b' Marketer InformationRules & RegulationsNO DEFINITIVE ANSWERS in Newly Released Study on the Cause of Accelerated Corrosion of UST Systems Containing ULSDW The Coordinating Researchoperating at retail stations in the field. Taken together, Washington, D.C. - Council (CRC), a non-profit research arm of thethese earlier studies suggest accelerated corrosion petroleum equipment and automotive industryin ULSD tank systems is widespread, occurs incon-recently released a final report on a major researchsistently, with no discernable pattern, and involves project aimed at identifying the causes of acceler- microbial activity possibly brought on by ethanol ated corrosion in underground storage tank systemscontamination together with the presence of water. containing ultra-low sulfur diesel fuel (ULSD). TheIn contrast, a CRC study focused on laboratory Mark S. Morgan, Esqstudy is important to energy marketers because itcontrolled-condition tests using corrosion coupons, PMAA Regulatoryreports that accelerated corrosion in UST systems issmall strips of metal subjected to various microbial Counsel more widespread than initially thought and continuesactivity. This in-lab approach was taken to isolate spe-to grow. EMA has been an active participant in thecific factors that could influence corrosion including accelerated corrosion research since the phenomenonsulfur content, water, microbes in the fuel, biodiesel was first identified in 2008 and continues to workcontent, ethanol contamination, and diesel fuel ad-closely with the US EPA to identify its causes.ditives. In the study, different statistical measures Tank owners first reported the presence of acceler- were used to determine which factors truly impact ated corrosion in UST system equipment as far backcorrosion. However, no conclusions were drawn on as 2007. Initially, it was thought that the removal ofwhether any one factor slightly increased or decreased sulfur from diesel fuel that began in 2007 under thecorrosion. Nevertheless, the key findings of the study EPA ULSD program was somehow connected to thecan be summarized as follows:sudden appearance of accelerated corrosion in diesel WATER, more than any other factor, was clearly fuel tank systems. Or, possibly it was due to the growth of biodiesel blending that caused the condi- linked to corrosion. All test conditions containing tions to induce accelerated corrosion. Study of thefree water experienced corrosion.problem was in its infancy at the time and specula-MICROBIAL growth occurred in tanks in the tions as to the causes of accelerated corrosion werepresence of water resulting in increased corrosion.all over the map. What was certain however, was thatIt is less clear that externally added microbe colonies tank owners were increasingly reporting discovery ofcaused greater corrosion than natural colonies.a corrosive material resembling used coffee groundsFUEL SULFUR content did not have a strongcoating submersible turbine pumps, drop tubes,correlation with corrosion. However, some analyses sensor probes and dispenser components in USTshowed an increase in corrosion rates with increas-systems containing ULSD. Reports indicated thating sulfur content.the corrosion formed quickly, without warning, and disabled newly installed UST equipment in as littleTHE BIODIESEL content in ULSD had no strongas a month. The problem was typically discoveredor clear correlation with corrosion.when recently installed fuel filters suddenly clogged. The corrosion seemed to follow no established pat-ETHANOL was found at very low levels in diesel tern. Accelerated corrosion could appear in one retailfuel, likely due to cross contamination in handling. diesel fuel tank, but not in a competitors similar tankThe combination of ethanol and some microbes can across the street. The problem was not isolated to anylead to acetic acid formation which might contribute one geographic area and no specific atmospheric orto increased corrosion on the tank bottom or in the weather patterns were identified as ideal to promotevapor space above the fuel level. This observation accelerated corrosion. Instead, the phenomenonsupports the hypothesis that acetic acid formation is spread out unevenly across the North, South, East andlinked to microbial action on ethanol contamination Western regions of the country. in the diesel fuel UST (by which pathway ethanol Two studies were initially undertaken to discover thecontaminated the diesel fuel has not been defini-cause of the accelerated corrosion; one by the Cleantively established).Diesel Alliance, partially funded by PMAA (nowThe full CRC accelerated corrosion report can be down-EMA) and the other by the U.S. EPA. Both studiesloaded at https://crcao.org/wp-content/uploads/2021/07/were limited to conducting research on UST systemsDP-07-16-01-FINAL-REPORT-REV-30JUL21-COMPLETE.pdf . 16 www.wpma.com / Autumn 2021'