Diesel Fuel Tank Corrosion Issue

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.

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 see> >

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 see> >

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.

Metal tends to corrode/rust where it is most stressed, like sharp bends and seams. Be careful with heavy metals in diesel. The sulfur reacts with the metal. That is why diesel fuel systems are black iron. Put this into Google and follow up on the links: diesel fuel tank coating Email a friend of mine - he may be able to help: Mo snipped-for-privacy@htmail.com Put the o back in hotmail.com for it to work. He is in Calcutta now and will be returning to Houston October.

Thanks a lot guys for your inputs.Paul can you please elaboarate more on Black Iron. Never heard of it bfore...

and e-mailed your friend on this issue ..thnks for tht

regards, Barath

=AB=BB wrote:

Thanks a lot guys for your inputs.Paul can you please elaboarate more on Black Iron. Never heard of it bfore...

and e-mailed your friend on this issue ..thnks for tht

regards, Barath

=AB=BB wrote:

******* Black iron is about like cast iron. It is used in making pipe,etc, and is cheap. It is not overly hard (therefore is not likely to become embrittled like high strength steels in the presence of sulfur components or acids).

It has been used for years in sewer pipes, but has been supplanted by PVC, etc.

In service to the oil industry, thousands of tons of diesel are stored in tanks, onshore, to be transported offshore for use. I believe these tanks are stainless steel, since there is always a layer of water on the bottom. (Water is used to displace the diesel from the ships to the tanks)

There isnt normally MUCH water, but it is essentially always there, and has to be dealt with by centrifugation, filtration, etc so that it does not enter the engines.

We treat the water layer with a chemical to decrease microbial activity and corrosion. The microbes, principally Cladisporium resinae and others, cause severe problems in the fuel, especially when used in turbines.

The supply vessels, etc, often use the same sort of treatment in their fuel tanks. Having contaminated fuel, or corroded injection parts, is not fun when you offshore.

In short, if you cant afford anything but iron or steel tanks, then take the time to design the tanks so that stresses are minimized, welds are of high quality and normalized, and the shape factor of the tank is designed not to hold up water. (Water which passed through the system and is caught in an external separator/filter might even help.)

HLS pretty well answered it. It is plain old iron/steel pipe, fairly soft. Its dark grey in color, sometimes black. We use it on diesel fuel installations. Galvanized pipe is NOT to be used for diesel.