Effect of preferential dissolution on erosion-corrosion for chromium steel in alkali slurry

An investigation was carried out concerning the effect of preferential dissolution on the erosion-corrosion for a chromium steel in 1mol/L NaOH. Preliminary tests using a potentiodynamic technique were performed in order to establish the presence of preferential dissolution in the alkali solution with and without the alumina particles at different rotation speeds. For purposes of quantifying the observed phenomena a potentiostatic mass loss method was also used. The results show that the active peaks occur at potential between +0.4 and +0.5V on the polarization curves, which indicates that there is a preferential dissolution for chromium steel under erosion-corrosion conditions and the ferrite phase acts as a sacrificial anode in favor of (Fe,Cr)7C3 phase. Addition of particles can promote the preferential dissolution at different rotation speeds. The combined effects of erosion-corrosion results in total mass loss rates to be greater than the sum effects of each process taken alone, thus showing a strong synergism between erosion and corrosion due to preferential dissolution.