Materials Performance Supplements

Corrosion Prevention and Control for Tanks 2017

Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.

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4 MAY 2017 MATERIALS PERFORMANCE TANK CORROSION CONTROL SUPPLEMENT TO MP metal components in UST systems storing diesel fuel in the United States could be a very common occurrence," the EPA says. "It appears from our research that corrosion inside of UST systems could result in an increased chance of releases of fuel to the environment and subsequent groundwater contamination." The corrosion was geographically wide- spread and affects UST systems with both steel tanks and fiberglass tanks, and it poses a risk to most internal metal components, the agency says. Across the samples, the EPA observed corrosion occurring on all types of UST system metal components, including submersible turbine pump shafts, automatic tank gauge (ATG) probe shafts, risers, over- fill equipment such as flapper valves and ball valves, bungs around tank penetration, inner walls of tanks, and fuel suction tubes. "Corrosion of some metal components could hinder their proper operation and possibly allow a release of fuel to occur, or continue unnoticed," the agency says. B e c a u s e of h o w n e w th e p r o b l e m appears to be, the EPA explains that it has very little verifiable data about how equip- ment functionality and integrity are being affected by this corrosion. At the moment, the EPA says it has heard anecdotes of functionality failures of release prevention equipment and leak detectors, as well as failures of metal walls resulting in leaks into secondary containment areas. " Howe ver, that information shoul d become more available as owners become more aware of the findings of our research, a n d c o r ro si o n i n U STs st o r i n g di e s e l becomes more visible," the EPA says, add- ing that even if fuel is not released into the environment, severe corrosion still poses significant concerns for UST owners. The EPA says that its data and analysis could not pinpoint a single cause for the corrosion that UST owners began report- ing in 2007. Rather, it appears that multiple underlying factors and corrosion mecha- nisms could be contributing. One such factor is microbiologically inf luenced corrosion (MIC). The agency notes that prior research suggests reduced sulfur in diesel could be allowing microbial life to proliferate in ultra-low sulfur diesel tanks and, through MIC, cause corrosive conditions that are less possible in USTs storing low-sulfur diesel (not ultra-low). T h e E PA b e l i e v e s t h a t f o l l o w i n g enhanced maintenance practices can min- imize MIC risks by either reducing the bac- terial populations or preventing an envi- ronment where microbial life can thrive. The agency notes that its Office of Research and Development hypothesized that biofuel components in diesel, such as ethanol and biodiesel, could be providing the energy source for microbial populations. Th e research shows that ethanol was present in 90% of the 42 UST samples, suggesting that the cross-contamination of diesel fuel is likely the norm. Statistically, the EPA says that the par- ticulates and water content in the fuel were closest to being significant predic- tive factors for metal corrosion. But the researchers caution that causation cannot be discerned based on this study. Moving forward, the EPA says it is continuing to work collaboratively with partners in the UST community, industr y, and scientific experts on additional laboratory research on the cause of corrosion. Recommendations on Next Steps While the EPA says it cannot project the actual percentage of USTs storing diesel in USTs storing diesel are particularly prone to issues of rust and corrosion, according to the EPA's recent study. The EPA's research shows ASTs with diesel also possess a heightened corrosion risk.

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