Effects of the wire mesh on pulsed eddy current detection of corrosion under insulation

Pulsed eddy current (PEC) technique has been used to detect corrosion under insulation (CUI) for decades, but whether and how the wire mesh laid in the insulation layer affects the detection remains ambiguous. This paper touches on this issue for the first time. The insulated structure was simplified to a carbon steel plate covered by a cladding with an air gap representing the insulation layer, in which the wire mesh was situated. Finite element simulations were performed on the simplified model and found that the aluminium or stainless steel wire mesh had little effect on eddy currents in the plate, while the mild steel wire mesh could cause a considerable increase in the probe footprint and a significant drop of the eddy current density. For the mild steel wire mesh, the magnetic permeability and wire diameter were the main factors affecting the probe footprint and eddy current density. Afterwards, simulations were conducted to analyse the effect of the mild steel wire mesh on the PEC probe performances for evaluating the CUI depth and found that the mild steel wire mesh led to decreases in both the PEC signal amplitude and decay rate. The simulation results were finally verified by experiments.