Abstract

Fusion Bonded Epoxy (FBE) internal coating pipe is a kind of internal coating technology for piping and pipeline, which has a good corrosion resistance, and had become one of the important measures of corrosion control for pipes in oil & gas fields. A high temperature resistant FBE with primer Internal coating system of pipe was chosen as the experimental object, and conducted long period (30 days) immersion tests and electrochemical impedance spectroscopy (EIS) tests of the FBE coatings under various temperatures with high content of CO2-H2S-Cl-, combined morphology observation & adhesion performance test to study the corrosion resistance and corrosion mechanism of the FBE with primer internal coating system under various high temperatures. The results showed that no visible corrosion damage was found on FBE coating surface at high temperature with high content of CO2-H2S-Cl-condition. However, there had been obvious local damages such as small cracks and holes on the coating surface by microscopic morphology analysis at high temperature condition. The corrosion damage of the FBE with primer internal coating system is the most severe at 150° C , and H2S corrosion occurred on the substrate; EIS test results showed that the coating resistance Rcoating and the interface transfer resistance Rct were significantly reduced with the increase of temperature, and the corrosion process was accelerated. At 150° C service condition, the coating resistance and interface transfer resistance Rcoating decreased the most. Correspondingly, the coating pull-off adhesion (10.19MPa) at 150° C decreased by approximately 53% compared with the original coating system (21.75MPa), which showed a largest decrease.

Introduction

In 1950s, as an important measure to improve the corrosion resistance of base metal, internal coating pipes was first applied to sour crude oil and natural gas pipelines [1]. Among the coating systems, FBE coating has good impact resistance, bending resistance, high bonding strength, good resistance for acid, alkali, salt, oil and water fluid. The coating can reduce the internal surface roughness friction resistance of piping & pipeline to reduce project investment.

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