Microstructure characteristics, film layer rupture mechanism and corrosion behavior of hot-rolled Mg-2Zn-0.2Mn-xNd

As yet, the selective-dissolution and abrupt hydrogen rate are still the main factors hindering the veritable service of the degradable Mg alloys. In the present study, the initial micro-areas dissolution and quiescent degradation mechanism of hot-rolled Mg-2Zn-0.2Mn-xNd in simulated body fluids were proven through atomic force microscope (AFM/SKPFM), transmission electron microscopy (TEM), confocal laser scanning microscopy (3D/CLSM), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectrum (FT-IR). The results revealed that the CaHPO4, Ca-10(PO4)(6)(OH)(2)/HA, MgO and Mg (OH)(2) deposited on the hot-rolled Mg-2Zn-0.2Mn surface, whilst the Mg(OH)(2), HA, Ca-3(PO4)(2), CaHPO4, MgCO3 and Nd2O3 deposited on hot-rolled Mg-2Zn-0.2Mn-xNd (0.62, 1.22, 1.88). The best corrosion resistance was obtained in Mg-2Zn-0.2Mn-0.62Nd, with the corrosion rate of 0.92 +/- 0.33 mm/y. The improvement of corrosion resistance was due to the synergistic effect of nobler Volta potentials, refined microstructure and compact layers on the Nd-modification Mg alloys, which reduced the galvanic intensity, facilitated the reaction rate of the film formation, concomitantly stabilized the film layer, resulting in lower dissolution rate of Mg matrix. Besides, the hydrolysis/ionization effect of Nd leaves the active sites for metal dissolution and offers Mg2+, Ca2+, HPO42- and OH- due to its hydroxide precipitation.