Statistical Approach to Corrosion under Disbonded Coating on Cathodically Protected Line Pipe Steel Available to Purchase

Quantitative prediction models for the corrosion of cathodically protected line pipe steel under a disbonded coating were presented. The optimization plot for the cathodic protection (CP) of crevices beneath a disbonded sleeve applied at the girth weld joint was presented using the multiple quadratic regression analysis by considering the results of numerical modeling and the overprotection problems. It is possible to predict and evaluate the CP status under a disbonded coating using this plot. A model based on the stepwise multiple regression analysis reflecting the contribution of chemical, microbial factors of the soil environment, and that of the effectiveness of CP was presented to predict the maximum corrosion depth of steel pipes under a disbonded coating where the CP current could not penetrate effectively. The results showed that the predicting equation successfully explained the field corrosion phenomena.