Corrosion resistance of modified magnesium-based alloys

The corrosion behavior of Mg95 magnesium alloy modified with Ti-Al-REM (REM = Sc, Y, Nd, Dy, Ho, Er, Zr, Hf) master alloys was investigated in a 3 wt.%NaCl solution using potentiodynamic linear polarization and electrochemical impedance spectroscopy (EIS).The results demonstrate that alloying with dysprosium (Dy) and holmium (Ho) significantly enhances corrosion resistance by reducing the corrosion current density (icorr) by approximately 35% compared to the base alloy.These modifications were also associated with increased polarization resistance (Rp) and higher low-frequency impedance values, indicating improved surface stability.In contrast, additions of yttrium (Y) and hafnium (Hf) were found to accelerate corrosion, increasing (icorr) by factors of 2.64 and 4.77, respectively.Microstructural analysis revealed that the beneficial effects of Dy and Ho are linked to grain refinement and the formation of stable intermetallic phases that promote the development of a protective oxide layer.This layer effectively suppresses cathodic processes such as hydrogen evolution, thereby enhancing the overall electrochemical stability of the alloy.On the contrary, Y-and Hf-containing alloys exhibited less uniform microstructures and weaker passivation abilities, leading to accelerated degradation.A strong correlation between microstructural changes and electrochemical performance was established, confirming that the corrosion protection mechanism is governed by both the formation of a stable oxide film and the inhibition of cathodic activity.The results indicate that incorporating dysprosium and holmium (Dy/Ho) holds considerable potential for improving the corrosion resistance of magnesium alloys in aggressive environments.