On Wed, 27 Aug 2003 19:33:14 +0100, "Peter Crosland"
wrote:

Domestic oil tanks are frequently found
to be rusting from the inside as well as externally.

I've never seen one.

As it happens, I've looked. I've collected a large number of these
things, as part of a passive solar project (this is also how I know
that bitumen-based paints can be a problem when you locate the tanks
in a greenhouse)

If water condensate settles out in an oil tank, it's under a layer of
oil in a saturated solution with iron salts. There's minimal oxygen in
there, and it's in its own little brew of DIY Fernox. Despite being
given most of these tanks on the basis of them "having rusted out",
then carefully ultrasounding the bases and preparing to weld the
things secure again, I didn't find _one_ of these things with
significant corrosion from the inside.

Where I did see damage was where water was trapped _outside_ the tank,
where a cuboid tank was rested directly on a brick pier. This is just
bad installation practice, and the sort of thing you should check when
painting.

IMHO, domestic oil tanks just aren't in any hurry to rust out from the
inside. Counter-examples welcome.