Investigation of pitting corrosion monitoring using field signature method

• Low detection accuracy of pitting corrosion in FSM was analysed.
• A mathematical model was established to solve pitting corrosion.
• The detection accuracy can be greatly improved.

The field signature method (FSM) is a nondestructive testing (NDT) method based on the potential drop (PD) technique and has been applied to online metal pipe corrosion monitoring for nearly three decades. The many advantages and benefits of the method have been reported in a number of studies, but few have reported on its limitations or shortcomings. However, the detection accuracy for pitting corrosion in FSM is very low. In this paper, the reasons for the low pitting corrosion detection accuracy of FSM were analyzed and it was found that different corrosion pits, which have different sizes, depths or positions, generally have differing influences on the potentials of nearby electrode pairs. Therefore, a new method using a subdivided resistor network to assess pitting corrosion is proposed and verified. When compared with the traditional method, the most important parameter, namely the pitting corrosion depth detection accuracy, can be significantly improved.

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