Electrochemical study of steel corrosion in MEA medium during CO2 capture

The most promising technology presently used for CO2 capture from flue gas is reversible chemical absorption using amine-based solvents. In such industrial processes, corrosion represents one of the major operational problems. An appropriate selection of the structural and component materials is required to minimize this problem. Tests of corrosion resistance in CO2 capture with MEA have been carried out in pilot plants by Laborelec using different types of steels as testing materials. Follow-up of the pilot installation degradations has also been performed. In this context, some unexpected degradations were observed, suggesting different hypothesis and mechanisms that have not been confirmed yet. Those results also suggest a possible need to use higher grades of structural material.

Laboratory tests were further carried out. Different metals were aged for one month in MEA at different temperatures. The weight loss was measured to compare the different materials and assess the impact of the test conditions. Indeed, many parameters could be responsible of the premature corrosion. Identify the role of each parameter and determine the corrosion mechanism is thus essential to select the appropriate materials for the capture structural materials.

To reduce the testing time and be able to follow the evolution of the corrosion behaviour of the metallic materials, electrochemical techniques were used in combination with immersion tests in the aggressive medium. Austenitic stainless steel (316L) and carbon steel (DC04) were used as rotating disc electrodes. The corrosion rate was followed as a function of time by determination of polarization resistance (Rp) with an optimized setup (acquisition parameters, rotating speed,...). The results showed that electrochemical techniques allow a short-time evaluation of the impact on corrosion rate of temperature, the presence of different gases (O2, CO2,...), the presence of metallic ions,....

In addition to the electrochemical characterization of the metal, we were also able to monitor the MEA degradation. Cyclic voltammetry on a gold electrode was used in order to check the evolution with time of the ideally polarizable domain. The obtained results are promising and show the possibility to use classical electrochemical techniques as a precise tool to study the corrosion kinetics occurring during CO2 absorption and desorption and to perform an appropriate selection of the materials.