ELECTRICAL AND ELECTROCHEMICAL MEASUREMENTS AS PREDICTORS OF CORROSION AT THE METAL-ORGANIC COATING INTERFACE

Five types of electrical and electrochemical measurements are reviewed: D.C. electrical properties, A.C. resistance, capacitance, corrosion potential, and polarization curves. When the coating resistance decreases with time and falls below 106 to 107 ohms/cm2, corrosion beneath the coating is occurring at a significant rate. A low electrical resistance requires (a) ion and water penetration into the coating, (b) ready motion of ions through the coating, and (c) proceeding ionic/electron transfer reactions (corrosion) at the polymer-metal interface. Care must be taken when making electrical measurements that the measurement itself does not affect the corrosion rate. © 1979.