What the best way to a petrol tank?

Rob H

Well Known and Active Forum User
VOC Member
The tank on my bike has a super paint job and is solid but unfortunately seems to be covered in surface rust on the inside.

in order to prevent this from making its way into the carbs/engine I would like to try and clean out the inside removing the rust.

Any members have any good tips or recommend any product to do this?

regs
Rob
 

timetraveller

Well Known and Active Forum User
VOC Member
Put a handfull of stainless steel nuts etc to the tank with some petrol. Put the filler cap back on and then spend a happy hour body building by shaking and rotating the tank. If you have gauze filters on the petrol taps then take the taps out first and blank off the tap bosses.
 

1660bob

Well Known and Active Forum User
VOC Member
I once had a T160 tank (well we all make mistakes...) It was like the hull of the Titanic inside-so much rust that you could shake it and hear the rust flakes rattling about inside- i ground the worst out with a nut and bolt soup as above but the results were not very good.Next stop I bought a gallon of stiff (50%) phosphoric acid from my local paint stripping depot and in it went- it dissolved away the threads on the crappy zinc/pot metal pattern taps and they fell out overnight, followed by the acid. That stain is still all over the garage floor. The tank however was cleaned back to the metal leaving a dull grey surface and I mean CLEAN-It leaves good steel alone.There was a tide mark on the sides of the tank where the acid had been and it was possible to shine a torch inside and see right into the seam weld folds and all that could be seen was the pock marks in the metal where rust had been. More acid, proper plugs in the tap holes and a made up seal of rubber sheet /large washer/nut and bolt to properly seal the filler orifice then rotate tank every half hour to clean all of the inside.At 50% strength the acid works that fast-2 hours -done.The only problem was there seems to be a reaction when you empty and swill out the tank (water)as the surface inside immediately begins to RUST -in minutes! so i had to re-do it several times until i managed to stop the re-rusting by emptying a can of WD40 into the tank and sloshing it about instead of water-this seemed to stop the flash rusting and i swilled it with petrol, perfect. As a tester I fitted clear plastic bodied, paper element fuel filters in the lines to see if anything nasty ever came out of the tank in use-in thousands of miles there was never a speck of rust/crud ever on them. I have heard people say phosphoric acid can cause hydrogen embrittlement of the steel ?? I don`t know about that but my tank always seemed fine.... Best of luck, Bob
 

AngloArm

Forum User
VOC Member
I was faced with exactly the same situation with my B.S.A. A 10 Petrol tank. A fantastic paint finish on the outside but loose surface rust inside.

There are several Petrol tank sealants on the market but you MUST confirm it will be resistant to the modern additives that are now used in petrol. I have read that there are some older sealant preparations that were not resistant and will cause terrible damage as they are dissolved by modern petrol additives and get into the carburettor and cylinder head. Do your research well for the latest and most up to date sealant product.

I chose to use a product called 'SLOSH' which I procured from 'Vintage Supplies' in Norfolk in October 2010. A half litre can of sealant should be more than enough for a Vincent tank.

After draining the fuel and inverting the tank to allow fumes to escape and evaporate, I removed the petrol taps and cut cork plugs to size to screw into the tap threads. I used the petrol cap to seal the fuel filler. Obviously follow the directions for your chosen sealant product, however I decided not to have my tank steam cleaned after draining the fuel. It's up to you but I don't have a steam cleaner and didn't like the idea in any case.

It was necessary to work outside and I waited for a warm and pleasant afternoon to do the job in the garden, kneeling down on a large piece of carpet underlay just in case I lost a grip on the tank. Just imagine the nightmare of dropping the tank on a hard garage floor!

I decided to use around 60 small flat washers, no larger than about the size of a penny. I considered using small nuts but thought they could cause damage if I was, shall we say 'over enthusiastic'. I emptied out the washers and rust particles every 5 or 10 minutes and rinsed the tank out with solvent then repeated the process around 6 or 7 times, until there was very little rust 'dust' coming out. I used cellulose thinners as suggested by the instructions with the product I chose. I was concerned about it's use, being a paint thinner. You must ensure it does not come into contact and damage your paint finish. I spent about 2 hours repeating the process. I then allowed the warm weather to dry the inside of the tank and finally inserted some old bed sheet into the tank and guided it as far as I could with a coat hanger to pick up anything remaining inside.

