Feasibility Evaluation of Chemical Inhibition of Ethanol SCC

Stress corrosion cracking (SCC) has been observed in carbon steel tanks and piping in contact with fuel grade ethanol (FGE) in user terminals, storage tanks, and loading/unloading racks. Detailed laboratory studies, sponsored by American Petroleum Institute (API), Renewable Fuel Association (RFA), Pipeline Research Council International (PRCI), and Pipeline and Hazardous Materials Safety Administration (PHMSA), demonstrated that, in ASTM D-4806 FGE, dissolved oxygen was the most important factor leading to SCC, followed in importance by pre-existing scale on the steel, chloride, and methanol. In a Roadmapping Workshop conducted in October 2007, methods to avoid oxygen contamination in ethanol and defining safe operating limits in terms of ethanol chemistry and oxygen concentration were identified as major gaps in the safe transportation of ethanol in pipelines. Using inhibitors to prevent SCC in FGE is a possible solution, but the impact on the fuel end use applications needs to be considered. The ability of the inhibitors to prevent SCC was evaluated under flowing conditions created by jet impingement, which is believed to simulate pipe flow in the pipelines. The results established the baseline for inhibitor performance in mitigating carbon steel SCC and provided insights in the feasibility of SCC prevention by chemical addition. Furthermore, an electrochemical method was developed for rapid evaluation of inhibitors in FGE. This method was supported by the understanding of the oxygen role in promoting SCC and the mechanistic study performed in this work and in previous projects. The present project continued to address the gaps that remained after the PRCI SCC 4-3 Phase II: (1) The crack growth tests under flowing condition are to be performed to determine whether the inhibitors would perform similarly in flowing solution similar to that which would be encountered in transmission pipeline; (2) A rapid method to select inhibitor for carbon steel SCC mitigation is still to be developed; and (3) Among the inhibitors that were demonstrated effective in mitigating carbon steel SCC in FGE, it would be beneficial to know if they would perform well below currently used dosage. The objectives of the project were: (1) Evaluate the performance of selected inhibitors in long term crack growth experiments under flowing conditions simulated by jet impingement; (2) Develop a method to rapidly evaluate and select SCC inhibitors for use in FGE; and (3) Evaluate the feasibility of chemical inhibition of carbon steel SCC in FGE.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; Tables;
  • Pagination: 63p

Subject/Index Terms

Filing Info

  • Accession Number: 01640213
  • Record Type: Publication
  • Report/Paper Numbers: Report No. 2012-9192, Project No. EP021141
  • Files: TRIS, ATRI, USDOT
  • Created Date: Jun 20 2017 9:36AM