Abstract
Fusion Bonded Epoxy (FBE) coating has been used for corrosion protection of underground pipe lines since the 1960’s. FBE provides protection of pipeline under cathodic protection even though there may be dis-bondment or blistering. FBE does not shield cathodic protection current under normal conditions, a characteristic which likewise distinguishes FBE coating from all other coating. In this paper failure analysis methodology will be applied to the principal mechanisms by which FBE coatings fail during long term service; with specific application to case studies involving blistering. The case studies apply standard failure analysis techniques to determine the primary causes and modes of failures. Solution in blistered areas, pH and presence of cations and chlorides on the surface and in the coating will provide evidence for surface contamination/dis-bondment mechanism. If AC interference or shielding is present, localized corrosion attack in blistered areas can be detected prior to deep penetration in to wall thickness by effective corrosion monitoring. This can be achieved by on-time monitoring of soil corrosivity and AC/DC interference by test coupons.
