Influence of interface-related parameters on some heat stable salts in the corrosion studies of carbon steel for post-combustion CO2 capture

The effect of flow and temperature on the corrosion behavior of carbon steel in an aqueous methyldiethanolamine solution containing different heat stable salts, such as sodium sulfate, sodium sulfite and sodium thiosulfate, has been studied. The introduction of flow and increase in temperature generally caused an increase in the corrosion rate of carbon steel but the presence of the heat stable salts affected the corrosion behavior to different extents. Sulfate increased the corrosivity of the aqueous methyldiethanolamine solution, thus showed accelerated corrosion behavior in the presence of flow and with increase in temperature when compared with the solution without heat stable salts. The presence of sulfite reduced the corrosivity of the methyldiethanolamine solution due to its oxygen scavenging ability. Although flow and temperature stimulated an increase in the corrosion rate of carbon steel, the corrosion inhibiting effects of sulfite ions increased with the salt concentration. Also, the presence of sodium thiosulfate caused a reduction in carbon steel corrosion. Its inhibition ability is largely the result of the formation of FeS product layer resulting from its disproportionation reaction. This layer offered a slight resistance to the influence of flow and increase in temperature when compared with the system without heat stable salts.