Plastic Vs Aluminum Marine Fuel Tanks

Plastic Vs Aluminum Marine Fuel Tanks

If you're in the market for a new boat or need to rebuild your present boat's fuel system, it's worth paying attention to your fuel tanks and, more precisely, the material they are made of. The four primary materials used in marine fuel tanks are:

  • Polyethylene
  • Aluminum
  • Fiberglass
  • Stainless steel

Fiberglass and stainless steel fuel tanks are less prevalent. We will be focusing on polyethylene and aluminum marine fuel tanks in this blog.  

Aluminum Marine Fuel Tanks:

Aluminum tanks are a far more versatile alternative to polyethylene. Aluminum is an excellent material for fuel tanks since it can be rolled and bent into obscure shapes. Because aluminum tanks are custom-built, finding one to match the style of your boat is straightforward. 

While one must screw metal fasteners (hose tails, etc.) into plastic tanks, such fittings can be welded directly to the tank in the case of aluminum tanks. A customized marine aluminum fuel tank can use various spaces to increase fuel capacity. 

Plastic gasoline tanks are also weaker and more susceptible to punctures than aluminum fuel tanks; Aluminum is more prone to denting and can withstand more stress. While aluminum is soft for a metal, it is significantly more resistant to damage and, more importantly, leakage than polyethylene. While a damaged tank is inconvenient, it will not cause as much damage as a tank that spills all over your boat. Aluminum for the win! 

Installing an Aluminum Fuel Tank

When building an aluminum tank, the most crucial aspect is reducing the risk of crevice corrosion. 

Crevice corrosion occurs when water gets trapped between the tank and another surface, such as the tank support structure. Water rarely causes corrosion because the oxygen in the air forms an oxide layer that protects the aluminum from oxidation. However, when water is trapped in a fissure, the aluminum surface is deprived of oxygen, leaving it vulnerable to corrosion. 

There are several methods for preventing crevice corrosion; however, the following are the most important: 

  • Avoid bringing porous materials (most notably wood) into contact with the tanks. If there is a direct channel of contact, wooden stringers, for example, could soak up water from the bilge that eventually makes touch with the tanks.¬†
  • Installing intermediate strips of plastic (such as acetal or Delrin) between the tank and the wooden support framework will act as a moisture barrier.¬†
  • The tanks should be kept away from the bulge so that they do not constantly encounter bilge water.¬†

Fully laden fuel tanks are incredibly hefty, so they must be supported appropriately. Longitudinal supports are required to avoid sagging along the tank's length, and the same is true in the transverse direction if the tank is wide. Remember that sagging can cause strains to form in the aluminum, which can lead to stress fractures. It's critical to keep this danger to a minimum!

Polyethylene Tanks

HDPE (High-Density Polyethelene) tanks are available in both conventional and custom variants: Blow-molded (produced in the same way as a plastic drink bottle) or roto-molded (like a canoe or kayak) are the most common.

Because off-the-shelf tanks are essentially more enormous jerry cans, they lack internal baffles to avoid violent 'sloshing' and vessel instability. On the other hand, custom HDPE tanks are built in the same way as aluminum, with plastic welding techniques used to achieve more complex geometry than standard tanks. This method also allows for the incorporation of baffles into the design. 

The permeability of HDPE, like most polymers, is a severe disadvantage. Diesel gasoline will seep into the plastic over time, potentially releasing fuel vapors and posing a fire hazard. While plastic may be easily molded into various shapes, there is a limit to how broad a plastic can be without losing structural integrity, at least without the use of baffles. 

Plastic tanks have a maximum capacity of roughly 1700 gallons (6500 liters) without any additional internal structure. Baffles can be utilized to offer additional stiffness and decrease movement of the fuel inside, or numerous smaller tanks might be used instead.

Why Nextwave Marine?

Clients nationwide choose us with over 20 years of experience because of our attention to detail and unparalleled customer service. Whether it's for a boat, a restaurant, or your property - if it's aluminum, we can build it! We specialize in building the highest quality aluminum outboard motor brackets, aluminum fuel tanks, and custom aluminum jobs to meet our clients' needs. Give us a call today at (305)699-4090) or shoot us an email at 

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