Role of the Jet Angle, Particle Size, and Particle Concentration in the Degradation Behavior of Carbon Steel under Slow Slurry Erosion-Corrosion Conditions

Erosion-corrosion behavior of piping systems is a critical issue for their durability. This work concerns the erosion-corrosion behavior of carbon steel as a function of abradant characteristics as particle size and concentration. Degradation tests were performed in a jet erosion-corrosion cell with a maximum flow rate of 4.8 m/s, and jet angles comprised 30 degrees and 90 degrees. Abradant particles consisted of angular alumina powder with a mean diameter of 181, 219, and 359 mu m. A critical threshold flow velocity of about 2.5 m/s was determined when experiments were performed with particles with diameters of 181 mu m and jet angles of 45 degrees. Even if erosion did not occur, the degradation rate increased compared with the stagnant condition because of dissolved dioxygen supply. A maximum of erosion-corrosion of 4 mg x cm(-2) x h(-1) was determined for the jet angle of 45 degrees, irrespective of the particle sizes. The increase of abradant concentration led to a higher degradation rate regardless of the jet angle. However, the degradation rates tended to limit values of 7 mg x cm(-2) x h(-1) at 45 degrees and 5 mg x cm(-2) x h(-1) at 90 degrees. Above a critical concentration, a slowdown of the degradation was measured, suggesting that particle behavior in dense fluid acts on material degradation. This critical concentration can be understood from the interactions of the particles in concentrated media that modify trajectories in the flow and at the metal surface, reducing their kinetic energy consequently.