Aluminum versus stainless steel fuel tanks

[Bowdrie]

Originally Posted by Manateeman

When TIG welding stainless, the gas coverage is critical. You need it on BOTH sides of the weld. We see a lot of welders try to ignore this usually because nobody looks at the interior. Lots of other reasons for bad welds, but this is a classic.

True enough, problems with SS tanks for diesel invariably involve the welds, particularly at corner joints.
In the grand scheme the use of SS for diesel is a fairly new development and their has been a learning curve of both technique and filler rod alloys.
The old Monel tanks gave such good service because of the very high Nickle content, and with rivets and solder their was never enough heat applied from welding to compromise the base metal.
In one respect today's fuel itself can give a SS tank a longer life.
It's the Sulphur content.
In the presence of water the sulphur would form sulphuric acid and the change of state of the SS at the welds was highly susceptible to attack.
With the low/ultra low sulphur content of today's fuel that issue has been markedly reduced, (the same can be said for aluminum,) but not totally eliminated.
Outside of some exotic metals, for ultimate longevity an epoxy/fiberglass tank is hard to beat, and can be patched/repaired, or connections changed without specialized equipment.

[Manateeman]

OH how the manatee crew loves monel. Let us count the ways.
If you have an aluminum tank that might sit in a dark and damp place, you can cover the exterior with glass in epoxy. Proper prep.
We did this with two small tanks but unfortunately none of the manatee crew will remember to pull them out and inspect the results fifty years from now.
Captain Mark

[JPA Cate]

We had an aluminum fuel tank, that, over time, had enough condensate in the outboard forward corner (lowest spot), eventually pitted through. The bush repair was part of an aluminum beer can, cut and formed to shape, epoxied over the area. Some years later, the boat was sold, and the tank was still not leaking at the time of sale.

Ann

[svfinlandia]

Originally Posted by JPA Cate

We had an aluminum fuel tank, that, over time, had enough condensate in the outboard forward corner (lowest spot), eventually pitted through. The bush repair was part of an aluminum beer can, cut and formed to shape, epoxied over the area. Some years later, the boat was sold, and the tank was still not leaking at the time of sale.

Ann

And I bet the surveyor did not find the beer can.

Al, S/V Finlandia