Abstract
Electrochemical polarization experiments were made on the liquid and solid gallium electrodes in acidic sulfate solutions of pH 1.0∼3.0 over the temperature range of 288∼313 K. The cathodic polarization curves for hydrogen evolution on gallium exhibited a Tafel line with the slope of 0.12 V/decade in a limited range of current density. The exchange current densities were of the order of 10−5 A/m2 and their Arrehnius plots yielded a straight line which gave the apparent activation energy of 46.2 kJ/mol. No dramatic changes in the kinetics were observed at the melting point of gallium. The hydrogen evolution on gallium is probably controlled by charge transfer step. The anodic polarization curves on gallium were poorly dependent on the potential. It is likely that the anodic dissolution of gallium takes place via the formation of less-protective Ga2O3 film on the surface. Especially on a liquid gallium electrode, the anodic current increased steeply at −0.1 V (SCE), probably because of spalling of the anodic film.
The rate of corrosion of gallium in acidic sulfate solution was of the order of 0.3 A/m2 and increased with decreasing the pH value and increasing temperature. There were no specific changes in the corrosion rate above and below the melting point of gallium.
