Correlating Corrosion Field Data With Experimental Findings for the Development of Pipeline Mitigation Strategies

Coating disbondment on pipelines is a common phenomenon that leads to exposure of the pipeline metal to ground water solutions, promoting a corrosive environment which is associated with stress corrosion cracking (SCC). This investigation aims to understand the corrosion behavior and rate of pipeline steel under coating disbondments of varying sizes based on field data and experimental studies. In the analysis of the field data, dig reports provided by a Canadian gas transportation company were analyzed for cases of anaerobic corrosion under tape coatings. The analyzed field data provided a correlation between the tape coating disbondment size and corrosion rate found under the coating. The experimental studies aimed to understand the field findings. The analyses were performed on X-65 pipeline steel coupons placed in a vertical coupon holder with a PMMA shielding. To imitate the variation in the disbondment size, the gap size between the metal coupons and the shielding was varied (2 mm, 5 mm, and 10 mm, and infinite). The general corrosion rates were obtained through weight loss calculations. The experimental results were compared and correlated with dig-report data from the field for a development of cathodic protection and pipeline mitigation strategies.