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Corrosion in Diesel Fuel Storage Tanks- Recommendations for Tank Owners

Posted by: Erik Bjornstad

The first Bell Performance webinar of 2017 dealt with such an important issue that we thought it was important to share it with our blog readers. Over the course of 4 articles, we will be sharing the content of that webinar here on the blog.


diesel fuel storage tank cleaningYou 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.

Recommendation #1: Visual inspections of filter and inside of UST systems

Recommendation #1 - Owners should conduct visual inspections of filters and the inside of UST systems, even if they haven’t seen any symptoms. And doesn’t matter if the tanks are fiberglass or steel. Why? Severe corrosion may already be established before symptoms appear.

The EPA offers this recommendation in part because of the fact that the study showed that 75% of tanks had shown no previous evidence of corrosion damage that the owners knew of. That was balanced against the coordinating fact that over 80% of tanks had at least moderate corrosion going on.  Balance those two figures against each other and we can see there’s a tremendous gap between what’s happening in storage tanks and what their owner/operators think is happening.

This is why it’s important to visually check your fuel storage systems at some kind of interval. The absence of apparent problems and symptoms is not an indicator that the tank owner is home free.   Just like checking your blood pressure. You may feel fine, but if you have hypertension, you won’t really feel it until you have a serious problem. It’s recommended to check your blood pressure at regular intervals, even if you feel fine.

If they check their filters, they may find Sludge and particles inside filters that may look like coffee grounds. This is a direct sign that there’s corrosive damage going on in the storage tank.

#2: Monitor and remove any water present in the UST

They should monitor for and remove any water present in the UST.

REGULARLY CHECKING FOR AND REMOVING WATER BOTTOMS is a critical preventive method for reducing the risk of corrosion (in the words of the EPA).  This is the one that tank owners are probably most aware of; at least you would think so. But there’s a surprising number of owners and operators who don’t regularly monitor and control water levels.

Many systems are fitted with water monitors that read and report water levels. And those are great. But you should never rely solely on those. There’s no substitute for simple human sensory checking, even if it’s just to confirm that your water monitoring equipment is functioning properly.

This lack of housekeeping is most common with emergency fuel storage tanks that don’t get used very often, tanks that don’t fall under a regulatory mandate to monitor their health.  Think about all those diesel fuel storage tanks that sit for years without being checked on. You can almost guarantee that those tanks are going to see problems

Recommendation #3: Fuel should be filtered for water/particulate before it is delivered into the UST

Action Item #3 – The EPA recommends that tank operators should filter fuel for water and particulate BEFORE it is delivered into the UST. Either that, or they can recirculate and filter for water and particulates after the fuel has been dropped and stored.

In its study, the EPA saw clear evidence that water and particulate content in fuel was the strongest correlator with tank condition and corrosion.  And there are a couple of considerations underlying this recommendation.

First, even if you keep your fuel in peak condition, that doesn’t mean everyone else does. When you get a fuel drop, you’re relying on the supplier to deliver fuel product that’s in as good condition as yours.

Second, filtering the fuel as recommended ensures that you’re removing any precursors or contributing agents that can accelerate both fuel instability and tank corrosion. Especially water.

Filtering the fuel before or after it’s been dropped was important enough for the EPA to specifically make the recommendation.

Recommendation #4: Partner with UST-servicing companies to further evaluate corrosion problems

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 owner/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.

Recommendation #5: Repair or replace equipment if corrosion is found

Action item #5 from the EPA piggybacks onto what we were just talking about. Obviously, if corrosion damage or its symptoms is 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.

Recommendation #6: Use of biocides and liquid corrosion inhibitor additives

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.

EPA Recommendation - Use of Biocides

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.

The preventive benefit comes from interval treatment of fuel storage tanks with low levels of biocide – typically around a 1:10000 treat ratio. This is proven to be the best way to prevent microbial presence from getting established in storage tanks.

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. And 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:

  • Kill speed – they should be able to work fast.
  • Kill length – the most important one. This is the amount of time the biocide will maintain a 100% kill rate in the fuel.  4 weeks is going to be about the best you’re going to get. That doesn’t mean microbes all come back after 4 weeks + 1 day. But some popular biocides only last 1-2 weeks, and that’s a significant difference.
  • Effectiveness in fuel and water – this relates to the fact that a better biocide will start out in the fuel phase and will migrate or partition into the water phase. This is essential because the process of moving across the interface will kill microbes in that important area. Some popular biocides like Biobor become deactivated when they hit the water phase, making them less effective. Biobor actually cut its teeth on use in jet fuel, which by definition has to be virtually water free.
  • Impervious to pH – some biocide chemistries become less effective in acidic environments. This is a problem because fuels that are more acidic will be more likely to have serious microbial problems. They became acidic because of the low MW acids produced by the microbes.

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, Kathon. There are differences between them. If you’re not sure, talk to us about it.

EPA Recommendation – Liquid Corrosion Inhibitors

Their other recommendation is 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, 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. And 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, dispersing sludge and biomass.

Proper Application Is Key for Best Results

To wrap things up, we would be remiss in not mentioning that these essential chemical recommendations – use of biocides and corrosion inhibitors – they won’t work optimally if they are not applied properly.

That’s not to say they’re terribly complicated to apply, but it’s more than just dumping a gallon of biocide in the top of a fuel tank and letting it sit there.  Chemical treatments like these only work if they come into contact with their targets. Biocides can only kill the microbes they get to (hence why biomass formations can interfere with their effectiveness). Sludge dispersants and corrosion inhibitors only work if they come into contact with sludge and tank surfaces.

The ideal way to apply these recommended treatments is either by direct injection or addition to the fuel along with fuel circulation. More people have the ability to do the latter, but it’s a little more involved than just having a crew member dump in a bottle of treatment and leave it.

And this can make some entities shy away from doing what’s best for their stored fuel.  They may not feel like they have the time, the manpower, or even the willingness to add something additional to their plate.

This is where looking at service partners can be a benefit. A good service partner here can take all of this off the plate of a busy company, handling the fuel maintenance and service. They should also be able to do tank cleaning and fuel filtration, and back all of this with diagnostic testing that shows the benefits of what they’ve done.

This kind of service partner is different from just a tank service company or a fuel polisher. Tank service companies are good at repairing and replacing tank parts, but rarely delve into the service of the fuel itself.  Fuel polishers aren’t difficult to find, and they mechanically clean fuel, but that’s only part of what you would need – they typically leave out the chemical treatment (which is what the EPA recommended in the first place).

Bell Fuel & Tank Services

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 didn’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.

What Did We Learn Today?

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:

  • Due to an increased incidence of problematic corrosion, the EPA tank corrosion study – the largest to date on the topic with over 40 tanks comprehensively studied.
  • More than 80% of the tank showed significant signs of corrosion damage.  And this was true despite most of those tanks still receiving the same maintenance as they did before. So, it wasn’t like they were just being left there.
  • Most of the owners of these tanks didn’t know they had problems or hadn’t seen any signs yet.
  • Didn’t matter if it was metal or fiberglass tanks.
  • EPA recommends controlling water in tanks, filtering the fuel for water and particulate, using biocide and anti-corrosion chemical treatments, and partnering with service companies to make sure tank damage is properly repaired. And it can also be helpful to partner with a service company like Bell FTS to ensure the fuel is properly treated, to take that out of your hands so you can concentrate on doing business better.

Missed Part of the Story? Catch Up Here

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

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This post was published on March 23, 2017 and was updated on March 31, 2017.

Topics: Diesel, Fuel Storage, Fuel and Tank Services