Electrochemical sensors for evaluating corrosion and adhesion on painted metal structures

A method for the early detection of electrochemical corrosion, metal and coating degradation utilizing an inexpensive, in situ, and nondestructive electrochemical sensor, for detection of corrosion of coated metallic structures (e.g. bridges, aircraft, ground vehicles, storage tanks, buildings, or ships) comprising the steps of:

• (a) providing an in situ sensor for producing an output correlative to an identifiable impedance spectrum (i.e., the impedance magnitude and phase as a function of the frequency of the applied voltage, created utilizing ac Impedance or Electrochemical Impedance Spectroscopy (EIS)) comprising a two electrode sensor responsive to atmospheric, water uptake, incubation, and corrosion to produce differences in impedance spectra utilizing, as one electrode, conductive ink deposited on the coating as a counter/reference electrode, eliminating the need for a remote or counter electrode by electrolyte immersion;
• (b) applying a small electrical voltage between the metallic substrate of the structure as the working electrode and the counter/reference electrode and measuring the resulting current based upon the applied voltage between the electrodes;
• (c) converting an analog signal indicative of the measured current to a corresponding ac impedance signal;
• (d) providing a potentiostat's microcomputer with an operational program representative of a functional expression which correlates to distinctive impedance signatures;
• and
• (e) converting the impedance spectrum as a function of accelerated exposure and interpreting the said spectrum to determine the stage of corrosion the metal and/or coating has experienced.