The actual potential distributions inside cavities under gas evolution and film formation conditions

The non-uniform distribution of the electrode potential within submerged cavities is an important consideration in understanding the mechanisms of various electrochemical processes. In the present paper, the actual potential distributions inside cavities have been measured under conditions of gas evolving and oxide film formation on titanium electrodes in neutral media using scanning micro-reference electrode technique. The experimental results show that the bubbles motion and films growth inside cavities which differ greatly from that on flat or vertical electrodes, exert substantial effects on the potential distribution characteristic. The anomalous high-amplitude of potential variation and the unexpected local potential increase in the bottom part of cavities caused by the coalescing bubble covering cavities has been experimentally revealed. Moreover, under oxide film formation, once the completed oxide film is generated, the potential and current will be redistributed inside cavities. By improving the upper surface coarseness, a uniform potential distribution inside cavities can be achieved. The non-uniform distribution of the electrode potential within submerged cavities is an important consideration in understanding the mechanisms of various electrochemical processes.