DEPASSIVATION AND REPASSIVATION OF AISI321 STAINLESS-STEEL SURFACE DURING SOLID PARTICLE IMPACT IN 10-PERCENT H2SO4 SOLUTION

Erosion-corrosion experiments on AISI321 stainless steel in 10 wt.% H2SO4 + 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 depissivation 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-conosion 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 an the fresh specimen surface.