The aim of this work was to study the effect of gadolinium content on the corrosion behavior of magnesium alloys in 1 wt.% NaCl solution at 21.5 (±0.5) °C. Four Mg-Gd alloys, namely Mg-2 wt.% Gd, Mg-5 wt.% Gd, Mg-10 wt.% Gd, and Mg-15 wt.% Gd, were studied. Weight loss measurements, potentiodynamic tests, electrochemical impedance spectroscopy, XR diffraction, and scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS) were performed on the four Mg-Gd samples. The results showed the influence of the Gd content on the corrosion behavior of these alloys in 1wt.% NaCl solution. The corrosion resistance of the Mg-Gd alloys was improved with the introduction of 10 wt.% Gd in Mg matrix. Thus, weight loss and electrochemical measurements revealed the better corrosion resistance for Mg-10 wt.% Gd alloy. Further addition of Gd exceeding 10 wt.% in a magnesium matrix reduces the corrosion resistance of Mg-alloy and induces an incremental increase in the corrosion rate.

Corrosion resistance of AZ31 magnesium alloy was evaluated in aqueous chloride-containing solutions. Combined weight loss and electrochemical data indicate that corrosion rate of magnesium alloy increased for greater NaCl concentrations and higher temperatures. Corrosion is characterized by the formation of precipitates, that present the distinctive XRD patterns corresponding to crystalline phases of Mg(OH) 2 , accompanied by H 2 evolution, these processes leading to pH increases in the solution. Retrieved samples show a film of corrosion products distributed around cracks on the bare metal surface, and the subsequent development of large pits that prevent the material from attaining passive protection.

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