Discussion about the Data Distortion of an Induction Probe Caused by Localized Corrosion

The data distortion of a 20# steel probe was analyzed by SEM, metallographic microscopy and EDS. The macro and micro morphologies showed that some corrosion pits were distributed on the surface of the probe. The results of metallographic analysis revealed that the material of the probe was qualified and the crystal structure was uniform. The results obtained from EDS indicated that some chloride ions and sulfur element were accumulated in the corrosion pits. The un-uniform covering and the influence of corrosive medium caused the localized electrochemical corrosion and even induced some corrosion pits. More corrosion pits resulted in moer change of the value of resistance and thus induced the data distortion.