Corrosion in Underground Storage Tanks (USTs) Storing Ultra-Low Sulfur Diesel (ULSD): EPA Research on Risks, Prevalence, Causes, and Next Steps
Presented at the National Tanks Conference
September 16, 2015 Ryan Haerer
EPA Office of Underground Storage Tanks
Outline What is ULSD Corrosion? ◦ The problem ◦ Impacts ◦ Potential causes
What do we do with the results? ◦ Educate ◦ Address issues ◦ Update standards and practices ◦ Further research into prevention
and treatment
EPA’s Research Study ◦ Overview ◦ Key Findings ◦ Conclusions
Corrosion in USTs Storing ULSD Reports began around 2007 Internal metal components – often STP shaft Severe and rapid onset Yet unidentified cause Extent not fully known Appearance different and impacts more severe than corrosion in sump spaces of USTs storing gasoline/ethanol blends
What do we know about the possible cause?
Reports of corroded metal equipment in vapor space of USTs storing ULSD – first in 2007
Two changes to fuel supply around same time ◦ Reduced sulfur content in diesel beginning 2006 (500ppm LSD to 15ppm ULSD)
◦ Increased production and use of ethanol and biodiesel*
2012 Hypotheses Investigation by Clean Diesel Fuel Alliance of 6 UST storing ULSD * Energy Independence and Security Act of 2007 expanded Renewable Fuel Standard, setting volumetric blending targets for renewable fuels
Corrosion Risks to the Environment – Exposed Metals in the Vapor Space
Release prevention equipment could fail to function ◦ Corrosion on flapper valves could restrict movement and allow an
overfill ◦ Product level floats get stuck on corroded shafts and fail to signal a
rising product level, fuel release, or water infiltration
◦ Ball float valves – ball or cage may corrode
◦ Line leak detectors failing performance testing at higher rates
Some Observed Corrosion Examples –
Corrosion Risks to the Environment – Bottoms of Tanks
Metal components could corrode completely and possibly release fuel to environment
◦ ULSD prone to collect water and sludge in bottom of tanks
◦ Some jurisdictions seeing much higher rates of bottom failures of
primary walls of double-wall steel tank bottoms since ULSD
◦ Single-wall tanks possibly leaking undetected
Some Observed Corrosion Examples
Costs of Metal Corrosion for Owners
Increased pace of filter changes
More frequent servicing of equipment
Shorter lifespan before replacement of equipment
Findings from Clean Diesel Fuel Alliance 2012 Hypotheses Investigation
◦ Not conclusive, but suggested microbiologically influenced corrosion (MIC) a possible cause worth further research
◦ Microbes feed on ethanol present in ULSD, creating acetic acid
◦ Ethanol possibly entering ULSD through switch-loading of trucks wherein a gasoline-ethanol load is followed by a diesel one, or by diesel and gasoline-ethanol blend UST’s sharing the same vent line.
Ethanol can be converted into acetic and butyric acid (and possibly into glycolic acid)
Could other factors be in play? ◦ Glycerol can also be converted to corrosive acids
◦ Propionic acid presence in 2012 suggests this possibility
◦ Glycerol (possibly) in biodiesel, biodiesel possibly in ULSD* ◦ Allowable concentration from production, or
◦ Out of specification biodiesel
◦ Likely that a combination of factors involved
*ASTM D975 allows biodiesel to be blended into ULSD up to 5% without being labeled biodiesel
Glycerol into glyceric, lactic, and propionic acids
2014-2015 Study on the Corrosion of Metal Components in USTs Storing ULSD
Environmental Protection Agency Office of Underground Storage Tanks (OUST)
Battelle Memorial Institute
UST owner volunteers and industry partners, esp. CRC Diesel Corrosion Panel – could not have made the study happen without them! Thank you!
Provided critical site access for real-world data collection Provided data input on tank history and management practices Critical review of study design and draft reports
What did we set out to accomplish with the 2014-2015 Research Effort?
