Evaluation of Stress Corrosion Cracking Behavior of Steel in Multiple Ethanol Environments

Significant concerns currently exist regarding the stress corrosion cracking (SCC) behavior of steel pipeline and terminal facilities used to handle fuel grade ethanol. Various factors have been associated with ethanol SCC (eSCC) of carbon steels and include conditions that promote crack initiation and growth, corrosion potential, dissolved oxygen concentration levels, water content, and the chemical species of the ethanol itself. Recently, a comprehensive laboratory testing program was conducted to investigate and compare the eSCC behavior of different fuel grade ethanol feedstocks under varying test conditions. The testing methodology included notched slow strain rate (N-SSR) tests for the determination of crack growth rates, and threshold stress intensity for SCC using a fracture-mechanics based approach. The N-SSR tests were further augmented with electrochemical characterizations and pre- and post-test chemical analyses of the ethanol solutions. This paper discusses the testing approach and summarizes the key findings of this program.