Study of Sodium Aluminate Concentration Influence on the Corrosion Behavior of Plasma Electrolytic Oxidation (PEO) Coatings on 6061 Al Alloy

In this study, the surface of 6061 Al alloy sheets were treated by plasma electrolytic oxidation (PEO) process to obtain oxide coatings. The voltage-time curves shows that the breakdown potential decreases with increasing of electrolyte concentration. The effect of concentration of PEO electrolyte on the corrosion behavior of the coatings was investigated. To assess the corrosion behavior, the potentiodynamic polarization plots were achieved and electrochemical impedance spectroscopy (EIS) measurements were carried out. The results of these analyses indicated that by reducing the concentration of sodium aluminate in the electrolyte, the corrosion rate of the coatings on the 6061 Al alloy significantly decreased. Moreover, the variation of sodium aluminate concentration in the electrolyte, led to modification of morphology and micro porosity of the coatings and alteration of the responses in the voltage-time. The coating processed in the electrolyte which contained 10 g L-1 sodium aluminate exhibited the best corrosion resistance.