Depassivation and repassivation of AISI321 stainless steel surface during solid particle impact in 10% H 2SO 4 solution

Abstract

Erosion-corrosion experiments on AISI321 stainless steel in 10 wt.% H 2SO 4 + 15 wt.% corundum sand were carried out by means of a rotating system with the specimen on the edge of a disc. Dynamic polarization curves during erosion-corrosion were measured at different rotating rates and the weight-loss kinetics was studied at different applied potentials and rotating rates. The straining electrode technique was used to simulate the depassivation and repassivation processes during erosion-corrosion. The experimental results showed that in the whole passive region the apparent passive current density and the weight loss during erosion-corrosion were constant at the fixed rotating rate and increased quickly with the rotating rate in the range of flow rate from 2.5 to 10 m s −1. The dissolution behaviour of the straining electrode at different applied potentials and straining rates was found to correlate with the dynamic polarization current of specimens during erosion corrosion, indicating that the electrochemical corrosion in the erosion-corrosion process was controlled by both the depassivation caused by the solid particle impact and the regrowth of protective film on the fresh specimen surface.