Patent ID: 6054038
Filing Date: 2000-04-25
Classification: G01N

Abstract:
A method for early detection of electrochemical corrosion of a coated or an uncoated surface of a metal structure utilizing electrochemical impedance spectroscopy, comprising the steps of:(a) providing an electrochemical impedance spectrometer, said spectrometer comprising a computer controlled potentiostat and a sensor device which comprises a metal tip, said sensor device functions as both a counter and reference electrode;(b) placing the metal tip of the sensor device directly onto the top surface of the coated or uncoated surface of the metal structure;(c) wetting the surface of the metal structure around the metal tip with an electrolyte, the metal tip and the area covered by the electrolyte thereby defining a controlled detection area;(d) applying an AC voltage from the potentiostat across the metal tip and the metal structure to be tested, the metal structure thereby functioning as a working electrode;(e) measuring the resulting AC current thus obtaining a first reading;(f) performing steps (d) and (e) at different frequencies of AC voltage to obtain multiple readings;(g) calculating an impedance magnitude and phase for each obtained reading, thereby generating an impedance spectrum over the entire applied frequency range;(h) comparing the generated impedance spectrum of the controlled detection area with the impedance spectrum of previously determined measurements of metallic structures in different stages of known surface corrosion to determine the stage of surface corrosion of the metal structure being tested.