For continuity- ◦ Build on previous research and help figure out
how to address the problem ◦ Allow others to build on what we find
To better understand the extent of the problem and potential risks identified in the limited reports we’ve heard
Identify correlations among UST systems with severe or minimal corrosion
Definitively pinpoint a specific cause – every UST is unique
Identify specific solutions to the problem
Research designed: This research was NOT intended to:
Identify Volunteers for a Diverse UST Sample Population
• 10 geographic clusters • 42 sites • 24 fiberglass, 16 steel, 2 steel coated • 8 of 10 have steel and fiberglass in cluster
• 8 owners
• Government, retail, fleet • Single and multiple site • Large range of fuel throughputs and suppliers
• Diverse USTs
• 1 – 29 years in service • 5,000 to 20,000 gallons in capacity • Different product storage histories • Various approaches to maintenance
0
4
8
12
16
20
5,000 6,000 7,000 8,000 10,000 12,000 15,000 20,000
# of
UST
s
Tank Capacity (gallons)
42 USTs by Capacity and Material
Steel Fiberglass
Collect Data on UST Conditions at Each Site
Inspect with internal tank video
Collect samples: • Vapor • Fuel • Water bottom
Collect information on maintenance, throughput, fuel supply, biocide use, etc.
Sample Analyses
FUEL
Fuel Analysis Methods Method Identifier Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration (Procedure B)
ASTM D63048 Water Content
Determination of Density, Relative Density, and API Gravity of Liquids by Digital Density Meter ASTM D405210 Density
Acid Number of Petroleum Products by Potentiometric Titration ASTM D66411 Total Acid Number
Determining Corrosive Properties of Cargoes in Petroleum Product Pipelines NACE TM-17212 Corrosion Rating
Particulate Contamination in Middle Distillate Fuels by Laboratory Filtration ASTM D621713 Particulates Determination of Biodiesel (FAME) Content in Diesel Fuel Oil Using Mid Infrared Spectroscopy (FITR-ATR-PLS Method)
ASTM D737114 Biodiesel Content
Flash Point by Pensky-Martens Closed Cup Tester ASTM D9315 Flashpoint
Determination of Free and Total Glycerin in Biodiesel Blends by Anion Exchange Chromatography
ASTM D759116 Free and Total Glycerin
GC-MS Full Scan Lab In-House Method Unknowns of Interest
Determination of Total Sulfur in Light Hydrocarbons, Spark Ignition Engine Fuel, Diesel Engine Fuel, and Engine Oil by Ultraviolet Fluorescence
ASTM D545317 Sulfur Content
Electrical Conductivity of Aviation and Distillate Fuels ASTM D262418 Conductivity
Determination of Short Chain Fatty Acids by Gas Chromatography-Mass Spectrometry (GC-MS) Lab In-House Method Acetate, Formate, Propionate, Lactate, Glycerate
WATER
Water Bottom Analysis Methods Method Identifier Determination of
Ion Chromatography (IC) for short chain fatty acids Modified EPA 300
Acetic, Formic, Propionic, Lactic Acids
IC Test for Free Glycerin Lab In-House Method Glycerin
Determination of Dissolved Alkali and Alkaline Earth Cations and Ammonium in Water and Wastewater by Ion Chromatography
ASTM D691919 Cations (Sodium, Calcium, Magnesium, Potassium, Ammonium) and Anions (Chloride, Sulfate, Nitrate and Fluoride)
pH (Electric) EPA 150.120 pH Conductance (Specific Conductance, umhos at 25°C) EPA 120.121 Conductivity Nonhalogenated Organics Using GC/FID SW846 8015B22 Ethanol and Methanol
FUEL
Vapor Analysis Methods Method Identifier Determination of
Ullage % Relative Humidity Hygrometer used per
manufacturer instructions
% relative humidity
Carboxylic Acids in Ambient Air Using GC-MS ALS Method 102 Acetic, Formic, Propionic, and Butyric Acids
Determination of Lactic Acid in Ambient Air
Modified NIOSH 7903 Lactic Acid
VAPOR
Assess and Categorize Corrosion Coverage
Based on protocol developed by CRC Diesel Performance Group – Corrosion Panel
3 assessments of coverage on STP shaft ◦ Minimal as < 5% ◦ Moderate from > 5% to < 50% ◦ Severe as > 50%
If in unanimous agreement, UST was categorized If not in agreement, discussed and considered overall condition of UST equipment and categorized by panel vote
Observed Corrosion Examples – Example Of An UST System with a Fiberglass Tank With Minimal Corrosion Coverage (Installed 2003 And Age Of Filter < 1 Month).
