Effect of particle velocity and impact angle on the corrosion-erosion of AISI 304 and AISI 420 stainless steels

The effect of particle velocity and mean impact angle on the corrosion-erosion of solubilized AISI 304 and quenched and tempered AISI 420 stainless steels was studied. The tests were performed using slurry composed of 0.5 M H2SO4 + 3.5% NaCl and 30 wt% quartz particles with 0.21-0.30 mm mean diameter. Potentiodynamic curves, AFM and SEM analyses allowed identification of the wear mechanisms and assessment of the degree of surface damage. The slurry temperature was monitored and pH of solution and solid contents of the slurry were fixed during the tests. The results obtained for AISI 304 steel showed a gentle degradation regime for normal incidence and low impact velocity (4.5 m s−1), while a severe degradation regime was found for grazing incidence and high impact velocity (8.5 m s−1). The severe condition was characterized by intense plastic strain and formation of lips and prows. Mechanical effects were predominant over the corrosive ones, and the surface behaved mainly in a ductile manner. The results obtained for AISI 420 steel revealed a marked corrosion influence on degradation mechanisms. Moderate degradation was predominant at low impact velocity, while severe damage arose for higher velocities and both grazing and normal impact. Uniform, intergranular, pitting corrosion and corrosion-assisted erosion were the main degradation mechanisms. The higher corrosion-erosion resistance of the AISI 304 was attributed to its better response to corrosive attack, this factor being more relevant than hardness.