In oil and gas production at gravel bags, nozzles, a.s.o. erosion corrosion is a major problem. Production rates are often limited by critical fluid velocities which in most cases are unknown. A new combined flow loop - jet impingement pilot plant has been established to determine mass loss rates in a mixed gas - saltwater - sand multiphase flow at velocities up to 80 m/s. Investigated materials were those applied in oil- and gas fields (various stainless steel grades). Conditions in a gas conensate well have first been investigated using a gas - oil - ratio of 3 x 103 and 27 g/l NaCl containing water as liquid phase. Sand content with grain size below 150 µm was corresponding to practice. CO2 with a partial pressure of 15 bar was used as gas phase. Fluid flow and particles distribution have been calculated by multiphase computational fluid dynamics modelling of the impingement cell and verification of these data was done with particle image velocimetry. Mass loss rates have been determined after 72 h exposition time with optical profilometry with detection limit of 50 nm. Damaged surfaces were investigated by SEM.