Corrosion behaviors of Mg-39Pb-11.5Al-1B-0.4Sc alloy in 3.5 wt.% NaX (X=F, Cl, Br and I) solutions
(Faculty of Materials Science and Engineering, Kunming University of Science and Technology, Kunming 650093, China)
Abstract: Mg-39Pb-11.5Al-1B-0.4Sc alloy was prepared by melting method, and the corrosion behaviors and mechanisms in 3.5 wt.% NaX (X = F, Cl, Br, and I) solutions were analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), polarization curve test, and electrochemical impedance spectroscopy (EIS). The results show that the phases of Mg-39Pb-11.5Al-1B alloy are α-Mg, Mg2Pb, Mg17Al12 and AlB2. The addition of Sc can refine the microstructure significantly. The corrosion resistance of Mg-39Pb-11.5Al-1B-0.4Sc alloy in NaX solutions is in the order of NaCl < NaBr < NaI < NaF. During the corrosion process in NaX (X=Cl, Br, and I) solutions, Mg is first dissolved, then Mg2Pb is dissolved, and finally Mg17Al12 is fallen off from matrix. The corrosion products of Mg and Mg2Pb are Mg(OH)2 and MgO, respectively.
Key words: Mg-39Pb-11.5Al-1B-0.4Sc alloy; halogen solutions; polarization curve; electrochemical impedance spectroscopy (EIS); microstructure; corrosion performance