Editors' Choice—Dealloying of MgZn2Intermetallic in Slightly Alkaline Chloride Electrolyte and Its Significance in Corrosion Resistance

The role of dealloying in the corrosion resistance of MgZn 2 has been investigated for the first time. The elemental dissolution kinetics of a synthetic, nominally pure MgZn 2 intermetallic compound was investigated and compared with pure Mg and Zn in 30 mM NaCl with pH = 10.1. Atomic emission spectroelectrochemistry was used to monitor Zn and Mg dissolution as a function of time at open circuit, during linear scan polarization, and at various applied potentials. Zn and Mg displayed a mutual inhibitive effect at open circuit which was explained by the formation of Mg depleted Zn / Zn oxide film. Polarization experiments revealed a Type II dealloying mechanism in which Zn and Mg dissolve simultaneously and congruently above the critical potential, E c , while preferential Mg dissolution dominates below E c . Preferential Mg dissolution leads to the formation of a Mg depleted metallic Zn layer which suppresses further Mg dissolution. In oxygen saturated electrolyte, O 2 reduction was the major cathodic reaction on Zn but was completely inhibited on Mg. The intense cathodic reduction of O 2 on Zn led to a cathodic dissolution of Zn, probably due to the increased interfacial pH.