Multiphase-flow-induced corrosion and cavitation-erosion damages of API 5L X80 and API 5DP grade S steels

Abstract

The objective of this work is to establish a performance classification based on the mass loss of API 5L X80 and 5DP S steel drill pipes caused by multiphase-flow-induced corrosion and cavitation. Multiphase-flow-loop tests were conducted using a mixture of 20% heavy oil (150 cP) + 80% deionized water, containing 15% of sodium chloride, at 40 °C under a partial CO2 pressure of 2.0 bar. Cavitation-erosion tests were performed in deionized water at 40 °C with a horn vibration frequency at 20 kHz. The corrosion and wear resistance were evaluated by measurements of accumulated mass loss, Scanning Electron Microscopy, X-ray Dispersive Energy and X-Ray Diffraction. The results showed the formation of a corrosion product layer, consisting of FeO (OH) and FeCO3, presenting a corrosion attack due to the hydrodynamic effect. The turbulent flow led to a rupture of the protective layer exposing the metal surface to the corrosive medium. The corrosion mass loss of the 5DP steel was lower than the X80 steel. Cavitation-erosion test results showed that the mass loss of the 5DP steel was lesser than the X80, showing a higher cavitation resistance of the former. Finally, some suggestions to mitigate the multiphase-flow-induced corrosion were proposed.