High-temperature interaction between gas and solid is normally treated as a diffusion problem in solid state science, using normal Fickian diffusion models. Metals and alloys owe their resistance to the action of oxidizing atmospheres at high temperatures to the scale which forms on their surface, if transport through this scale is the slowest step in the oxidation reaction. The morphology of sulfide scales is rather similar to that of oxide scales, which may be explained by analogous growth mechanisms, but there are differences. When an external potential difference is applied to the cell, the electronic current through the oxide is normally no longer equal to the ionic current: electrons can be produced at the electrodes. Cyclic voltammetry is a well-known technique in wet electrochemistry. It is mainly used to obtain an electrochemical spectrum of the system studied and to obtain information on the kinetics of the reactions.