Study of the adhesion of three-layer pipeline coatings

摘要

External pipeline protection has been achieved for years in the oil and gas industry by usingthree layers polyolefin (3-LPO) coatings under cathodic protection. In the last few years,various cases of disbondment at the FBE / steel interface have been observed without defectsin the coating on pipes. Disbondment is a major threat in corrosion protection as the coatingwill shield the cathodic protection. So far, no corrosion was observed underneath disbondedcoatings, but understanding this phenomenon seems necessary to avoid further problems.This study aims at understanding the mechanisms of disbondment of 3-LPO.First, this paper focuses on the permeability to water, ions and oxygen of the coatings,showing that if ions have long times of diffusion, water and oxygen reach the surface very fastin comparison with the twenty years of a pipe lifetime.Then, tests of adhesion were performed on FBE samples on steel after various times ofimmersion in water at 60°C in order to correlate the diffusion data to the loss of adhesion.