ELECTROCHEMICAL-BEHAVIOR OF VANADIUM IN AQUEOUS-SOLUTIONS OF DIFFERENT PH

The electrochemical behaviour of vanadium in aqueous solutions of pH c overing the range 1-13 in oxygen saturated, oxygen free and naturally aerated solutions was investigated. The behaviour of the vanadium elec trode 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 c hanges from -0.039 V/decade for solution of pH less than or equal to 8 to -0.058 V/decade for solutions of pH > 8. EIS investigations have s hown that the metal undergoes active dissolution in aqueous solutions. In solutions of pH > 8 the corrosion behaviour of vanadium can be sim ulated to a Randles equivalent circuit model. In oxygen saturated solu tions the electrode surface is covered with an oxide film. The interac tion of this film with the H+ and OH- in solutions with different pH w as discussed. Polarization measurements have shown that the rate of co rrosion in acid solutions is not affected by the prevailing gas. In al kaline solutions, removal of oxygen or air from the solution leads to a decrease in the corrosion rate of the metal. Copyright (C) 1996 Else vier Science Ltd