Formation of a Passive Oxide Film on Indium Electrode in Aqueous Solutions [ ]

The formation and growth of an oxide film on indium electrode immersed in sodium borate solutions has been followed and discussed using potential measurements under open-circuit conditions. The effect of concentration, pH and temperature of solution are also investigated. It is found that, the rate of oxide film growth follows a direct logarithm law, as evident from the linear relationship between the open-circuit potential and the logarithm of immersion time. The rate of oxide film growth decreases by increasing the pH of solution and by raising the solution temperature. The free activation energy of oxide film growth is determined and found to be 8.88kJ/mole, indicating that the process of oxide film growth is under diffusion control.