Corrosion effect of Carbon steel SA106 Gr. B in oxalic acid

The corrosion behavior of Carbon Steel (CS) SA106 Gr. B in an organic condition of oxalic acid (OA) was elucidated under the anticipated conditions of a Pressurize Heavy Water Reactor (PHWR) during the chemical decontamination. CS specimens were exposed in the acidic medium for 18 h at 95 °C to evaluate the corrosion activity. Atomic Absorption Spectrometry (AAS) was employed to analyze the dissolved Fe concentration and found to be 276.5 and 401.3 ppm in 10 mM and 20 mM OA solution, respectively. Corrosion rates were assessed using the weight loss method. The CS specimens dissolved in 20 mM exhibited a corrosion rate of 6.3 mm/y while that dissolved in 10 mM OA has 4.6 mm/y. The corrosion products were characterized by Electron Probe Microanalysis (EPMA). The intergranular corrosion (IGC) was observed prior to the formation of corrosion products and oxalate passivation, potentially providing pathways for contaminant diffusion into the bulk substrate.