Impact of Thin Film Coatings on Cathodic Protection

Thin film coatings, such as fusion bonded epoxy (FBE) coatings have become more popular as an underground pipeline coating especially on large diameter pipelines. This together with improved construction techniques has resulted in very effective coatings. They do however present additional considerations in a cathodic protection design. This paper deals with some issues that one must bear in mind related to cathodic protection when dealing with these superior coatings including a modification to empirical data in cathodic protection pre-designs, an upper polarized potential to prevent cathodic disbondment, inspection in horizontal directionally drilled crossings, an increased effect of telluric currents and an increased possibility of hazardous induced AC potentials. Examples are presented and discussed.