Understanding corrosion behavior of Q420 steel in low temperature environment with freezing-thawing cycling

The corrosion behavior of Q420 steel under constant temperature and freezing-thawing conditions is investigated. The steel exhibits the highest corrosion rate at 25 °C and the lowest corrosion rate at -30 °C, while the steel that undergoes freezing-thawing cycling shows lower corrosion rate than that at 0 °C. The localized corrosion is significantly affected by the temperature variations, with the samples corroded under freezing-thawing conditions showing the highest pit number density and the highest possibility of the pit initiation. The samples immersed at 0 and 25 °C show comparable pit size with higher pit depth, diameter, and volume, attributed to the higher rate of pit propagation along the vertical and horizontal directions. Galvanic corrosion results demonstrate that there are areas of activated metal under the ice, which form microcells with surrounding unaffected areas, attributed to the local ion concentration and the water crystallization.