Effect of the nitrogen inducing agents on the corrosion behavior of the oxide coatings prepared by electrolytic plasma processing on the Al2021 alloy

The AlON–Al2O3 oxide coatings were prepared on the Al2021 alloy by the electrolytic plasma processing (EPP) method at room temperature in 15 min under a hybrid voltage with various nitrogen inducing agents. The nitrogen inducing effects were studied by X-ray diffractometer (XRD), scanning electron microscopy (SEM). The corrosion behavior was evaluated by electrochemical tests in a 3.5 wt% NaCl solution under static conditions by open circuit potential and potentiodynamic polarization. The results show that NaNO2 is a suitable steady nitrogen inducing agent to prepare a uniform and dense AlON–Al2O3 coating on the Al2021 alloy to protect the substrate corrosion.