Corrosion performance of carbon steel and 304 stainless steel in activated methyldiethanolamine solution using autoclave tests

This study evaluated the corrosion performance of carbon steel (CS) and 304 stainless steel (304 SS) under high temperature and pressure (inside an autoclave) in a CO2-saturated solution of activated methyldiethanolamine (aMDEA). The aim was to determine the effect of temperature, presence of chloride ions, degradation of the aMDEA and amount of dissolved oxygen on the corrosion resistance of these materials. The results indicated that raising the temperature between 50 and 120°C led to a higher corrosion rate of both CS and 304 SS. However, the corrosion rate of 304 SS decreased and remained stable at higher temperatures as the corrosion reaction became mass-controlled. Oxygen loading results in the passivation of both CS and 304 SS. The amine degradation products were found to accelerate the corrosion rate of CS at 50°C due to a chelation effect of iron ions, and also increase the corrosion rate of 304 SS at 120°C by causing the passive film rupture. The SCC test on U-shaped 304 SS samples showed transversal microcracks with a depth of more than 25 µm after 2 months of immersion in an autoclave containing CO2-saturated aMDEA at 120°C, which confirmed the SCC risk of 304 SS.