Permeating hydrogen effect on the protective performance of a composite film consisting of corrosion inhibitors and iron oxides used in CO₂ utilization related environment

The protection provided by corrosion inhibitors for the internal surfaces of pipes or equipment used in CO₂ utilization environments is critical. However, the protective performance of the inhibitor can be significantly compromised by the permeating hydrogen generated from the external wall surfaces of the pipes or equipment. This problem becomes more severe when the inhibitors adsorb onto the iron oxides on the internal surface. In this study, we simulated permeating hydrogen by electrochemically generating it and investigated its effect on the protective performance of a composite film composed of 2-mercaptopyrimidine and iron oxides on X70 steel. The results indicate that permeating hydrogen can alter the structure and composition of the oxide layer, making it more defective. This facilitates the penetration of corrosive species through the composite film to the substrate. Additionally, permeating hydrogen can change the composition of the oxide layer, reducing Fe₂O₃ to FeO, which hinders the adsorption of 2-mercaptopyrimidine, leading to inhibitor desorption. Consequently, the integrity of the composite film is compromised, and its protective performance deteriorates significantly.