Surface Properties and Corrosion Performance of NaOH Treated Mg Alloy in Simulated Body Fluid Solution

The influence of NaOH treatment on the surface properties and corrosion performance of AZ31 Magnesium alloy has been investigated. The treated alloys showed a uniform porous morphology, and a marginal difference was noticed with varying NaOH concentrations. The NaOH-treated AZ31 Mg alloy surfaces mainly consisted of magnesium hydroxide (Mg(OH) 2 ), and the X-ray diffraction (XRD) studies confirmed the existence of Mg(OH) 2 with a hexagonal crystal lattice structure. Potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and dynamic EIS (DEIS) studies in simulated body fluid (SBF) solution revealed that the corrosion resistance increased when the NaOH treatment concentration increased to 8 M; the further increase resulted in a decreasing trend. The corrosion current density (i corr ) of treated alloys was substantially decreased, particularly ~ 7 times decrease was achieved for the alloy treated with 8 M NaOH than untreated alloy. In addition, the EIS results revealed a higher surface layer and charge transfer resistance for the treated alloys. The corrosion rates from hydrogen evolution volume and weight loss methods after 120 h of immersion revealed a decrease in the corrosion rate of ~ 3 times for 8 M NaOH treated alloy than untreated alloy. After immersion in SBF solution, surface studies of treated alloys confirmed the deposition of Magnesium-doped calcium phosphate compounds with enhanced corrosion resistance and bioactivity. Graphical Abstract