| Popis: |
The oxide film formation and growth on indium electrode in Na2B4O7 solutions have been studied using polarization technique. The effects of concentration of Na2B4O7, pH and temperature of electrolyte solution are investigated based on the formation of oxide film. It was found that lowering the concentrations of Na2B4O7 solutions, pH or decreasing of temperature of the solution assist the formation of a passive oxide film on indium electrode. The corrosion current density, icorr, increased with increasing the concentrations of Na2B4O7 solutions, pH and the rising of solution temperature. The free activation energy of oxide film growth process is determined to be 15.7kJ/mole. The above studies indicate that the oxide film growth process is diffusion-controlled. The effect of addition of NaCl, NaBr, and NaI with different amounts was also investigated. Higher concentrations of these salts lead to the dissolution of the passive oxide film due to the increasing of corrosion current density, icorr, and the shift of corrosion potential, Ecorr, to more active potentials. |
