Electrochemical investigation of the corrosion behavior of chromium-modified carbon steels in water

Electrochemical measurements were performed on four steels with different chromium (Cr) contents in simulated CANDU reactor coolant at room temperature to investigate the influence of chromium content on the corrosion behavior of the steels. The addition of chromium to carbon steel can promote passivation. The passive film significantly decreases the corrosion rate, and thus improves the corrosion resistance of the steels as chromium content is increased. Repassivation kinetic experiments indicate that there is a more rapid repassivation rate and a more stable passive film on steels containing a higher concentration of chromium. The slip-oxidation model was used to calculate the crack growth rate (CGR) on the steels. The 304L stainless steel has the highest CGR with an increase in potential of the steels studied. Chromium modification of steels can improve the resistance to corrosion. However, its influence on cracking and crack growth must be taken into consideration. The 2.5%Cr-1%Mo steel gave the best overall results when considering both the corrosion and the cracking behavior of the steels studied.