"Barath" > wrote in message
ups.com...
> Thanks a lot for your immediate respose.
>
> Yes we considered the use of terne coated steels initially but due to
> environmental standards in place had to drop them. With regards to HDPE
> tanks esp via rotomolding .. The process by itself dosent allow
> reasonable costs associated with them esp in high production volume. So
> is the reason behind coatings that would inhibit this corrosion
> process.
>
> Also we are seeing this active corrosion in rectangular fuel tanks
> while our cylindrical counterparts dosent seem to experience any
> service failure. Is it because of the reduced contact area of the
> water. ??

I suspect that you are seeing the effect of water accumulation in the 90
degree
bends or weld zones. Surface tension effects tend to promote this.

No matter how these bends or welds are made, the metal is stressed in these
areas, and is more subject to corrosion than would be true with a gently
curved
(intrinsically less stressed) surface. You can sometimes 'normalize' or
de-stress
these zones, but I dont think this is your answer.

Even reducing stress and improving surface condition only is a temporary
improvement, usually. It is a matter of time and rate of corrosion until
you get
failures. .If you have bare steel exposed to water, you will get corrosion
unless you constantly treat the diesel fuel with chemical additives to
prevent it.
And that is perhaps not the best of solutions for you.

You WILL get water into the tanks over time, due to condensation, contam-
ination, etc.

This corrosive attack is a phenomenon which cannot be easily solved by
installing anodes in the tank since a complete circuit is required for
cathodic
protection to work. Galvanizing achieves this since all points are coated,
but
galvanizing will itself corrode and may generate zinc oxide solids into the
diesel.

If you try to coat the inside of the tank with an epoxy that doesnt stick to
the
surface well, or that releases over time, you are going to have some angry
customers.