Corrosion behavior of Mg–2.4Zn alloy micro-alloyed with Ag and Ca

• Corrosion of four new cast Mg–Zn alloys in NaCl solution is carried out.
• Effect of alloying addition (Ag, Ca, Ag + Ca) and ageing on corrosion is studied.
• Size and distribution of precipitates play major role in corrosion.
• Ca-containing alloys show good corrosion resistance.
• Carbonate layer imparts good corrosion resistance to ZX60 and ZQX600 alloy.

The corrosion behavior of few cast Mg–Zn alloys, micro-alloyed with Ag and/or Ca (0.1 at.% each), has been investigated in 3.5 wt.% NaCl solution with the help of dynamic polarization, electrochemical impedance spectroscopy, and immersion tests. The effect of microstructures on corrosion behavior has been discussed thoroughly. The corrosion products formed on the immersed samples have been characterized by X-ray diffraction and Fourier transformed infrared spectroscopy. It has been observed that the Ca containing alloys show good corrosion resistance. This is attributed to the particular microstructure and carbonate-based protective film (corrosion products) formed on the surface.