If a protective coating is to be applied - I would think you would want
to treat the metal with some chemical treatment to render the surface
rust resistant. this is not a paint of any sort - but something that
reacts with the metal itself. Navel Jelly(phosphoric acid) is one that
comes to mind. But it works best where rust is present by converting the
rust into something inert. Some of the POR products might be better.
After the treatment - then coat with some protective coating - not so
much to prevent rust - as to protect from physical damage from rocks, etc.

John

On 6/20/2013 1:53 PM, Dave Mcneely wrote:
> I guess I don't know the best answer to that.  However, when I put in a new tank, I used spray on undercoating on the entire exterior before mounting it.  I just thought it made sense.  Was I wrong?  To me, bare steel rusts, and coated steel is less likely to do so.  But what do I know?  mcneely
>
> ---- ralph meyermann <ralphmeyermann@GMAIL.COM> wrote:
>> Hi all me again! Ive got a question about my new fuel tank. My fuel tank is
>> bare steel would it be wise to coat the exterior with some form of paint/
>> bedliner stuff to prevent external rust or would that cause more rust?
>> Thanks again!!
>> Velma 82 na diesel westy
>
> --
> David McNeely
> .
>