ELECTROCHEMICAL SENSOR FOR MONITORING ATMOSPHERIC CORROSION OF POLYMER-COATED METAL

Sensors which use electrochemical impedance spectroscopy (EIS) to monitor in situ the corrosion of polymer coated metals in atmospheric conditions have recently been developed. The validity of these sensors, which consist of a gold grid deposited on top of the organic coating, has been tested in a cyclic corrosion test in which electrocoated samples sprayed with 0.5 or 5.0 wt-%NaCl were exposed to wet and dry conditions for alternate periods. It was found that when delamination was significant, the equivalent circuit should include the interfacial impedance of the gold electrode. Furthermore, it was observed that the features of the EIS spectra were dependent on both the delamination rate and the conductivity of the thin electrolyte film present on the paint during exposure. (C) 1995 The Institute of Materials.