Parameters influence in steel corrosion evaluation using PEC thermography

Pulsed eddy current (PEC) thermography is proposed as a powerful Nondestructive Testing and Evaluation (NDT&E) technique, allowing operators to observe the heating developed from the eddy current distribution in a structure using infrared imaging, detecting defects over a relatively wide area within a short time. In this paper, PEC thermography is investigated to detect corrosion in structural steel components. The transient response at corrosions is a complex mix of many factors including electrical conductivity, permeability, thermal conductivity, heat capacity, density, depth, size, and exposure time which all have to be taken into account in the analysis of the PEC thermography. Firstly, the Finite Element Modeling (FEM) of corrosion with different parameters is established and numerical simulation is conducted in COMSOL Multiphysics. Next, structural steel (S275) samples with naturally produced corrosion are tested and experimental studies are carried out. The surface thermal profile and two related features are presented to evaluate the corrosion with different exposure time. The work shows that PEC thermography can be used for the detection and characterisation of corrosion through analysis of the surface thermal images and maximum temperature at heating and cooling stage.