"Barath" > wrote in message
> POSSIBLE REMEDY :
>
> I was thinking of flushing the tank with phosphoric acid as a
> pre-treatment measure to Ferric Phosphates and then give a epoxy based
> primer coat in the inside as well as outside.
>
> Please adivice me on the same ...
>
> Regards,
> Barath

Moisture in the diesel fuel is the most probably cause, and it can be there
due
to contaminated diesel or by condensation. It is not too likely that it
enters via
porous weld zones (although lousy welds will be attacked far more rapidly
than
proper ones.)

If there is no moisture or other electrolyte in systems like this, corrosion
does not
occur. Sulfur content alone does not mandate corrosiveness, if there is no
effective
electrolyte to allow the electrochemical reaction to proceed.

Epoxy coating is one way to make the metal tanks resist corrosion, but the
polymer
has to be (1) one well suited for the application, (2) applied to a well
prepared metal
surface, (3) allowed to cure properly.

In production, you might find that it could be more cost effective to look
at different
materials of construction. Terneplate is a base metal (steel) which has
been dipped
in and coated by an alloy of ca 85% lead and 15% tin. It has been used for
years in
fuel tank construction.

Our company used to own a corporation which produced fuel tanks from high
density
polyethylene. I believe VW used them, and they were tough and non
corrosive.