MECHANISM OF INDIUM ELECTRODEPOSITION ON BISMUTH CATHODES AND TIME EVOLUTION OF THE DEPOSITS

The mechanism of the indium electrodeposition process from aqueous sol utions on bismuth cathodes has been investigated as well as the evolut ion with time of the composition of the deposits after electrodepositi on. The potentiometric results and the changes in composition and stru cture are explained by considering the transport phenomena and the rea ctions occurring in the solid state owing to indium diffusion into the electrode and to the formation, generally, of the multiphase layer In -In2Bi-In5Bi3-InBi. Such analysis allows estimation of the room temper ature average diffusion coefficient of indium in the three intermetall ic compounds (ca. 10(-15)-10(-16) m(2) s(-1)). Moreover, consideration of the indium chemical potentials within each compound makes it possi ble to account for the evolution of the system with time to InBi.