What precaution must be taken when installing a brass fitting into an aluminum fuel tank?

When installing a brass fitting into an aluminum fuel tank, it is crucial to isolate non-galvanically compatible materials with a 300 series stainless steel bushing because of the potential for galvanic corrosion. Brass and aluminum are dissimilar metals that, when in electrical contact in the presence of an electrolyte (like fuel or moisture), can create a galvanic cell. This results in accelerated corrosion of one of the metals, typically aluminum, which can lead to failure of the fuel tank.

By inserting a 300 series stainless steel bushing between the brass fitting and the aluminum tank, you effectively create a barrier that prevents direct electrical contact between the two metal types. This precaution helps mitigate the risk of galvanic corrosion and prolongs the lifespan and integrity of the aluminum tank.

Other options, such as using Teflon tape on threads or ensuring material compatibility, do not adequately address the specific issue of galvanic corrosion, which is critical in this context. Avoiding brass fittings altogether is also an extreme measure that eliminates the utility of brass in applications where it may be appropriate, as isolation through a bushing is a more effective and practical solution.