding of the cooperation mechanism of electrolyte composition on plasma electrolyte oxidation (PEO) coating growth, a new method via load characteristics was adopted. Based on the equivalent circuit and circuit components obtained from the voltage and current waveforms with time-domain reflection characteristics, the step-by-step PEO process and coating growth at each stage during a pulse period were discussed. The results show that in three different electrolytes, the loads exhibited second-order LCR oscillation attenuation characteristics. Before the electric spark breakdown more ions would gather at both ends of coating No. 2 because of the largest capacitance C. However, the phenomenon that the order of the three coating thicknesses was inconsistent with that of U_D indicates that the occurrence of breakdown mainly depended on the micro capacitors C_m, So sample No. 1 with the smallest U_D had the lowest breakdown voltage. During the coating growth the ion migration speed and heat output were closely related to R_a because the values of R_a were markedly greater than that of R₀. Thus, changing the load elements C, D, and R_a, exerted a synergistic effect on coating growth and growth models at each stage within a pulse period were proposed.