Corrosion behaviour and mechanical properties of Ag-20Mg alloy in chloride environments: an electrochemical and surface analysis study

Silver–magnesium (Ag–Mg) alloys are promising for lightweight structural and electronic components because they combine the functional properties of Ag with the low density and biocompatibility of Mg. However, the large electrochemical potential difference between Ag and Mg renders these alloys highly vulnerable to microgalvanic corrosion in chloride environments, necessitating a systematic evaluation of their degradation mechanisms. In this study, the corrosion behaviour of Ag–20Mg was investigated using potentiodynamic polarisation, electrochemical impedance spectroscopy (EIS), immersion testing, hardness measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). The alloy exhibited hardness values of 64–81 HV, a highly negative corrosion potential (Ecorr ≈ – 997.9 mV vs SCE), elevated corrosion current density (Icorr ≈ 902.8 µA), and a corrosion rate of 1211.9 mpy, while EIS revealed limited charge-transfer resistance (Rct ≈ 350–400 Ω·cm²). Immersion tests recorded a 0.34 g weight loss in 120 h, and surface analysis identified Mg(OH)2 rich porous films, chloride incorporation, and localised pitting driven by Ag–Mg galvanic interactions. The novelty of this study lies in the establishment of an integrated structure–property–corrosion framework for Ag–Mg alloys by linking the effects of the Ag distribution with the electrochemical response.