Modes of inhibiting electrode processes (corrosion included) and their experimental discrimination II. Methodology for the investigation of the different modes of inhibition

In the field of inhibiting electrode reactions three methodological aims are to be underlined: 1. to identify inhibition and its modes, 2. to determine the effects of inhibition and 3. to investigate the causes of inhibition. This work is involving one of the tasks of the Working Party “Inhibitors” of the European Federation of Corrosion. Physical, chemical and electrochemical methods are used or proposed for these three tasks regarding the interface‐inhibition. For these both modes of inhibition, primary and secondary inhibition are to be distinguished. In the case of electro‐lyte‐layer inhibition, separation of the species mechanical and electrochemical electrolyte layer inhibition is necessary. As examples of inhibition in applied electrochemistry corrosion inhibition and inhibition in electrocrystallization of metals are treated. As to corrosion inhibition, ultimately, all investigation methods are to be related to the electrode reaction taking place without external electrical field, i.e. at the corrosion potential and the corrosion current density. In corrosion protection, investigation methods should examine especially the completeness of interface‐inhibition, membrane inhibition, passivation and the cooperation of electrolyte‐layer inhibition. On the other hand, for inhibition of the electrocrystallization of metals, the degree of coverage obtained by membrane inhibition or passivation would be too high. The investigation methods must be adapted to a moderate interface inhibition only at certain active sites of the surface. Highly sensitive morphological inhibition which has to be studied by special methods is belonging to the peculiarities of the inhibition in electrocrystallization.