Abstract
A field study was carried out to investigate if the use of tarpaulin (Tarp) to cover FBE System 1A coated pipelines can protect the coating from ultraviolet (UV) degradation. Actual outside weathering exposure tests for 24-months were conducted on FBE System 1A coated samples with and without Tarp covering. Changes in the coating Flexibility, Photo-oxidative Index (POI) and Carbonyl Index (CI) were examined at different time intervals during the exposure period. The pipeline coating with a Tarp protector showed no reduction in flexibility and only small changes in POI and CI, which indicated that the Tarp successfully protected the pipeline coating from physical and chemical degradation. The pipeline coating without a Tarp protector showed a noticeable decrease in flexibility and increase in POI and CI of the FBE System 1A coating after continued outdoor exposure. Comparison of these results to previously published work on FBE coated samples that were “protected” by UV light blocking topcoats showed that even though the topcoats were successful in stopping UV induced photo-oxidation, the flexibility of the coating system decreased over time. The previous results indicate that the reduction in flexibility of the FBE coating system may be due to factors other than the photo-oxidative damage of the topmost portion of the coating system. Limited DSC studies showed evidence of molecular coordination (long term relaxation) leading to new, less flexible physical structures of the unprotected samples. The DSC results suggest that the flexibility reduction may be attributed to the cumulative effects of photo-oxidation and physical ageing.
