NIST Finds That Ethanol-Loving Bacteria Accelerate Cracking of Pipeline Steels

From NIST Tech Beat: August 2, 2011
Contact: Laura Ost
303-497-4880

U.S. production of ethanol for fuel has been rising quickly, topping 13 billion gallons in 2010. With the usual rail, truck and barge transport methods under potential strain, existing gas pipelines might be an efficient alternative for moving this renewable fuel around the country. But researchers at the National Institute of Standards and Technology (NIST) caution that ethanol, and especially the bacteria sometimes found in it, can dramatically degrade pipelines.
At a conference this week,* NIST researchers presented new experimental evidence that bacteria that feed on ethanol and produce acid boosted fatigue crack growth rates by at least 25 times the levels occuring in air alone.

Micrograph of crack in X52 steel after the sample was subjected to mechanical forces for several days in an ethanol solution containing acid-producing bacteria, Acetobacter aceti. Researchers at NIST's biofuels testing facility found that the bacteria increased fatigue crack growth rates at least 25-fold compared to what would occur in air. Credit: Sowards/NIST View hi-resolution image

The NIST team used a new biofuels test facility to evaluate fatigue-related cracking in two common pipeline steels immersed in ethanol mixtures, including simulated fuel-grade ethanol and an ethanol-water solution containing common bacteria, Acetobacter aceti. Ethanol and bacteria are known to cause corrosion, but this is the first study of their effects on fatigue cracking of pipeline steels.

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