One of our most popular webinars from the past dealt with such an important issue - Diesel Fuel Storage Tank Corrosion - that we thought it was important to share it with our blog readers. Over the course of four articles, we will be sharing the content of that webinar here on the blog.
Table of Contents
You can read the first part of this series, Corrosion in Diesel Fuel Storage Tanks- The History of Corrosion, here. You can read the second part of the series, Corrosion in Diesel Fuel Storage Tanks- The EPA’s Methodology, here. You can read the third part of the series, Corrosion in Diesel Fuel Storage Tanks - The Results, here.
Even if your UST system seems fine, hidden dangers could be lurking. The EPA has found that 75% of tanks surveyed showed no visible signs of corrosion, yet over 80% of those still had signs of moderate to severe corrosion inside. This discrepancy highlights a critical gap in tank maintenance awareness. What to do about this? Visual inspections can do a long way.
Whether your tanks are fiberglass or steel, regular visual inspections are a non-negotiable part of their care. Think of it like monitoring your blood pressure: you might feel fine, but unseen issues could lead to major problems. What's true of your cardiovascular system can also be true of your fuel storage system.
Inspecting Filters: Look for sludge or particle accumulation. Debris that resembles coffee grounds or fine black grit often indicates internal steel corrosion or MIC activity, and reddish or orange particulates point to active rust shedding from tank walls or fittings. Slime-like residue can signal microbial biomass breaking loose from the water–fuel interface. Any pattern of accelerated filter plugging, especially with these materials, is an early warning that the tank interior is degrading and needs further investigation.
Checking Tank Interiors: Don't wait for evident symptoms. Early corrosion rarely shows up as dramatic rust or holes; more often it starts as subtle pitting near the tank bottom where separated water collects, slight discoloration or roughened “sandpaper” textures on metal surfaces, or small blisters and pinholes in interior coatings. Inspect welds, seams, drop tubes, manways, and any area where moisture or sludge can settle, because corrosion often hides underneath microbial sludge layers long before it becomes visible. Look for early warning signs such as unexpected fuel filter plugging with black or rust-colored debris, hazy or layered fuel samples, recurring water in the tank after removal, or a sour sulfur-like odor indicating microbial activity. Even minor changes like these can signal active corrosion cells developing well before alarms or obvious symptoms appear.
If anything, one of the critical takeaways here is that you should establish a routine inspection schedule. For most facilities, filters should be inspected at least once a month, with more frequent checks—every one to two weeks—during seasons with high humidity, significant temperature swings, or when the site has a history of water intrusion or microbial activity. Any time a system experiences unexpected pressure drops, slow fueling, or alarms, the filters should be checked immediately. Regular, documented inspections help catch corrosion, sludge formation, and microbial growth well before they escalate into system-wide failures.
The EPA stresses the importance of regularly checking for and removing water from USTs to prevent corrosion. Surprisingly, many tank owners and operators neglect this crucial maintenance step. This oversight is especially common in tanks not used frequently or those outside stringent regulatory oversight, like emergency fuel storage tanks.
Tanks that sit unchecked for years, such as some diesel fuel storage tanks, are highly susceptible to corrosion-related problems. This can lead to significant safety risks and costly repairs.
Utilize Water Monitors: While many systems have water monitors, they should not be your only line of defense. These devices can fail or give inaccurate readings.
Human Inspection is Key: Regular physical inspections by trained personnel are irreplaceable. They not only confirm the readings from electronic monitors but also provide a more comprehensive understanding of the tank's condition. And it can be as simple as sticking a tank with water paste.
Act Proactively: Regularly scheduled checks are essential, even for tanks that are rarely used. Don't wait for visible signs of corrosion or system failure - by then, it might be too late.
If water is detected during an inspection, immediate steps should be taken to remove it. This not only prevents corrosion but also helps maintain the overall health and efficiency of the fuel system.
Remember, consistent and thorough monitoring for water in your UST system is not just a best practice — it's a necessity for the longevity and safety of your storage tanks. Proactive measures today can save significant costs and prevent hazardous situations in the future.
To safeguard against tank corrosion, the EPA strongly advises that tank operators filter fuel for water and particulates, either before delivery into the UST or shortly after when recirculating the stored fuel.
Filtering fuel, as emphasized by the EPA, is not just a recommendation but a necessity for the longevity and safety of your UST. Implementing this practice can significantly reduce the risk of costly repairs and environmental hazards in the future.
Owners should contact UST servicing companies to further evaluate extent of corrosion in their system, if they find corrosion or if they suspect it’s there. They should not hesitate to partner with service companies.
The EPA recommends this because they know that few tank owners/operators have the technical knowledge or resources to fix their own tanks or to more fully evaluate the extent of corrosion problems and damage in their tanks if preliminary signs manifest themselves.
UST-service companies are experts in their field, and solving corrosion issues in tanks should be more in their wheelhouse than a tank operator.
What the EPA doesn’t want to have happen is for tank owners to suspect they have a corrosion problem in their tank, but put off doing something about it because they don’t feel they have the resources or knowledge to solve it. Remember, the EPA undertook this because they recognized that corrosion damage and worst-case scenarios for fuel leaks into the environment had serious potential consequences for both environmental health and human health. They do not want tank owners to put off fixing a problem.
Action item #5 from the EPA piggybacks onto what we were just talking about. If corrosion damage or its symptoms are found, the affected equipment should be repaired or replaced. And again, remember that a big reason why the EPA looked more closely at this issue was the potential for damaging releases into the environment.
