Review and theoretical analysis of ac–av methods for the investigation of hydrogen insertion: Part III. Comparison of entry side impedance, transfer function and transfer impedance methods

The alternating current–voltage methods proposed in the electrochemical literature to investigate hydrogen insertion and diffusion in metals and alloys are discussed and compared, based on the theoretical expressions for the entry side impedance, potential and current density transfer functions and transfer impedances. In particular, the conditions for the determination of the hydrogen concentration, the diffusion coefficient and the insertion rate constant from experimental data are analysed theoretically in relation to the electrode or membrane type and the electrical method considered.