Critical fluid velocities and erosion corrosion rates are often limiting production rates in oil and
gas production. A combined flow loop - jet impingement pilot plant has been used to determine
mass loss rates in mixed gas - saltwater - sand multiphase flow conditions at impact velocities
up to 60 m/s. Artificial brine with a salt content of 27 g/l was used as liquid phase. The sand
content, with grain size below 150 µm, was up to five times higher than field conditions to
accelerate testing. CO2 at a pressure of 1,500 kPa was used as the gas phase.
Rectangular stainless steel samples were cut out from bars and pipes, mechanically ground
and polished prior to testing. Damaged surfaces of specimens exposed to the high velocity
multiphase flow were investigated by stereo microscopy, scanning electron microscopy (SEM)
and an optical device for 3D surface measurements. Metallographic cross sections of the
tested samples were prepared to characterize the microstructure underneath the damaged
surface areas. Electrochemical investigations according to ASTM G 61 were performed to
determine electrochemical behavior of tested materials including critical pitting potentials Epit
and repassivation potentials Erepass.
The influence of impact velocity on mass loss rates (penetration rates) of an austenitic, a
martensitic and a duplex stainless steel grade are presented. Effects of chemical composition,
pitting resistance equivalent number (PREN), microstructure and mechanical properties are
critically discussed.
Keywords: erosion corrosion, multiphase flow, stainless steel, PREN, microstructure