Example Of An UST System with a Fiberglass Tank With Severe Corrosion Coverage (Installed 1986)
Example Of An UST System with a Steel Tank With Minimal Corrosion Coverage Example (Installed 1994)
Example Of An UST System with a Steel Tank With Severe Corrosion Coverage (Installed 1992).
Observed Corrosion Examples –
More Corrosion Examples – STP Shafts
Drop Tubes
Tank Walls
Ball float cages
ATG floats/shafts
3 8 7 4
9 11
0
4
8
12
16
20
Minimal Moderate Severe
42 USTs by Corrosion Category and Material
Steel Fiberglass
Looking at the Data
Analyzed data according to corrosion category
Identify potential predictive characteristics
Identify any trends with respect to corrosion development
A note about findings: Please do not cite. This is preliminary data from the report which has not yet completed peer-review. This is presented only to share what we initially observed. Only the final peer-reviewed paper should be cited as an official source of information from the study.
Key Findings
Corrosion appears to be very common. 35 of 42 USTs judged as moderately or severely corroded.
Likely affecting same or higher proportion of total ULSD UST population
– emergency generators and owners of single UST systems were not represented in this sample.
Corrosion could pose a serious risk to integrity or functionality of metal UST system components.
No ‘smoking gun’ correlation among corroded tanks identified.
Gasoline found in all 42 samples, and ethanol in 38 of the samples.
Assumptions
Microbiologically influenced corrosion (MIC) likely responsible for the corrosion.
◦ Food sources (ethanol or glycerol) were present
◦ All water bottoms found acids that could result from microbial consumption of ethanol or glycerol
◦ Conditions good for microbial growth
Eliminating water is recognized as a key factor in preventing this corrosion.
From ASTM D975: X6 | MICROBIAL CONTAMINATION
X6.1 Uncontrolled microbial contamination in fuel systems can cause or contribute to a variety of problems, including increased corrosivity and decreased stability, filterability, and caloric value. Microbial processes in fuel systems can also cause or contribute to system damage.
X6.2 Because the microbes contributing to the problems listed in X6.1 are not necessarily present in the fuel itself, no microbial quality criterion for fuels is recommended. However, it is important that personnel responsible for fuel quality understand how uncontrolled microbial contamination can affect fuel quality.
X6.3 Guide D6469 provides personnel with limited microbiological background an understanding of the symptoms, occurrences, and consequences of microbial contamination. Guide D6469 also suggests means for detecting and controlling microbial contamination in fuels and fuel systems. Good housekeeping, especially keeping fuel dry, is critical.
Next steps Educate owners about the risks.
Use available treatments or preventions if your system is affected
Remove water, conduct testing, tank lining, oxygen displacement, biocides, corrosion inhibitors, others.
Explore changes to technical standards and operating procedures
Support continued research on causes and solutions
Thank You for Listening!
Ryan Haerer EPA Office of Underground Storage Tanks
[email protected] 703-347-0151
Thanks to:
Anne Marie Gregg, Battelle For her efforts on the study and materials for
this presentation.
[email protected] 614-424-7419
Please reach out to EPA to share input, ideas, information or with any questions.