The next process involved introducing the sealant. Replacing the cork plugs and petrol cap, I gently turned the tank around and over for some time before emptying the tank contents into a large glass measuring jug, to work out how much had adhered to the inside of the tank. I repeated the process several times before finally draining the tank but continuing the turning action for another 5 to 10 minutes. There is still about 300 ml left over from the 500 ml can, which I will use to seal another tank I have to work on. Be careful to remove any splashes of the sealant from paintwork as it will start to set and become very difficult to remove, possibly also damaging the paint finish.

The drying out process takes some time. The instructions suggested 72 hours. Initially I left the tank in a warm dry place, upright for half an hour then upside down, tilted forwards then backwards over the next few hours so as to try to make sure there were no drips collecting in one place inside the tank, as the sealant started to set. A small amount of sealant continued to drain from the petrol tap lugs for about 6 hours. Some spilt onto an old piece of carpet and a few days later it was rock solid, so be careful where you allow the tank to dry. There was no urgency to refit the tank so I gave it a week for the sealant to fully harden.

Give yourself a long afternoon and don't try to rush the job. Patience pays dividends.
 

redwitch

New Forum User
Non-VOC Member
tank maintenance. answer

The tank on my bike has a super paint job and is solid but unfortunately seems to be covered in surface rust on the inside.

in order to prevent this from making its way into the carbs/engine I would like to try and clean out the inside removing the rust.

Any members have any good tips or recommend any product to do this?

Hi there are a fex methods to get your tank inside clean, but first check that the metal is not going to make holes; usually you see paint starting to act stange outside. well; the idea take the tank, fill it with abrasive products and shake untill rust goes . you first clean the tank with a detergent soap, and water to take out all gas and sticky things, after taking out the tap, and putting cork or other to shut holes, you choose either small bolts and screws, or small gravels or even a bicycle chain , that you put into the tank. Add phosphoric acid or choloridric adid, diluted 50% with water ( take care and put gloves on ) and start singing: " shaking all over!" change the liquid a couple of times untill it goes out clean. it can take a while, and you can invit friends for a couple of beers, and pass them the tank. dry, with a air blower, let completely dry out, check inside for small holes, carefully with a lamp; It is time that you know if your tank is still OK or needs replacement.
then, you can use a polyuréthane resin to coat and protect the inside. do it outside, because it stinks hard. check that the resin you use can stand ethanol mixed gas. ( not all do ) the brands are : Petseal, Restom, or G4. you mix, put in the tank, shake again slowly, and let dry a few days before filling the tank with gas again. That's it, your Veenie is ready to hit the road. Remember to put the acid bottle out of reach.

good work, good runs, Hervé. ( apologies for my english, I am only a frenchman )
 

clevtrev

Well Known and Active Forum User
VOC Member
I once had a T160 tank (well we all make mistakes...) It was like the hull of the Titanic inside-so much rust that you could shake it and hear the rust flakes rattling about inside- i ground the worst out with a nut and bolt soup as above but the results were not very good.Next stop I bought a gallon of stiff (50%) phosphoric acid from my local paint stripping depot and in it went- it dissolved away the threads on the crappy zinc/pot metal pattern taps and they fell out overnight, followed by the acid. That stain is still all over the garage floor. The tank however was cleaned back to the metal leaving a dull grey surface and I mean CLEAN-It leaves good steel alone.There was a tide mark on the sides of the tank where the acid had been and it was possible to shine a torch inside and see right into the seam weld folds and all that could be seen was the pock marks in the metal where rust had been. More acid, proper plugs in the tap holes and a made up seal of rubber sheet /large washer/nut and bolt to properly seal the filler orifice then rotate tank every half hour to clean all of the inside.At 50% strength the acid works that fast-2 hours -done.The only problem was there seems to be a reaction when you empty and swill out the tank (water)as the surface inside immediately begins to RUST -in minutes! so i had to re-do it several times until i managed to stop the re-rusting by emptying a can of WD40 into the tank and sloshing it about instead of water-this seemed to stop the flash rusting and i swilled it with petrol, perfect. As a tester I fitted clear plastic bodied, paper element fuel filters in the lines to see if anything nasty ever came out of the tank in use-in thousands of miles there was never a speck of rust/crud ever on them. I have heard people say phosphoric acid can cause hydrogen embrittlement of the steel ?? I don`t know about that but my tank always seemed fine.... Best of luck, Bob
Phosphate treatment is always followed immediately by a de-watering oil.
 

