Water etc. tanks can be remediated with special 'lining' epoxies. For
water tankage you really should consider an epoxy that meets NSF or FDA
regs. for compatability to 'potable' water .... so you dont wind up
drinking a lot of toxic 'leachables'.
The Commercial Marine Industry uses 'lining epoxies' from Interlux
Commercial Division. For small quantities for potable water tank
lining, I use: www.epoxyproducts.com/nsp120.html
In any event when mixing such epoxies you MUST use the 'two-pot' method
for mixing to be SURE that the epoxy is precisely, correctly and ****
thoroughly ***** mixed.

For simple rust on intact steel, just grind, sand or blast, etc. to
bright metal, then roll-on the lining epoxy. For surface corroded
tanks you might want to consider first lining/strengthening with glass
cloth, tape, etc. then overlay with the lining epoxy.
;-)


In article , Robert
Larder wrote:

"Peter Hendra" skrev i en meddelelse
...
Hi,
A fellow boater here in Trinidad has rusty steel water tanks with a
snip
If so, what would be the most cost effective (cheapest) internal
coating?

Coal Tar Epoxy not a good idea.
A temporary fix might be a cement wash. Never tried it myself, but I believe
it was a commonly used treatment in "the old days".
HTH
Bob Larder