Fuel Tank Surface Rust

[rogerotto66s]

Local car guys suggested using 50/50 Muriatic Acid and water.
After using this the tank looked like new!

Today the inside of the tank is covered with brown surface rust.

What else do I need to do?

[InnoCooperExport]

I've not done it myself yet, but I am going to coat my tank with Fertan tank sealant. I've heard great things about it from others who have done it before.

[Polarsilver]

I have similar issues with an Audi URq .. re-clean the tank then add "In Line filter" before the pump & fill Tank with fuel .. whatever rust will still form above the full level .. so i accept & it becomes a longer term on going maintenance issue

[Fanfaniracing]

Look that the Tank is always full.

If you don't use the car you can add a bit of 2T Scooter oil.

[mk1]

My preference is de rust with Phosphoric acid & leave it to dry naturally, that doesn't rust for ages, but if you are using most other acids you can neutralise with caustic soda solution. This will stop the component rusting for a reasonable time.

Think about it though, if you are removing rust with an acid solution, this same solution, in most cases will also promote new rust formation once the item has been allowed to dry & stand for a while.

De rust, neutralise, dry & then paint or treat.

[surfblue63]

Take care if using a tank sealer. I brought a Mk3S that had almost had its restoration finished only to find that fuel would not pass between the tanks. It turned out that a sealant had been used inside the tanks. There was a small filter in the right hand tank were the balance pipe connected which was blacked with sealant. Luckily we were able to dislodge the filter enough to allow fuel to pass to the left side without having to remove the tank from the car.

Also rust in fuel tanks is not helped by these ethanol containing fuels. Even if you leave the tank full the hydroscopic nature of the ethanol will allow water to be retained and corrosion to start.

[woodypup59]

Also rust in fuel tanks is not helped by these ethanol containing fuels. Even if you leave the tank full the hydroscopic nature of the ethanol will allow water to be retained and corrosion to start.

Another "advantage" of ethanol.

[surfblue63]

There's no advantage to ethanol, it might reduce CO2 at the exhaust, but it increases fuel consumption, costs more in CO2 during manufacture, causes deforestation, takes land that could be used for food production. All in all it is a complete waste of time and will not help with climate change. Just another load of junk put out there by people and governments with a vested interest in the production of ethanol and taxation of the working man.

[Mini Mad Swede]

Weird this, thought the ethanol mixed easily with water and hereby draw it with the fuel in 'small amounts' so instead of leaving it (water) behind it shouldnt cause rust anymore.
Well, I stand corrected on this matter now.

As for cleaning/neutralising/drying a fueltank after that treating with 'derustment' surely its quite clear bare metal will rust again! Personally would pour some oil into it and 'slosh around' so it hopefully wont rust again before getting fitted and in use again.

[Tim]

Yes ethanol can be added to a fuel tank that contains a small amount of water. It absorbs the water and passes through the carby taking the water with it.

Tim

[Peter Laidler]

Has anyone thought of bead blasting the tank inside and out and dropping it into a phosphating tank. This grey protective coating will effectively prevent rust forming again, The MoD use it extensively and overpaint it with a chemical paint, made by HENKEL chemicals called SUNKORITE.

[Tex1965]

Just going though cleaning both tanks on my Mk2s. Using Citric acid, as I have plenty available.

After 3 days, drained the first one (RH) last night. Rust is gone. Flushed with warm water, drying with hot air. Put some light oil & wd40 shaken a bit to get oil everywhere.

There is a filter in RH tank too. This one has seen better days. Flows through, but I'm afraid it might get worse (bits missing already from the outer sheat/mesh). I didn't have the guts to remove it - maybe I should. How tight it is.. how to remove.. (only filler neck hole to operate from)?

2years ago I did one tank with Citric acid, not oiled just stored - no rust. Gave some WD40 now and left it for better days (mk1s).

I agree Phosforic Acid would be the best method, as Mark suggest. 1liter of 85% acid = 30€, good for 10Liters. So one would need 3Liters diluted to fill Mini tank. Right?

[swindrum]

... you can neutralise with caustic soda solution. This will stop the component rusting for a reasonable time.

De rust, neutralise, dry & then paint or treat.

Mark, what is the mix ratio you use for the caustic soda solution?

Thanks!
Sean

[mab01uk]

Is anyone still selling these plastic RH tanks from Australia?
No problem with rust or E10 petrol then!

Plastic RH Tank:-
"....IT TOOK 2 YEARS TO MAKE THE MACHINE TO MOULD THESE TANKS,,,THIS IS THE SAME MATERIAL USED TO ROTORMOULD MARINE FUEL TANKS, TESTS WERE DONE BY SOAKING STRIPES OF HDPE IN GLASS JARS, WITH ALL TYPES OF FUELS I COULD FIND , OVER THE LAST 2 YEARS , EVEN THINNERS , ACITONE & ETHANOL , WITH ///// NO EFFECT /////// ON THE MATERIAL AT ALL ...."
http://mk1-forum.net/viewtopic.php?p=144062#p144062

Plastic RH Tank:-
http://mk1-forum.net/viewtopic.php?f=5&t=9048&p=67284

[rogerotto66s]

Thanks to your feedback.
I have read many dozens of posts of this forum and others.
surprised that cleaning a fuel tank has so many different personal preferences (some rather strong).

So... I have opted to start over.

Starting with the LH tank I again have plugged all the holes (vent, outlet, fuel level gage).
I poured straight vinegar in through the fuel intake.
It has been sitting since TH afternoon.

My plan for Monday / Tuesday is :
- pour out vinegar
- rinse with baking soda and distilled water (several times) to neutralize the acid
- rinse with acetone to remove remaining water
- unplug holes
- dry with hair dryer and shop vac (blowing air in)
- coat inside with 2 stroke oil

If this method is not acceptable then I may explore using the phosphoric acid rinse.

I will provide an update in a few days.

Thanks to all.

[timmy201]

I haven’t seen any plastic tanks out here for years. The guy who was making them sold the production gear and the subsequent owner hasn’t made any yet

[Dr.Mabo]

I haven’t seen any plastic tanks out here for years. The guy who was making them sold the production gear and the subsequent owner hasn’t made any yet

I bought a new RH plastic tank years ago but never used it. If anybody is interested, I give it away for GBP 260 plus shipping. It is located in Germany.

so long
the Doc

[winabbey]

This is the nylon mesh filter inside the tank - part ARA1200.

Tank Filter.jpg

It's a friction fit over the exit tube so can be removed by pushing something through the tube from outside. You can then fit an external filter in the line to compensate.

[mk1]

No real "ratio" in the caustic soda neutralising rinse. Just a good strong mix. But be careful mixing it! Remember it's exothermic when you mix it up!!! can spit if you don't add the soda steadily.

I have never used anything as mild as baking soda, but I am sure it will help neutralise the acid.

Price quoted above is a bit steep! 5lt of 85% is about £60, I last got 4 x 5lt, at about £120. Made it up into 200 litre with water & have been using it consistently for about 3 years now. Still works a treat.

[rogerotto66s]

This is the nylon mesh filter inside the tank - part ARA1200.

Tank Filter.jpg

It's a friction fit over the exit tube so can be removed by pushing something through the tube from outside. You can then fit an external filter in the line to compensate.

I would like to replace my in-tank filter.
What are my options?