macvette

Well Known and Active Forum User
Non-VOC Member
I derusted the tank on my 1972 Honda CB 500 using electrolysis. No acids and only removes rust, no metal. You can look the method up on t'internet but briefly you make an anode I used a steel coat hanger but make sure you remove the varnish from the hanger. Get a suitably sized plastic cap which fits your filler neck. Put a hole in the centre of the top to take screwed steel rod and drill a couple of vent holes in the top of the cap ( an aerosol top did it for me). Fix a length of coat hanger to the rod using a couple of steel nuts and the rod the cap with another couple of nuts and washers. Fiddle around with this assembly so that you can get it deep into the tank WITHOUT ANY OF IT TOUCHING THE TANK The plastic cap insulates the rod and hanger from the tank. Remove your fuel taps and plug the holes. Fill the tank with a solution of washing soda one tablespoon to the gallon. Refit your assembly making sure no metal part of it touches the tanlk. Connect the POSITIVE of a battery charger to the assembly and the NEGATIVE to a suitably bare metal part of the tank (rear mounting bracket?). Put the battery charger on trickle charge. A charger with an ammeter is best so that you can see the current draw.
Rust will collect on the coat hanger leaving sound tank metal behind. This method will not remove sound metal. You will need to clean the coat hanger and you might have to replace it as it is a sacrificial anode. This is not a quick method but is very safe as far as the tank is concerned. Whatever you do make sure you connect up as described. If you reverse polarity you WILL dissolve your tank.

As the tank derusts,the solution will go brown and the anode will collect an amazing amount of crud and you may have to change the solution after a couple of days. When your tank is clean, flush it thoroughly, empty it and dry it straight away because it will flash rust if not dried immediately. Now you can line it or not depending on your preference.
 
Last edited:

Rob H

Well Known and Active Forum User
VOC Member
I derusted the tank on my 1972 Honda CB 500 using electrolysis. No acids and only removes rust, no metal. You can look the method up on t'internet but briefly you make an anode I used a steel coat hanger but make sure you remove the varnish from the hanger. Get a suitably sized plastic cap which fits your filler neck. Put a hole in the centre of the top to take screwed steel rod and drill a couple of vent holes in the top of the cap ( an aerosol top did it for me). Fix a length of coat hanger to the rod using a couple of steel nuts and the rod the cap with another couple of nuts and washers. Fiddle around with this assembly so that you can get it deep into the tank WITHOUT ANY OF IT TOUCHING THE TANK The plastic cap insulates the rod and hanger from the tank. Remove your fuel taps and plug the holes. Fill the tank with a solution of washing soda one tablespoon to the gallon. Refit your assembly making sure no metal part of it touches the tanlk. Connect the POSITIVE of a battery charger to the assembly and the NEGATIVE to a suitably bare metal part of the tank (rear mounting bracket?). Put the battery charger on trickle charge. A charger with an ammeter is best so that you can see the current draw.
Rust will collect on the coat hanger leaving sound tank metal behind. This method will not remove sound metal. You will need to clean the coat hanger and you might have to replace it as it is a sacrificial anode. This is not a quick method but is very safe as far as the tank is concerned. Whatever you do make sure you connect up as described. If you reverse polarity you WILL dissolve your tank.

As the tank derusts,the solution will go brown and the anode will collect an amazing amount of crud and you may have to change the solution after a couple of days. When your tank is clean, flush it thoroughly, empty it and dry it straight away because it will flash rust if not dried immediately. Now you can line it or not depending on your preference.


Now that seems an interesting approach,
thanks to all for the tips
 

alscomet

Well Known and Active Forum User
VOC Member
cleaning out petrol tank

http://www.altelco.net/~jacil/clay/motorcycle/KElecSetup.html Have a look at this setup I have used it several times now and it works every time just keep your tank paintwork clean by wrapping the tank in clingfilm first before you start.
You may need to change the electrolite several times and it will take quite a few days but when you have finished the tank is as clean as if its been shotblasted inside. I then finish it off by sealing it with Slosh from Draganfly Motorcycles its easy to use and drys quite quickly.
 

Rob H

Well Known and Active Forum User
VOC Member
http://www.altelco.net/~jacil/clay/motorcycle/KElecSetup.html Have a look at this setup I have used it several times now and it works every time just keep your tank paintwork clean by wrapping the tank in clingfilm first before you start.
You may need to change the electrolite several times and it will take quite a few days but when you have finished the tank is as clean as if its been shotblasted inside. I then finish it off by sealing it with Slosh from Draganfly Motorcycles its easy to use and drys quite quickly.

Will give this a go, whats the best place to get washing soda from?
 
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