Due to corrosive and hostile environment, in-service nonmagnetic pipes are prone to such anomalies as the external corrosion which poses a severe threat to structural integrity. Gradient-field Pulsed Eddy Current technique (GPEC) has been found superior to other non-destructive evaluation (NDE) techniques particularly pulsed eddy current testing in evaluation and imaging of subsurface corrosion in planar conductors. In this paper, GPEC for evaluation and imaging of external corrosion in nonmagnetic pipes is investigated. Two orthogonal gradient-field signals are simultaneously acquired and used for visualization of external corrosion. Through experimental investigation, it has been found that: (1) the depth of the external corrosion can be implied by the acquired corrosion images; and (2) the corrosion boundaries can be detected and identified via GPEC.
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