The Car and Truck Fleet and Leasing Management Magazine

Market Trends

Report Identifies Possible Cause of Corrosion in Systems Storing and Dispensing ULSD

November 12, 2012, by Mike Antich - Also by this author

There have been persistent reports of severe and accelerated corrosion in storage tanks and dispensing equipment, ever since the EPA mandated the introduction of ultra-low sulfur diesel (ULSD). On June 1, 2006, the sulfur content of ULSD was reduced from 500 parts-per-million (ppm) in low sulfur diesel (LSD) to 15 ppm in ULSD. One consequence of the reduced sulfur content was the creation of a more favorable environment for microbes and bacteria to develop and thrive. (See the July 27, 2010 Market Trends blog, “Uptick in Fuel-Related Problems in Diesel Trucks”.) Other known trade-offs to ULSD are increased costs (a few cents more per gallon), 1- to 2-percent less energy, and decreased lubricity requiring the use of additives and CJ-4 motor oil. In addition, the refining process that removes the sulfur also removes high-energy aromatics, which corresponds to a 1- to 2-percent increase in fuel consumption. However, what surprised many were the reported instances of accelerated corrosion in storage tanks and dispensing equipment in as little as six months.

Findings of an Independent Study
In response to industry concerns about unexplained accelerated corrosion, the Petroleum Equipment Institute surveyed the diesel fuel industry to identify issues with systems storing and dispensing ULSD. The survey revealed sporadic problems occurring in all regions of the country, regardless of the age of the equipment. As a result, the Clean Diesel Fuel Alliance (CDFA) was formed, which includes the American Petroleum Institute, Ford Motor Co., the National Association of Convenience Stores, the National Association of Truck Stop Operators, Petroleum Equipment Institute, Petroleum Marketers Association of America, Association of American Railroads, and Steel Tank Institute. The CDFA funded an independent research project by Battelle Memorial Institute to investigate corrosion in systems storing and dispensing ULSD.

The study’s conclusions were announced Sept. 5, 2012, in a 146-page report entitled, “Corrosion in Systems Storing and Dispensing Ultra Low Sulfur Diesel (ULSD), Hypotheses Investigation.” The Battelle study sampled six sites nationwide that reported accelerated corrosion in ULSD systems. Samples from the six sites were analyzed for genetic material and chemical characteristics. According to the report, among other contaminants, acetic acid was found at all sites from a variety of samples (fuel, water bottoms, vapor, and corrosion scrapings). In addition, the Battelle report stated ethanol was unexpectedly identified and measured at five of the six sites, along with the acetobacter microorganisms, in the majority of water bottom samples. The Battelle report hypothesized that the acetic acid is likely produced by acetobacter feeding on low levels of ethanol contamination. Battelle has identified this as the most likely cause of the corrosion. The report states, “The source of the ethanol is unknown; however, diesel fuel is often delivered in the same trucks as ethanol-blended gasoline. Also, some underground storage tanks for storing ULSD, which have been converted from gasoline tanks could have manifolded ventilation systems with gasoline tanks. Thus, it is possible that there be some cross contamination of ethanol into ULSD.”

However, this hypothesis has drawn criticism from the ethanol industry. It points out that, under normal, everyday storage and handling conditions, ethanol should never come into contact with diesel fuel since ethanol is a gasoline additive. It also said that none of the six sites sampled included manifolded ventilation systems. These critics also point out that Battelle’s report drew its conclusions from a very small sample set. In addition, the Renewable Fuels Association (representing the ethanol industry) was not included in the investigation and not given an opportunity to provide feedback. It is too early to draw definitive conclusions on how ULSD tanks are being contaminated with ethanol or why accelerated corrosion occurs in some ULSD tanks while other ULSD tanks remain largely unaffected. Some wonder whether the problem may be associated only with fiberglass reinforced plastic (FRP) tanks, since all the affected sites investigated have FRP tanks.

Although additives could play a role in creating a corrosive environment, the Battelle report said it is unlikely that they are the primary cause of the observed corrosion. Examples of additives include lubricity agents to help increase diesel fuel lubricity and detergent additives to clean fuel injectors.

What’s the Next Step?
The CDFA is currently deciding whether to move forward with further research. The Battelle report recommends additional research be focused on samples from a larger, more diverse set of underground storage tanks over a period of time. The study would sample and monitor ULSD tank systems with and without accelerated corrosion events and investigate the possible source of ethanol contamination. There continues to be many unanswered questions.

More research is needed to reach a definitive conclusion.

Let me know what you think.


  1. 1. Steve Kibler [ November 21, 2012 @ 07:24AM ]

    Very interesting article Mike. In my tiny scientific mind the solution seems simple. The root cause appears to be bacteria from"acetic acid likely produced by acetobacter feeding on low levels of ethanol." Why not regularly treat ULSD with a biocide? I then jokingly think of SNL's Father Guido Sarducci suggestion for promblems - "I say we nuke em" Hmmmm, that could work; what about UV bombardment?

  2. 2. Dave Harmon [ November 23, 2012 @ 05:21AM ]

    We have 5 -1500 gal diesel fuel trucks to dispense fuel to all of our off road equipment and highway trucks. We have been using

    ULSD diesel fuel since 2006 and have had no problems with corrosion in these truck tanks. We are a county located in Arizona and was wondering if our mild climate had any thing to do with this.

  3. 3. Melvin Garrett [ February 12, 2013 @ 12:42PM ]

    Thanks for the insight into an issue that many of us have been experiencing. Many of my colleagues and I have experienced diesel fuel tank issues since the introduction of USLD. Unfortunately, they problems have defied definition or explanation as to the cause by our traditional and historical methods of addressing fuel storage tank problems.

    Another possible insight I have gained from your editorial is; an understanding why Ford Motor company has taken the stance that their 6.7lL turbo diesel fails due to fuel system or emissions systems failures is not a warrantable failure, because the fuel is contaminated. I have heard of cases where warranty was denied on engines with 18,000 miles due to fuel contamination. My colleagues and I have been baffled as to how Ford could say the fuel was contaminated and caused the failures, when there are multiple fuel filters designed into the system by Ford for this engine. In fact we have hundreds of other diesel powered vehicles in our fleets running on fuel from the same fuel tanks without problems or any warranty issues from other engine manufacturers. I strongly suspect that Ford is using there involvement in this study and the results to bolster their confidence in claiming “fuel contamination” as the cause of all of their 6.7L engine failures.

Comment On This Story

Email: (Email will not be displayed.)  

Comment: (Maximum 10000 characters)  
Leave this field empty:
* Please note that comments may be moderated.

Fleet Incentives

Determine the actual cost of owning and running a vehicle in your fleet. Compare vehicles by class and model.

Sponsored by

SDK stands for Software Development Kit.

Read more

Author Bio

Mike Antich

Editor and Associate Publisher

Mike has covered fleet management and remarketing for more than 20 years and entered the Fleet Hall of Fame in 2010.

» More

More From The World's Largest Fleet Publisher