We did this work
couple of times, actually two of the aluminum fuel tanks
of my Nauthitec 46 have been corroded and started leaking and we had to change both of them. Unfortunately most idiot manufacturers install the tanks
in the bilge
when the boat
is wide open and you cannot take them out later in one piece. We had to cut the galley
carefully and after taking out the tanks and replacing with the new ones, we installed and sealed the buttom of the galley
. It's barely visible..
Welding the fuel tank
can be very dangereous and difficult. Moreover, if you have the pitting corrosion
(which was our case) you have plenty of small holes and you cannot repair
by welding. I know there are some chemicals to block the holes and we never tried. All will depend on what kind of holes you have, in which part of the tank and how accessable these areas from the top. Again most of the manufacturers don't even put a manhole to have acces to it. Leave alone the welding, you cannot even see inside and clean it if necessary..