Detection of Subsurface Metal Oxidation with Thermal Imaging

We introduce thermographic imaging as a non-destructive evaluation method for detection of hidden corrosion or delamination of coating on metals or other substrates. A hybrid experimental-numerical technique using long wave, broad band imaging for the standoff and quantitative analysis of the interface is introduced. Time lapsed measurements of surface temperature is carried out, followed by numerical simulation of the corresponding thermal signature. Results of damage detection using thermal imagery were compared with substrate wall thickness measured by a thickness gauge. It is concluded that imaging approach provides measures of metal loss, at levels less than the variations in the metal wall manufacturing tolerance, highlighting corroded areas which would otherwise be undetectable using sensors for measuring metal thickness.