Localized Corrosion of Carbon Steel and Its Implications on the Mechanism and Inhibition of Stress Corrosion Cracking in Fuel-Grade Ethanol

Stress corrosion cracking (SCC) of carbon steel has been observed in fuel-grade ethanol (FGE, C(2)H(5)OH). Electrochemical behavior of carbon steel and therefore the role of localized corrosion in SCC has not been studied adequately because of the difficulty in performing electrochemical experiments in resistive environments such as FGE. A microelectrode technique was used in this work to conduct electrochemical studies in simulated FGE (SFGE). It was found that oxygen likely played multiple roles: it participated in the passive film formation in addition to its more commonly observed role in aqueous environments of changing the open-circuit potential (OCP), and it may also participate in the oxidation of ethanol on steel surfaces. A model, based on this dual role of oxygen, was proposed to explain the SCC mechanism of carbon steel in SFGE. The model is supported by the inhibitor evaluation work, which also demonstrated that carbon steel SCC could be inhibited by adding inhibitors.