Unusual behavior of magnesium and ZM anodes in aqueous electrolytes at high concentrations

Potentiodynamic polarization was performed to understand the effect of rotation and concentration on the corrosion behavior of Mg and ZM alloys in sodium bromide (NaBr). sodium sulfate (Na₂SO₄), and magnesium sulfate (MgSO₄) solutions up to 2.0 M. The variation of corrosion potential and corrosion current with electrode rotation and concentration of the electrolytes was analyzed. Kinetically controlled current (i_x) calculated from the plot of inverse current (i^-1) us square root of rotation (w^-1/²) showed that the current was predominantly diffusion controlled in dilute solutions and low rotations, and a change to activation controlled occured at concentrated solutions and high rotations. The relationship between the hydrogen evolution rate (V_t) and concentration of the electrolytes as well as nature of the electrode materials also was investigated. Scanning electron microscopy (SEM) photographs showed that exfoliation and disintegration of the ZM anode was greater at high concentration and current density values, independent of the aqueous electrolytes used.