A potentiostat is an electronic instrument which maintains a constant electrode potential of a preset value with respect to a reference electrode. If the signal attempts to drift from this value, the error signal is amplified and is fed into the output stage which provides a change in current passing through the circuit to correct this error. Potentiostatic techniques have been used for a variety of applications: organic oxidations and reductions,1-3 controlled electroetching of metal,4,5 corrosion studies,6-10 analytical chemistry.11,12 Their most popular use is with systems that show active dissolution and passivity at different potentials.
Corrosion processes can be generally explained on the basis of the electrochemical reactions taking place at the metal/solution interface. The electron-transfer processes involved in the corrosion of iron can be presented diagrammatically as the following reactions:
