SCC OF CARBON STEEL IN FUEL ETHANOL SERVICE: EFFECT OF CORROSION POTENTIAL AND ETHANOL PROCESSING SOURCE

摘要

Stress corrosion cracking (SCC) of carbon steel in fuel ethanol service has been observed in an increasing number of failures in the last few years. This increase in failures is also due to the increasing use of ethanol for fuel applications. However, these failures have reportedly occurred only in terminal storage tanks and other associated equipment but not at the ethanol producer locations. The work being presented herein is an extension of an American Petroleum Institute (API) sponsored project that seeks to elucidate the specific factors that play a role in this SCC phenomenon. The effect of corrosion potential and ethanol processing source was investigated to determine the differences in SCC between laboratory grade ethanol, samples from ethanol producers and E-85 fuel ethanol. In the previous study, corrosion potential as influenced primarily by dissolved oxygen was identified as the most important SCC factor. In the presence of oxygen, all of the samples evaluated in this study produced varying degrees of SCC, except for one of the producer ethanol samples. This sample was found to have a corrosion potential which appeared to be well outside of the cracking potential range. The reason for the high corrosion potential in this sample is still unknown and more detailed analysis of the sample chemical make-up is needed. Slow strain rate testing (SSRT) and electrochemical testing methodologies were employed in this particular study along with some chemical characterization techniques.