CORROSION RESISTANCE OF Fe–Al/Al2O3 DUPLEX COATING ON PIPELINE STEEL X80 IN SIMULATED OIL AND GAS WELL ENVIRONMENT

Abstract

Corrosion resistant Fe – Al / Al 2 O 3 duplex coating for pipeline steel X80 was prepared by a combined treatment of low-temperature aluminizing and micro-arc oxidation (MAO). Phase composition and microstructure of mono-layer Fe – Al coating and Fe – Al / Al 2 O 3 duplex coating were studied by X-ray diffraction (XRD), scanning electron microscope (SEM) with energy dispersive spectrometer (EDS). Corrosion resistance of the coated pipeline steel X80 in a simulated oil and gas well condition was also investigated. Mono-layer Fe – Al coating consists of Fe 2 Al 5 and FeAl , which is a suitable transitional layer for the preparation of ceramic coating by MAO on the surface of pipeline steel X80. Under the same corrosion condition at 373 K for 168 h with 1 MPa CO 2 and 0.1 MPa H 2 S , corrosion weight loss rate of pipeline steel X80 with Fe – Al / Al 2 O 3 duplex coating decreased to 23% of original pipeline steel X80, which improved by 10% than that of pipeline steel X80 with mono-layer Fe – Al coating. It cannot find obvious cracks and pits on the corrosion surface of pipeline steel X80 with Fe – Al / Al 2 O 3 duplex coating.