The leak detection equipment in a UST was what the EPA was most concerned about. So, if that, or any other part of the UST, is found to be damaged by corrosion, they have to be repaired or replaced.
So far, the EPA’s recommendations have covered monitoring tank and fuel condition (both stored and incoming), housekeeping measures for contaminants, and the need for not putting off essential repairs.
The sixth and final recommendation addresses simple preventive measures that may be easily done by tank owners and operators themselves. These are the use of both biocides (to kill existing colonies and prevent future MIC) and liquid corrosion inhibitor additives – what the EPA terms “filming amines”.
Why did the EPA specifically call these two treatments out? Because they directly address the problems that tank corrosion is associated with.
Given the link between storage tank corrosion and microbial activity, it stands to reason that the EPA would recommend tank operators incorporate something into their housekeeping that most directly controls microbial growth.
Biocides are the only chemical treatment that kills active microbes. So, using them brings both a remedial and a preventive benefit.
So, if a tank has microbially induced corrosion, it also has an existing microbial presence. Treating it with a biocide is the first essential step to killing the microbes, which is the only way to stop MIC from progressing. That’s the remedial benefit.
This concept – the essential use of biocides as the most effective weapon against the biggest causal contributor to storage tank corrosion – this is a departure from the traditional rule of thumb the industry had held for years. If you kept the water under control, you wouldn’t have microbe problems.
But as they started seeing around 2007, even though they were doing the same things they always did, they were now having corrosion problems they didn’t have before. This was most likely due to the new ULSD fuels and their lack of resistance to microbes (because of low sulfur presence).
Now, it’s clear that water control isn’t enough. Extra measures must be taken. And that means using biocides, as the EPA recommends.
There’s a lot that may be said about selecting which biocide to use, probably a topic that’s worth a whole another webinar in and of itself. Suffice it to say that not all biocides are the same. They use different chemistries (isothiazolone, boranate, thiocyanate, dibam/nibam), and some work better than others in certain situations.
At the risk of over-generalizing, the best biocides will score well in these main areas:
So, it’s important to make a good biocide choice. If you’re going to take the time and the money to follow the EPA’s recommendation in this manner, you want to make sure you select the right one for you.
Some of the popular biocide trade names, you might have heard of – Bellicide, Biobor, and Kathon. There are differences between them. If you’re not sure, talk to us about it.
Their other recommendation is the regular use of protective chemical agents that protect tank surfaces from damage.
Liquid corrosion inhibitors are added to the fuel in the tank, typically at very low treat rates between 1:10000 and 1:20000. They use a “filming amine” chemistry to lay down a protective film onto whatever surfaces the treated fuel comes in contact with. This film protects the surface from corrosion as long as the fuel is in contact.
Better liquid corrosion inhibitors also provide other benefits in addition, to increasing their value. They can also function as sludge dispersants and biomass dispersants. So in addition to protecting surfaces from corrosion, they also solubilize tank sludge and dissolve it into the fuel, which cleans the system over time. They can also improve the effectiveness of biocides when used alongside them because they break up and disperse biomass formations in the tank that otherwise would shield microbes from biocide presence.
Bell Performance has one such formulation – Tank Treatment SDF, that provides all of these benefits – protecting surfaces from corrosion and dispersing sludge and biomass.
One final note - there is a biocide chemistry, commonly known as MBO, that combines being a biocide and a corrosion inhibitor. ClearKill is one trade name for it, while if you were in Europe, you could find it sold under the trade name Grotamar. It is a worthwhile biocide to consider if you're aiming to follow the EPA's best practice recommendations here.
To wrap things up, we would be remiss in not mentioning that these essential chemical recommendations – use of biocides and corrosion inhibitors – won’t work optimally if they are not applied properly. Their effectiveness hinges on correct application. It’s not as simple as just adding these chemicals to your fuel tank; they need to be properly distributed to be effective. Let's break this down:
Many entities hesitate to incorporate these practices due to perceived complexity, lack of time, or resources. However, neglecting these steps can compromise your fuel integrity.
Consider partnering with a specialized service provider who can:
A suitable partner goes beyond basic tank servicing or fuel polishing. Look for providers offering a holistic approach, encompassing both mechanical cleaning and chemical treatment, as recommended by the EPA.
Proper chemical treatment is not a luxury but a necessity for maintaining fuel integrity. By understanding the importance of correct application and considering the support of specialized service partners, you can ensure your fuel storage system remains in optimal condition.
A good service partner should, essentially, be able to provide a turn-key service – handling all of these important elements – chemical treatment, mechanical fuel processing and tank cleaning, and diagnostic testing. And if you or another company doesn’t need all of these, they should be able to break out only what you need.
And that’s essentially the kind of service we offer with the Bell FTS program. Lots of people with stored fuel know the importance of these best practice recommendations. But it’s easier and more cost-effective for them to let a comprehensive service partner handle it for them. That’s what the Bell Fuel & Tank Services arm does. We cover all the bases, whatever is needed, and typically it’s more cost-effective for Bell FTS to handle it than it is for them to do it themselves.
Normally we like to do a brief review of what we’ve covered in webinars like this. We will also make this available as a link with audio in case you missed anything that you want to refresh your memory on.
The important points:
Click here to read the first part of the webinar transcript: Corrosion in Diesel Fuel Storage Tanks- The History of Corrosion
Click here to read the second part of the webinar transcript: Corrosion in Diesel Fuel Storage Tanks- The EPA’s Methodology
Click here to read the third part of the webinar transcript: Corrosion in Diesel Fuel Storage Tanks - The Results