Aluminum can make for a great fuel tank material, as long as the tank is designed and installed properly. Aluminum is self-repairing, if given the chance to dry. The two main causes of failure in aluminum tanks come from chafing and corrosion due constant exposure to moisture or moist objects. Tanks submitted to moisture and a lack of oxygen will quickly corrode. The key methods to prevent corrosion and damage are listed as follows.
Ensure the fuel tank is constructed from adequately thick material. This will depend on the size of the tank. The USCG lists corrosion as the cause of 92% of tank failures in the Boating Safety Circular 79, so we will focus on this issue.
Ensure the tank is installed above any bilge water expected to collect. Again, wetting the tank and preventing exposure to air will corrode the tank quickly.
Next, ensure the fuel tank is mounted on 1/4" strips of 3-4" wide neoprene or other non-vulcanized rubber. The strips should be mounted to the tank itself, and aligned with the tank's internal baffles. This will prevent physical damage, and eliminate any gaps water might collect in between rubber and tank surface. Straps across the tank should be avoided, as these may cause chaffing and entrap water.
Aluminum mounting flanges should be welded to the tank. The flanges should hold the tank in position, and stood off from nearby bulkheads or surfaces. The goal is to allow air circulation around the entirety of the tank, preventing crevice corrosion caused by moisture.
To prevent galvanic corrosion, all fittings in contact with the tank must be made of aluminum or 316 stainless steel. Copper will quickly corrode the tank and should never be used. Grounding and bonding requirements must also be followed.
Surrounding structures must be taken into consideration. The fuel tank must be mounted somewhere structurally capable of carrying its weight. The deck above must also have adequate reinforcement to prevent sagging onto and chaffing the tank top.
Regulations set by ABYC, ISO, and the USCG are always a good source to help guide your tank design and installation.
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