COMPUTER-ASSISTED ELECTROCHEMICAL MEASUREMENTS OF THE DIFFUSIVITY AND SOLUBILITY OF HYDROGEN IN METALS

Two methods are discussed in respect of their capability to characterize the hydrogen - metal interaction, namely the galvanostatic transient permeation method and the potentiostatic transient extraction method. In both cases explicit mathematic relationships between the controlled parameters and the measured response are available. These relationships are based on long-time solutions of the diffusion equations. A system of algorithms has been developed in order to carry out the computer-assisted electrochemical measurements of the transport and equilibrium properties of hydrogen in a metal. The following parameters can be estimated simultaneously on the same sample: equilibrium H concentrations, equilibrium H pressure, Sieverts' constant, the apparent diffusion coefficient, the true diffusion coefficient, the trap concentration and the trapping constant. Experimental data on the solubility and diffusivity of hydrogen on a reference palladium sample are discussed within Oriani's two-state model. The overall result of computerassisted measurements is that it provided a good quality of the acquired and processed data with a minimum analysis time. © R. Oldenbourg Verlag, München 1990