Erosion-Corrosion of Carbon Steels in a Laboratory: Three-Phase Flow

A new testing facility for a high-velocity, three-phase flow consisting of a gas flow loop and a jet impingement rig is described. Flow velocities between the nozzle and specimen have been determined through computational fluid dynamics (CFD) simulations and by particle image velocimetry. Tests were conducted on typical carbon steels (J55 and C95) that are used in tubings for the gas and oil industry. Flow conditions of a sweet gas condensate well have been applied. Mass-loss rates have been determined after testing times of between 4 h and 168 h using optical profilometry. Damaged surfaces were investigated using optical and scanning electron microscopy. The effects of material and flow velocity on the mass-loss rate have been investigated. Mass loss of specimens under given conditions is determined by siderite formation and increasing degradation of siderite layer by impacts of sand and fluid droplets. Degradation happens by erosion-enhanced corrosion. Normalized steel J55 behaves like a ductile material resulting in a maximum degradation rate under small impact angles outside the focal spot. Compared to J55 the quenched and tempered material C95 shows a generally lower depth of attack with its maximum degradation under large impact angles, indicating a brittle behavior. Cementite of pearlite may act additionally as a cathode and accelerate corrosive attack.