The sample size diameter exposed to the measurement is only 1 mm. Since the current measured here is in pA or nA range, a Potentiostat / Galvanostat with very high accuracy for low current measurements is preferred. Electrochemical Noise or ZRA is a popular corrosion technique. This set-up suits the measurements where test specimen cannot be cut, or if the coupon is non-flat in geometry. Typically, the analysis involves a series of “Spot” type corrosion measurements directly on surface of their specimen. Such analysis is also very popular in checking corrosion propagation in museum artifacts where techniques like SECM is not an option.