Equipment World Digital Magazine
Issue link: https://read.dmtmag.com/i/107622
maintenance | by Tom Jackson TJackson@randallreilly.com ULSD and corrosion Unexplained corrosion of steel tanks has experts wondering if ethanol is the culprit. If so, how did it get into diesel? S ince the introduction of Ultra Low Sulfur Diesel in 2007, a growing number of diesel storage tanks and dispensing systems have experienced unusual and accelerated corrosion problems. The kind of corrosion that might take 10 or 20 years previously was showing up in as little as 30 to 60 days, says Edward English, vice president and technical director for Fuel Quality Services.* In 2009 the Petroleum Equipment Institute brought together experts representing manufacturers, oil companies, ASTM and the underground storage tank industry to try to get some answers. Later, the task force would fall under the Clean Diesel Fuel Alliance. Like the plot in a good murder mystery, the task force has found a lot of suspects, but the identity of the culprit is yet to be proven conclusively. Investigations continue and English thinks a solution should be found within the next year or so. But in the meantime, the possibility of rapid, mildsteel corrosion should prompt contractors who use diesel fuel to be extra vigilant about the health of their tanks, monitor the quality of Without detection, remediation or treatment, traces of ethanol in your diesel may cause widespread corrosion on mild steel elements in your fuel system, as shown here on this fuel filter stud and faceplate. their fuel and practice good housekeeping. Searching for a cause At first, many in the industry wanted to blame ULSD for these corrosion problems, says Howard Chesneau, president of Fuel Quality Services, because the problem began to emerge about the same time the industry switched over to ULSD. But ULSD is not corrosive by itself. Further investigation found traces of ethanol in ULSD. Ethanol isn't corrosive, but when combined with water in the fuel, it becomes a "food source" that is conducive to the growth of acetobacter, a type of bacteria. This bacteria converts (oxidizes) ethanol into acetic acid, which is highly corrosive to mild carbon steel. As it turns out the switch to ULSD occurred about the same time gasoline manufacturers started putting ethanol in gasoline. It is likely that trace amounts of ethanol-blended gasoline get into the diesel fuel as delivery tankers switch from one product to the next – what the industry calls switch loading. Small amounts of gasoline contamination have always occurred with switch loading, but it was never seen as a problem until the introduction of ethanol-blended gasoline. Ethanol and water have one thing in common: they love each other, more than gasoline and diesel fuel. So when ethanol-entrained diesel fuel is discharged from a tanker into *Fuel Quality Services, (fqsinc.com) provides biocides, stabilizers and additives plus testing, training and consultation related to fuel issues. EquipmentWorld.com | February 2013 27