Quantitative Assessment of Subsurface Oxidation in Coated Materials

A hybrid experimental-numerical method for the standoff and quantitative analysis of metal corrosion under protective coatings is proposed based on long-wave infrared broadband imaging. This approach is based on time-lapsed measurements of surface temperature and a numerical simulation of the corresponding thermal signature. Experiments were carried out to verify the proposed methodology, while identifying the limitations and opportunities for using imaging for quantitative assessments of corrosion, particularly for use in infrastructure health monitoring. This included field studies on large natural gas pipelines in service. Results from the imaging campaign were simultaneously compared with point sensor measurements that are used customarily for pipe wall thickness evaluation, demonstrating that the full field approach provides measures of metal loss that is less than the variations in the pipe wall thickness in the noncorroded state. (C) 2017 American Society of Civil Engineers.