Patent ID: 7940062

Claim:
A method for estimating a condition of a coating on a portion of a coated pipeline buried in soil using a magnetometer, comprising: conducting a magnetically-detected electrochemical impedance spectroscopy (MEIS) test at a location over a selected segment of the buried pipeline; compensating for undesirable interfering and/or stray current signals flowing through the test location by generating at least one sinusoidal signal having a predominant amplitude and frequency and adding said sinusoidal signal to an output signal from the magnetometer; and switching between operation modes of a dual-mode potentiostat for performing a calibration step and performing the MEIS test; wherein the potentiostat includes a galvanostat and calibration mode of operation includes generating a complex calibration factor for each frequency by injecting a constant current from the galvanostat down the pipeline segment and measuring a resultant magnetometer output, and wherein during the MEIS mode of operation the calibration factor is used to compute actual on-pipe current at the location.