Inhibition of Carbon Steel Stress Corrosion Cracking in Fuel Grade Ethanol by Chemical Addition or Oxygen Control: A Feasibility Evaluation

Carbon steel is susceptible to stress corrosion cracking (SCC) in fuel grade ethanol (FGE). The SCC can be mitigated by either adding chemical inhibitors or removing oxygen. The present work studied the performance of inhibitors under flowing condition that simulated pipe flow using crack growth rate tests. Oxygen scavenger performance was also evaluated by slow strain rate (SSR) tests and crack growth test. A large scale flow loop test was also performed to evaluate the scavenger performance. The results suggest that the inhibitors that demonstrated effective in mitigating SCC in SSR tests under stagnant conditions also performed well under flowing condition. The feasibility of SCC mitigation using these two methods was evaluated based on the experimental results and economic considerations. Although oxygen control was demonstrated to be effective in the laboratory tests, removing oxygen from large volumes of FGE may not be a viable option to mitigate SCC. Thus, inhibitor addition may be a more reasonable option to mitigate SCC of carbon steel in FGE considering inhibitor application is a well-established operation practice in pipeline operation in combating general corrosion.