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Diesel Fuel Tank Corrosion Issue



 
 
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  #1  
Old September 4th 06, 11:05 AM posted to rec.autos.tech
Barath
external usenet poster
 
Posts: 5
Default Diesel Fuel Tank Corrosion Issue

Dear All,

I have following this grp a lot quite lately and found it
justifying to post my query here.. I am associated with a leading OEM
manufacturer of commercial vehicles in India. We are grappling with a
rather familiar problem right now - FUEL TANK CORROSION..

To have a forward on this problem. Mild steel uncoated tanks corroding
at the weld lines thereby causing leakage issues especially at the
bottom. Also the tank construction incorporates baffles which makes
reaching inside quite tough.

It is my thinking that the fuel tank corrosion happens especially when
the humidity inside the closed tank is high which causes water-vapor to
condense and react with steel, thus giving rise to excessive rusting.
The water vapor usually seeps into the fuel tanks along improper weld
lines, which serve the purpose of defective zones. Also the presence of
sulpher in diesel, especially in the presence of water at the bottom of
the tank, aggravates this situation causing the weld lines to
preferentially corrode in the absence of oxygen thereby causing the
leakage that we are experiencing. Also the rust particles as a result
clog the diesel fuel filter and the pump thereof.

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

Ads
  #2  
Old September 4th 06, 12:22 PM posted to rec.autos.tech
external usenet poster
 
Posts: n/a
Default Diesel Fuel Tank Corrosion Issue


"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.


  #3  
Old September 5th 06, 07:30 AM posted to rec.autos.tech
Barath
external usenet poster
 
Posts: 5
Default Diesel Fuel Tank Corrosion Issue

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. ??

Thanks again !!
wrote:
> "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.


  #4  
Old September 5th 06, 07:36 AM posted to rec.autos.tech
Barath
external usenet poster
 
Posts: 5
Default Diesel Fuel Tank Corrosion Issue

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. ??

Thanks again !!
wrote:
> "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.


  #5  
Old September 5th 06, 01:15 PM posted to rec.autos.tech
external usenet poster
 
Posts: n/a
Default Diesel Fuel Tank Corrosion Issue


"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.


  #6  
Old September 6th 06, 02:44 AM posted to rec.autos.tech
« Paul »[_1_]
external usenet poster
 
Posts: 123
Default Diesel Fuel Tank Corrosion Issue

Barath wrote:
>
> 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. ??


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:

Put the o back in hotmail.com for it to work.
He is in Calcutta now and will be returning to Houston October.
  #7  
Old September 6th 06, 01:31 PM posted to rec.autos.tech
Barath
external usenet poster
 
Posts: 5
Default Diesel Fuel Tank Corrosion Issue

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




«» wrote:
> Barath wrote:
> >
> > 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. ??

>
> 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:
>
> Put the o back in hotmail.com for it to work.
> He is in Calcutta now and will be returning to Houston October.


  #8  
Old September 6th 06, 01:39 PM posted to rec.autos.tech
Barath
external usenet poster
 
Posts: 5
Default Diesel Fuel Tank Corrosion Issue

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




«» wrote:
> Barath wrote:
> >
> > 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. ??

>
> 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:
>
> Put the o back in hotmail.com for it to work.
> He is in Calcutta now and will be returning to Houston October.


  #9  
Old September 6th 06, 06:47 PM posted to rec.autos.tech
external usenet poster
 
Posts: n/a
Default Diesel Fuel Tank Corrosion Issue


"Barath" > wrote in message
oups.com...
Thanks a lot guys for your inputs.Paul can you please elaboarate more
on Black Iron.
Never heard of it bfore...

*******
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.)




  #10  
Old September 7th 06, 12:37 AM posted to rec.autos.tech
« Paul »[_1_]
external usenet poster
 
Posts: 123
Default Diesel Fuel Tank Corrosion Issue

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

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.
 




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