SURFACE TRANSIENT TEMPERATURE INVERSION FOR HIDDEN CORROSION CHARACTERIZATION - THEORY AND APPLICATIONS

Corrosion in metals is simulated with variations in plate thickness wh ich are laterally infinite in a 1D model and are represented by milled flat-bottom holes in a 2D model. Temperature contrast over corroded a reas is chosen as an informative parameter, quite independent of absor bed thermal energy in the infra-red thermographic test. It is shown th at, due to lower sensitivity to rear-side effects at the beginning of the thermal process-and increasing 3D hear diffusion effects at the en d of the process, there is an optimum time to detect corrosion. A robu st inversion function is proposed and its stability against variations in tested material, heat pulse duration and observation time is analy sed using numerical modelling. Corrosion in a steel specimen of 1.3 mm thickness is experimentally studied, having proved the validity of th e inversion algorithm with an average accuracy of 17% for material los s ranging from 74 to 14%.