Haven't heard of any fuel tank
problems. Those are stainless steel
(at least on my boat).
There have been problems with some of the aluminum
tanks due to chlorine in the water reacting with the metal. Not really welds failing, just corrosion
, which tends to produce pinhole leaks
if it's allowed to go unchecked.
Most complaints were about aluminum chloride crystals clogging up the water pump strainer or faucet aerators. Using a carbon canister filter on "city" water (the chlorinated kind), solves the problem easily. I have the aluminum water and holding tanks on my boat and after I figured out the chlorine thing, never had any issues.
I understand the newer IPs are being fitted with fiberglass
water and holding tanks.