Measurement of corrosion rate using two electrodes

Instruments to measure corrosion rates in aqueous media employ probes with two-electrode and three-electrode configurations. The two-electrode method generally exhibits an extended range of linearity compared to the three-electrode method. The basis of this extended linearity is analyzed with the help of general two-electrode equations. Existing methods are discussed for evaluating the corrosion rate of two electrodes corroding at the same rate and the mean corrosion rate of two electrodes corroding at different rates. A new method is described which allows separation of two-electrode polarization into individual anodic and cathodic polarizations of each electrode. This allows one to obtain the polarization curves, and hence the polarization resistance and corrosion rate of each electrode, with good accuracy.