EFFECT OF VELOCITY ON THE OPEN CIRCUIT POTENTIAL AND CORROSION RATE OF ALUMINIUM ALLOYS.

A study of the effect of velocity on the corrosion of aluminium and its alloys has been made. In particular, an overview of the effect of seawater velocity on the recently developed aluminium alloys has been presented. The rate of corrosion of aluminium and its alloys is higher under dynamic conditions of flow as compared to static conditions. The effect of velocity is dependent on the stability of the oxide film and the transfer rate of OH** minus . It has been observed that under dynamic conditions of flow the open circuit potential of the modified alloys is shifted to less negative values. Surprisingly enough, modified alloy 2778-H remains virtually unaffected by increase of velocity, which reflects its excellent resistance to corrosion by velocity. Although the mass transfer phenomena at electrodes has been extensively studied, its effect on the pitting potential and mechanism of pitting is not clearly understood.