Role of magnesium ions in reducing high temperature aqueous corrosion of carbon steel

Carbon steel is used as the primary heat transport system piping material in pressurized heavy water reactors. The carbon steel surfaces corrode during the high temperature operation. Enhanced wall thinning of the piping in locations of high velocity and neutron activation of corrosion products pose serious operational difficulties. Magnesium ion modified water chemistry resulted in significant reduction in the corrosion and corrosion release of carbon steel. The changes induced by magnesium ions in the various processes at the metal–oxide, oxide–solution interfaces, and subsequent restructuring of the oxide were identified by in situ electrochemical impedance spectroscopy.

► Corrosion of carbon steel reduced by 40% in the presence of magnesium ions.
► Uptake of magnesium ions in the corrosion product oxide confirmed by LRS and XPS.
► Altered corrosion processes seen in EIS studies.
► Mg modified oxide at inner oxide–solution interface alters anodic reaction kinetics.
► Electrical conductivity of Mg modified oxide alters cathodic reaction kinetics.