Electrodissolution of Ti and p-Si in acidic fluoride media: formation ratio of oxide layers from electrochemical impedance spectroscopy

The electrodissolution of Ti and p-Si electrodes in acidic fluoride solutio ns has been investigated by electrochemical impedance spectroscopy as a fun ction of potential E, fluoride concentration, pH and angular speed of the e lectrode, with the aim of characterising the oxide layers covering both mat erials. The impedance diagrams have been analysed to obtain the low frequen cy capacitance C-lf the high frequency capacitance C-hf and the product Rhf I (where R-hf is the high frequency resistance and I the steady-state curre nt). In the potential domain where the oxide thickness x is proportional to E, the formation ratio dx/dE has been computed from C-lf, C-hf and RhfI. T he calculated values have been found to be in good mutual agreement and clo se to the ones found in the literature. (C) 2000 Elsevier Science S.A. All rights reserved.