The inside of a fuel tank

[skipmac]

Do you know what's going on inside your old boat's diesel tanks?

Well I found damp spots of diesel under my tanks so pulled them for inspection and found pinhole leaks in both. I cut out the bad spots and took a couple of photos. First cleaned and polished with fine grit sandpaper to show the damage.

One with a 1 inch ruler for scale. The ones with the bright spots are with a light below the metal shinning through the holes.

You can see how the aluminum was eaten through by the acids in the diesel sludge. The tanks are 1984, 5052 alloy, about 1/8" thick. The PO who owned the boat since new, swore he kept biocide in the tanks always, but when I got the boat I sucked out a pint or more of water and sludge from each of the two tanks. Obviously he never drained the tanks or polished the fuel in them.

By the way, I did inspect the tanks through a small port in the top but the corrosion was not visible in the staining and deposits on the inside of the tanks.