In the erosion-corrosion system all erosion corrosion tests were performed under sweet gas conditions. The plant is a combination of a closed gas circuit - "flow loop" and a jet device - "jet impingement". The maximum erosion - corrosion rate was measured with a 3D microscope. First, the influence of the impact angle was tested at 30, 60 and 90 °. It was investigated that the corrosion rates of carbon steel J55 at impact angles of 30 and 90 ° were at same level. The impact angle of 30 ° was chosen for all subsequent experiments because it simulates approximately a pipe flow. The influence of flow velocity was measured at carbon steels J55 (ferritic-pearlitic) and L80 (tempered martensite). The velocities were 0,2 (drop impingement), 10 and 30 m/s. The maximum corrosion depth was obtained at a velocity of 30 m/s. The corrosion of steel J55 at this flow velocity is almost four times high as at the steel L80. Steel J55 was tested under influence of two different inhibitors. First, on inhibitiv dose of inhibitor 1 to reach on efficiency of 70 to 90 % was determined. The result was a dose of 1000 ppm of inhibitor 1, which was also chosen for inhibitor 2. The inhibition effect of inhibitor 1 was approximately 70 %, of the inhibitor 2 nearly 100 % at 10 m/s. Steel L80 was tested under worst case conditions (30 m/s) with a dose of 1000 ppm inhibitor 2. The result was also an inhibitor efficiency of 100 %.