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Written by Bill Orr (Felix Marine Industries)
Published in Nor’wesing Magazine Dec 5, 2007
Are you concerned with the possibility of corrosion inside your fuel tank? Does the subject seem confusing? Well, you’re not alone, In fact, no one understands these conditions fully, but I hope to clarify some of the causes and identify some solutions.
Boaters can avoid leaks and increase the life of their fuel tanks, prevent costly repairs, and environmental accidents with proper maintenance.
The problems begin with the reality that in most pleasure boats the fuel tanks are a long-term storage facility. Today, diesel and bio-diesel products are inherently unstable and begin to break down within 90 days of delivery. Modern diesel fuel is produced differently from the days when companies relied on a more stable distillation process. Fuel oils are now catalytically cracked and rely on manipulation of hydrocarbons. The fuels delivered today are a blend of both processes.
Most common fuel leaks are due to the corrosive effects of sludge, microbial growth, water, and sulfur. The combination of these products make a deadly cocktail that will eat holes through your tank bottom. Tank sludge will trap water in pockets and react with sulfur in the fuel. The new low sulfur fuels are more corrosive than the past high sulfur fuels.
If your tanks are cold steel, aluminum, or stainless, they are subject to corrosion. Interestingly, when we are doing fuel tank repairs at Felix Marine Industries we find that in half of the cases the welds are first to show major corrosive effects.
Solutions include taking action before you have a problem. Replace fuel filters every six moths. Do your filters show a black or brown sludge? This will tell you if the fuel is breaking down. If there is a dark jelly substance on the filter this is an indication of yeast, fungi, bacteria or mold and will rapidly deteriorate the quality of fuel. Is there water in your Racor bowls? Water and oxygen are the building blocks, along with diesel which is an organic fluid. An interesting point is that the term used for the growth in your tank is algae. The term is a misnomer because algae will not live in a fuel tank.
There are dozens of fuel additives on the market and we don’t recommend a particular one, but look for a product with a surfactant that will emulsify standing water into the fuel. A corrosion inhibiter to deal with today’s low sulfur fuel is preferable. Fuel catalysts can clean some undefined contaminated fuel systems. A catalyst will dissolve sludge and allow it to burn through the combustion chambers along with water that has been emulsified. Many boaters use Biobor JF. This product is a pesticide that will kill microbial growth, but it will not remove the skeletal remains of what was killed. It will not provide the protection your tanks and engine deserve. It does one thing very well. It kills microbial life in hydrocarbon fuels.
Now that we have considered the subject of preserving the tank bottom, let’s view the exterior of the tank. Salt water will promote rust on the exterior and tank top very effectively. Is the fill or decking allowing water to accumulate on the tank top? Is the shaft throwing water on the tank as the engine turns? Rust damage and leaks on the top of a fuel tank are generally difficult to repair due to lack of access through decking.
When you are providing the proper care of your fuel tanks, you are also providing a valuable service to the engine. Clean fuel provides peak engine performance. It improves combustion while protecting your injectors, pumps, and motor.
Replacement of fuel tanks in pleasure boats is rarely an easy chore due to the way most boats are constructed. The tanks are installed, and then everything else is built on top and around them. Contaminated fuel leads to poor engine performance, premature engine failure, shortened duty cycles, unplanned downtime, and expensive repairs. Early failure of injection pumps and injectors due to the abrasive and corrosive nature of these contaminants compounds the expense.
At Felix Marine Industries, depending on the size and configuration, we use suction wands to remove the residue from tank bottoms. When tanks are baffled, it is often necessary to install removable hatches to access all compartments in the tank in order to fully remove al the contaminants. If the tank has been leaking, we steam clean the tank and repair the leaking seam or pitted bottom with different methods (according to the material of the tank). This process of fuel polishing, tank cleaning, and repair is an unwelcome expense to boaters, but the alternatives are many times more costly.
In addition to the machinery costs, consider the price of safety of the boat owners family, our environment, and the boat. Engine shut down in turbulent waters when the bottom “Sludge Bugs” are stirred up and plug filter, can be a life threatening event. (Unless you’re a sailor of course.