In article , John AS-
writes
In the REAL world a metal tank which is corroding through starts to give
signs long before serious leakage occurs. Over a pretty lengthy period you
will notice a smell of fuel around the tank then a damp patch will show
around the leak, followed over a month or several by an odd drip from the
locality of the corrosion and this will slowly progress.
When the damp patch appears its time to arrange to run it down and get a
new one installed.

My in-laws tank corroded at the back which they couldn't get to (bad
siting but out of the way) subsequently they lost 3/4 of a tank. I
suspect many metal tanks are only maintained on the bits you can see

Metal tanks do have advantages over plastic ones such as vandals can't
readily damage them, they can be sited on two simple plinth walls as
support and can be painted to suit your desires.
Plastic don't rot or rust but can and do split on their seams if under
stress, need a full flat base and vandals can pierce them or light fires
under them with spectacular results.

They don't all need a full flat base John, some of them have support
ribs that can be supported on plinth walls
I haven't heard of them being vandalised, it can't be all that common??

In answer to the OP its a good idea if possible to run the tank down to
nearly empty so it can be moved, shift away from the wall, wire brush the
seams and corroded spots and paint with decent primer and a couple of coats
of gloss (Buckingham Green is the reccomended colour but its your tank).
This assumes that the tank hasn't been allowed to get so bad that wire
brushing will destroy it of course)

I must admit having maintained a metal tank for a few years it was a joy
to get a plastic one
--
David