The electrochemical response of stainless steels in liquid-solid impingement

High-alloy stainless steels exhibit complex corrosion behaviour under liquid-solid impingement conditions compared with in static conditions. In this study the corrosion resistance under erosion-corrosion conditions and the overall erosion-corrosion resistance were examined for high-alloy stainless steel UNS S32654 and a standard austenitic stainless steel (UNS S31603) at 18 and 50degreesC in 3.5% NaCl with solid loadings ranging from 10 to 6000 mg/l. It has been found from this study that, as expected, high-grade stainless steel UNS S32654 exhibits better corrosion and erosion-corrosion resistance under all the conditions applied. The benefits from alloying additions such as Mo, Cr, N have been demonstrated to be in the reduction of the metal dissolution rate when the surface is depassivated and superior repassivation performance. Also, the electrochemical response has been monitored as a function of solid loading, impinging velocity and temperature. The critical levels of solid loading and velocity at which a transition from flow-induced corrosion to erosion-corrosion takes place have been determined in this study giving an indication of the resistance of the passive film to mechanical breakdown. (C) 2004 Elsevier B.V. All rights reserved.