Corrosion behavior of carbon steel in piperazine solutions for post-combustion CO₂ capture

The corrosion behavior of A106 carbon steel in 30 wt.% piperazine (PZ, a cycling amine) solutions was investigated by potentiodynamic polarization, EIS, LPR, SEM/EDS, and XRD. For comparison, the corrosion was also conducted in the benchmark solvent of monoethanolamine (MEA) solution. Similar to MEA, initial corrosion testing results in PZ solvent showed that the corrosion rate increases with increases either in CO₂ loading from 0.23 to 0.43 mol CO₂/mol alkalinity (C/N) or in temperature from 20 to 80 °C. Short term corrosion investigations showed an approximately two orders of magnitude lower corrosion rate for A106 in 0.43 C/N CO₂ loaded 30 wt.% PZ at 80 °C than in the same conditions but with 30 wt.% MEA. The difference was due to the ability to form a dense and protective FeCO₃ layer on the metal surface in PZ as opposed to in MEA solutions. Possible mechanisms are discussed.