An In Situ Raman-Electrochemical Investigation of Carbon Steel Corrosion in Na[sub 2]CO[sub 3]∕NaHCO[sub 3], Na[sub 2]SO[sub 4], and NaCl Solutions

The anoxic corrosion of carbon steel liners inside failed copper nuclear waste containers is dependent on the composition of the groundwater to which it is exposed. The influence of carbonate/bicarbonate, sulfate, and chloride in solutions simulating concentrated groundwaters at pH 8.9 on the composition of the corrosion products formed on A 516 Gr 70 carbon steel has been investigated at room temperature. In situ Raman spectroscopic identification of the corrosion products formed during polarization at constant potential was conducted in a spectroelectrochemical cell. Siderite was established as the main product in sodium carbonate/bicarbonate solutions, and the observance of iron carbide indicates extensive steel dissolution in this environment. In mixed carbonate, sulfate, chloride solutions, compact deposits of carbonate-containing, and to a lesser degree, sulfate-containing green rusts were formed, along with small amounts of magnetite. In chloride-dominated solutions very thin, compact films, undetectable by Raman spectroscopy, were formed. Ex situ Raman analysis suggests this film may be magnetite.