Stripping Quality of Three Layer Polyethylene Coating on High Strength Steel Pipeline in Western Region

A field investigation was conducted on the anti-corrosion layer of a three-layer polyethylene (3PE) on a high-strength steel pipeline in the west. At the same time, scanning electron microscopy (SEM) observation, energy spectrum (EDS) analysis, cross-section thickness test and other methods were used to analyze the surface of the fusion bonded epoxy (FBE) at typical exfoliation positions, and the reasons for the failure of the anti-corrosion layer were explored. The results showed that the anti-corrosion layers found on site at 3 positions were stripped, and two of them were related to the control parameters of the anti-corrosion layer preparation process. The main cause of peeling was that the epoxy powder curing degree didn't meet the requirement. The coating thickness and surface cleanliness control also had certain problems. In addition, one failure was related to the mechanical damage caused by construction. The coating near the damage site was peeled off under the action of cathodic protection.