Tuning Corrosion Properties of the Bio-Inspired AZ-Series Mg Alloys Using Electrochemical Surface Treatment under Varying Experimental Regimes

Abstract

Plasma electrolytic oxidation (PEO) is a preferable process applied to optimize the corrosion and wear properties of metals and their alloys, particularly magnesium (Mg) alloys used in highly demanded medical and aerospace applications. In this project, AZ series alloys (AZ31, AZ61, AZ91), which are the major commercial magnesium alloys, were coated using the PEO process under varying experimental conditions involving electrolyte with Si based ionic chemical networks together with hydroxyl and fluoride functionalities. Surface analysis was carried out using scanning electron microscopy (SEM). Data were further simulated and analyzed using imageJ software. SEM results showed that, increasing the concentration of Al as in AZ91 and AZ61, dendrites-dominated the microstructure at shorter processing times; a cratered-dendritic matrix was obtained at longer processing time. From the composition analysis, fluoride complex peaks were obtained for the higher Al-content alloy (AZ91), due to the localized intensive discharges made regular by the stable β-phases within the Mg matrix. Corrosion analysis was carried out using potentiodynamic polarization. The compact structure, higher growth rate, and stable chemical phases of MgF2 contributed to the highest hardness values ~1271.2 HV and corrosion potential ~−0.18 V for the AZ91 alloy.

A Nano-CeO2/Zn–Mn Composite Conversion Coatings on AZ91D Magnesium Alloy Surface of Corrosion Resistance Research

“…It further shows that the corrosion resistance is e hanced by blocking the entry of corrosive media. electric double layer at the reaction interface [41]. The larger the fitting resistance, the be ter the corrosion resistance, which is consistent with the results obtained by the polariz tion curve.…”

“…Due to the rough surface and uneven electrochemical performance of magnesium alloy conversion coating, phase angle elements are often used instead of capacitors to explain the behavior of high-frequency capacitive arcs. CPE1 and CPE2, respectively, represent the phase angle elements of the corrosion products and the electric double layer at the reaction interface [41]. The larger the fitting resistance, the better the corrosion resistance, which is consistent with the results obtained by the polarization curve.…”

Research on the Corrosion Resistance of an Epoxy Resin-Based Self-Healing Propylene Glycol-Loaded Ethyl Cellulose Microcapsule Coating

“…Therefore, in this context, the poor corrosion resistance of magnesium alloy itself restricts the development of magnesium alloys. This situation urgently needs to be addressed [11][12][13][14]. The surface of magnesium alloys is similar to that of aluminum alloys; it also has a layer of magnesium oxide coating.…”