It all starts when a technician notices a few drips of fuel coming from a vehicle’s tank. Typically, the search for the source of the leak begins by looking for the obvious: a loose or defective hose or fitting. When that inspection yields no results, the next thing is to determine if the tank was hit by an object that could have caused a small puncture.
Often, this inspection reveals something much worse: the tank is corroding. Fleets across the country are discovering that corrosion is a main culprit for fuel leakage.
To make matters worse, a close examination will have to be made to determine if the corrosion is on the interior or exterior of the tank. In either case, this is a serious problem.
It’s well known that corrosion is already a problem on brake lines, electrical connectors, frames, springs and just about every component exposed to salts used to de-ice roads. However, few fleets consider tank or fuel system corrosion, which can occur on both steel and plastic products.
SOME BASICS
Let’s start out with some basics:
- Corrosion – This is the process of metal being destroyed by a chemical action.
- Delamination – This is a mode of failure for composite materials.
A significant contributor to these conditions can be traced to the changes in fuel resulting from both the Renewable Fuel Standard and Energy Independence and the Security Act of 2007 which mandated significant changes in fuel. The most agreeable cause is the increased acetic acid in fuel produced by microbes which produce aggressive action on components.
INTERIOR TANK CORROSION
The biggest culprit for interior tank corrosion is pitting corrosion – a localized form of corrosion wherein cavities (small holes) are produced in a material. Pitting is considered to be more dangerous than uniform corrosion damage because it is more difficult to detect, predict and design against.
Pitting corrosion is often found where there are high degrees of sludge in fuel filters with Ultra Low Sulfur Diesel (USLD) and metal tanks. Pitting occurs when water, fuel and bacteria combine to create sludge. Water and associated acids will get trapped behind the sludge and form the perfect habitat for pitting corrosion.
If you suspect internal fuel system corrosion, a good place to start is to cut open your fuel filters. If you observe debris that looks a lot like black coffee grinds or find rust chips the size of your fingernail, then you most likely have corrosion problems somewhere in your system.
TREATMENT OPTIONS
One treatment for internal fuel tank and system corrosion is the use of additives. While there are many additives on the market, these products typically fall into three categories.
Water Burners or Removers. Water is the key component in creating corrosive sludge. These types of products claim to burn off or consume water during combustion, or they use solvents, such as alcohol, to absorb it. Be aware that products that contain forms of alcohol:
- Can have difficulty removing large amounts of free (clear) water.
- Are often good “food” for bacteria and other troublesome microorganisms.
- Can cause swelling and breakdown of gasket and seal materials.
- Because sludge-producing bacteria is found in all fuel systems, one solution for reducing corrosion is to kill acid-causing bacteria with biocides. Unfortunately, if there is any water present in the tank, biocides become totally ineffective.
The reason: Even if a minute amount of sludge begins to develop, it forms a defensive barrier that allows the bacteria to continue to grow and produce more sludge where biocides can’t touch them.
Even if a biocide is used, and culture tests reveal bacteria levels being lowered as more product is added, corrosion-producing sludge is still being produced.
Filming Amines. These products work by placing a thin microscopic film throughout the entire fuel delivery system that both breaks up existing sludge and prevents new sludge, thus stopping corrosion. The technology does not claim to kill any microbes, but rather keeps the sludge and slime-forming bacteria from sticking to fuel tank components.
This technology also breaks up sludge so small it passes harmlessly through the filters and out the back to the engine.
SUMMARY
For fleets that discover fuel tank leaks that are not attributed to loose hoses or fittings or punctures, it is wise to take a serious look into ensuring that fuel systems are free from internal corrosion. This could be done through internal staff or hiring contractors, but be sure they are experienced and have the proper credentials.
Simply cleaning the tank or polishing the fuel – a process used to remove or filter microbial contamination from fuel in storage – will not address the root problem. There must be a proactive program to stop the corrosion problem before it becomes a maintenance and environmental issue.
Dan Jenkins is a principal with Iron Ox (www.theironox.com), a distributor of corrosion control products for fleets. He has more than 10 years of field experience assisting the fuel industry in solving issues with exterior and interior corrosion issues.
