Corrosion Service Company Limited (CSCL) was retained by PRC International to review current installation and monitoring practices used in the pipeline industry for minimizing coating damage and for determining the effectiveness of cathodic protection at HDD crossings.
A research plan was developed that included six tasks to address the project objectives. In general, it was intended to coordinate field testing at an actual HDD crossing site, by using the local deep and shallow groundbeds and installing multiple coupons at various depths.
The main finding of the testing indicated that...
The main finding of the testing indicated that the deep sections of the HDD in drilling mud behaved as a deaerated environment, requiring very low currents to polarize to highly electronegative levels. To achieve similar environmental conditions to those experienced by the HDD pipeline, deep coupons are strongly recommended, with additional work required to determine the most suitable backfill(s). Only small differences were observed between the efficiency and effectiveness of local shallow and deep groundbeds. Caution is recommended extending the conclusion about very low current requirements to all HDDs, especially due to reported corrosion. Therefore, additional testing on other environments (i.e. granite) is strongly recommended.