Degradation of fusion bonded epoxy pipeline coatings in the presence of direct current interference

In this work, the effects of direct current (DC) interference on properties and performance of fusion bonded epoxy (FBE) pipeline coating in a simulated soil solution was studied by measurements of water permeation and electrochemical impedance spectroscopy, as well as characterization by scanning electron microscopy and Fourier transform infrared spectroscopy. Results demonstrate that the presence of DC interference increases the water permeation into the coating, and decreases the resistance of the coating for corrosion protection. Moreover, the DC changes the molecular structure of the coating material. Generally, the FBE coating located in the cathodic zone suffers from more serious degradation than that in the anodic area due to the opposite direction of the DC induced electric fields in the two zones, which affect the diffusion and accumulation of water molecules and chemical ions.