Considering that a distinct advantage of the electrochemical noise technique is that no perturbation is introduced to the corrosion process, the physical effect of connecting two corroding electrodes by a measuring resistor must be examined initially (Fig. 1). If a corroding electrode and a reference electrode are immersed in an electrolyte, the corrosion potential can be measured without introducing significant perturbation to the corrosion process provided that the impedance of the voltmeter is high compared with the impedance of the corroding electrode. If this assumption is verified, the current flowing between the reference electrode and the corroding electrode is negligible, and the corrosion process is unperturbed. Thus, all the charge associated with, for example, an anodic event on the electrode is consumed by the cathodic reaction on that electrode. If a second identical electrode and a second reference electrode are immersed in the same electrolyte, each of the two electrodes corrodes independently; all the charge generated by one event on one electrode is consumed on the same electrode, and the corrosion potentials of the two electrodes are uncorrelated. Thus, the introduction of a second disconnected electrodes does not introduce a perturbation to the fundamental corrosion process on the first electrode and viceversa