Fuel tank questions

[Sirocco]

For those of us who are restoring a older bike, oftentimes we find rust in the tank, a major problem in the restoration.
This got me thinking, why? An aluminum tank would not have this problem, and I remember my Ossa Pioneer having a fiberglass tank.

My guess is the manufacturer is saving a couple of pennies per tank, but creating a major headache for us.

[stinkwheel]

It's more than a few pennies difference to make an aluminium tank. They also aren't a panacea, the welds are finicky, the dent easily and they love to develop pinhole leaks. When I got an aftermarket trials tank for my bullet, it was roughly double the price to have it in aluminium rather than steel.

Fibreglass is cheap and light but it doesn't play well with ethanol fuel and at one point it wasn't road legal due to how easily it ruptures in a crash.

ABS plastic is a decent option, but it doesn't look nice and paint doesn't key to it well so you'd be wanting a cover for it if you were to be using a traditional design. Again, plastic tanks don't always play well with ethanol. Early 2000s KTM tanks swell to the point you can't get them off the frame and a lot of the Triumph ones have started becoming vapour porous and blistering the paint.

Galvanised steel seems like a good idea to me.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.