Fig. 1 XRD patterns of the prepared alloys

Fig. 2 Optical microstructure of the prepared alloys

Fig. 3 SEM images for the microstructures of the prepared alloys

Fig. 4 Volume fraction of secondary phase formed in different alloys

Fig. 5 WDS elemental mapping distributions for different alloys. Red circles refer to MgCaGe phase, yellow arrows indicate MgxZnyCaz phase, while yellow circles refer to Zn segregation

Fig. 6 HRTEM images, SAED patterns, dark field scanning transmitted electron microscopy images and the corresponding EDS analysis of the main phase in a Mg0.5Zn0.2Ge, b Mg0.5Zn0.2Ge0.1Ca alloys

Fig. 7 a SKPFM results of representative Mg0.5Zn0.2Ge and Mg0.5Zn0.2Ge0.1Ca alloys, b SEM morphologies of marked regions for the prepared alloys before and after immersion in 0.9 wt% NaCl for 10 min

Fig. 8 EIS results of different alloys immersed in 0.9 wt% NaCl solution for 1 h and 24 h

Fig. 9 Variations of impedances at f = 0.5 Hz for different alloys during 48 h of immersion

Fig. 10 Potentiodynamic polarization curves of different alloys after 48 h of immersion in 0.9 wt% NaCl solution

Fig. 11 a Collected hydrogen volume for different alloys as a function of immersion time, b average corrosion rate calculated from collected hydrogen volume and mass loss after 168 h of immersion in 0.9 wt% NaCl solution

Fig. 12 XRD patterns for different alloys after 48 h of immersion in 0.9 wt% NaCl solution

Fig. 13 a SEM images of samples surface after immersion in 0.9% NaCl solution, b cross sections and elemental mapping results for different alloys