Early stage of deterioration in polymeric coatings detected by positron annihilation spectroscopy

In polymeric coating systems, positron annihilation spectroscopy has shown sensitivity in detecting the early stage of deterioration due to weathering, specially, in probing a specific location or depth of coatings from the surface through interfaces and the bulk. Existing extensive experimental positron data show that positron annihilation signals respond quantitatively to the deterioration process due to weathering. Now, it is possible to detect the very early stage of coating deterioration at the atomic and molecular scale by using positrons, typically in days as compared to years by conventional methods. This paper summarizes recent positron studies in polymeric coatings. Correlations between positron data and a variety of chemical, physical and engineering data from ESR, AFM, cross-link density, gloss, and cyclic loading are presented. A proposed application of positron annihilation spectroscopy as a real field inspection tool to detect coating deterioration of bridges is presented.