Investigation of Passivation Characteristics of X65 Pipeline Steel in Ethanol Fuel Environments

Investigation of Passivation Characteristics of X65 Pipeline Steel in Ethanol Fuel Environments

Growing interest in the use of alternative fuels has led to an increase in production of fuel grade ethanol (FGE), necessitating an efficient method of transportation for this biofuel. Occurrences of stress corrosion cracking (SCC) of pipeline steels in FGE have spurred studies toward understanding the phenomenon of this environmentally assisted corrosion. Prior work in simulated fuel grade ethanol (SFGE) has shown that water, chloride ions, dissolved oxygen, and acidity are all major factors in the promotion of SCC of pipeline steel. In this research, passive film characteristics and passivation kinetics of X65 pipeline steel in FGE environments are explored. Results of scratch tests performed to compare passivation kinetics of X65 steel in FGE environments containing chloride, oxygen, and water will be presented. Electrochemical measurements and in-situ Raman spectroscopy aided in characterization of passive layer composition, while XPS of FGE-exposed steel coupons helped identify passive layer composition and elucidate passive film characteristics.

KEYWORDS: Biofuels, Passive film, Fuel grade ethanol, Pipeline steel