Characterisation and evaluation of paint-coated marine corrosion in carbon steel using eddy current pulsed thermography

Marine atmospheric corrosion is a major challenge for carbon steel. Eddy current pulsed thermography (ECPT) can characterise defects under coating, but it is necessary to consider samples' surface geometry. This paper proposes a statistical approach for paint-coated S275 steel corrosion evaluation based on ECPT. The thermal response curve skewness of each point is utilised to reveal the corrosion region. The normalised skewness avoids the influence of emissivity anisotropy and surface geometry; corrosion can be evaluated by taking excitation coil skewness as a reference. In the results, the differential skewness drops monotonously with corrosion aggravation in 6 months, decreasing more than 90% from the uncorroded zone to the 3-month corrosion sample. The approach provides high sensitivity and detectability in paint-coated corrosion evaluation.