Contributions of corrosion and erosion in the erosion-corrosion of Sanicro28

Corrosion, erosion and synergism behaviors of Sanicro28 (UNS-N08028) stainless steel have been studied during erosion-corrosion using a slurry impingement rig. The erosive-corrosive slurry solution consisted of 3.5% NaCl saline water and 30 g/l SiO2 erodent particles. The erosion and erosion-corrosion tests were performed at jet velocities of 4, 6, 7.5, and 9 m/s under two impingement angles of 40 and 90 degrees. The corrosion behavior of the alloy in both stagnant and erosion-corrosion conditions was studied by electrochemical impedance spectroscopy and polarization techniques and the synergy was calculated. The results showed that corrosion, erosion, erosion corrosion, and synergy rates of the alloy increased as the impact velocity increased. An increase up to 10(4) times was observed in the corrosion rate during erosion-corrosion as compared with the stagnant condition. There were about 28 times increase in the corrosion rate and 25% decrease in the corrosion potential as the impact velocity increased from 4 to 9 m/s during the erosion-corrosion. A higher corrosion rate and a lower corrosion potential were also obtained at the normal incident compared with impingement angle of 40 degrees. The removal rates showed a critical velocity of 6 m/s in both the erosion and erosion-corrosion conditions, however, the transition was not clear in the electrochemical results. It was found that the change of erosion wear due to corrosion was higher than the change of corrosion due to erosion under various conditions indicating that the synergy rate was highly dependent on the effect of corrosion on erosion.