The electrochemical response of stainless steels in liquid–solid impingement

Abstract

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 50 °C 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.