Electrochemical behaviour of vanadium in aqueous solutions of different pH

Abstract

he electrochemical behaviour of vanadium in aqueous solutions of pH covering the range 1–13 in oxygen saturated, oxygen free and naturally aerated solutions was investigated. The behaviour of the vanadium electrode in alkaline solutions ( pH > 8) is different from that in acid or neutral solutions (pH 1–8). The equilibrium electrode potential is a linear function of the solution pH. The slope of the linear relation changes from −0.039 V/decade for solution of pH ≤ 8 to −0.058 V/decade for solutions of pH > 8. EIS investigations have shown that the metal undergoes active dissolution in aqueous solutions. In solutions of pH > 8 the corrosion behaviour of vanadium can be simulated to a Randles equivalent circuit model. In oxygen saturated solutions the electrode surface is covered with an oxide film. The interaction of this film with the H + and OH − in solutions with different pH was discussed. Polarization measurements have shown that the rate of corrosion in acid solutions is not affected by the prevailing gas. In alkaline solutions, removal of oxygen or air from the solution leads to a decrease in the corrosion rate of the metal.