Detection of Corrosion under Coated Surface by Eddy Current Testing Method

Corrosion under insulator (CUI) is a damage of materials due to a reaction between a surface of steel and an insulation layer. The CUI can generate an impact greatly on the industry, because it can occur in equipment without warning. An inspection system was designed to detect the CUI from the outside of a steel plate using a non-destructive testing associated with the eddy current technique. This research is to develop a prototype device and software for CUI detection by using low-cost equipment. 600-1000 Hz sinusoidal signals induced by a sine wave function generator were applied to detect CUIs, and the results were demonstrated by the proposed CUI detection program. The experimental results reveal that the pick-up coil with laminated core probe can detect the CUIs effectively, and the designed sinusoidal eddy current system with the proposed CUI detection program can monitor and detect the CUIs with up to 3 mm insulation thickness.