Steel Fuel Tank Internal Coating Recommendations

Magnon

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Hi, a friend is rebuilding a Norton Commando, he tells me the inside of the fuel tank (Roadster) is rusted with flakey bits, has anyone got any experience good and bad of using proprietary coating kits?

Thanks in advance :okay
 
I asked about getting mine done and the guy doing the paint on the outside said that to do it properly he’d need to cut a hole in the bottom so I left the idea well alone.

Tell him to buy some phosphoric acid, tip it in the tank, add water to the top and leave it. He may need to do it a couple of times but it’ll do the job. The best way to get phosphoric acid is to buy it from a garden centre and you get it 80% strength rather than paying more for proprietary rust remover liquids which will be around 50% and cost a lot more when you work it out.
 
I used Andy Malton at Motorcycle Dent Repairs in Pickering for my Z1300 and GT750 tanks, as the amount of rust and shite inside them was beyond belief.....no amount of home potions worked.
He's not cheap but he's thoroughly professional, and can deal with any amount of internal corrosion or external dents without affecting the outside paint.
My GT750 tank turned out to be leaking like a sieve when leak tested, due to the amount of metal loss, so I okayed it for him to strip it and silver solder the leaks.
When stripped it was found to have been previously crash damaged and poorly repaired, but Andy did such a good silver soldering job and smooth down that it not only passed a pressure leak test, it also only needed basic priming in order to paint it.
Both tanks were zinc passivated inside after he'd removed all the rust and crap, so they were like new again.
I don't mind paying for a professional job like that, and if I'd bought any other tanks, they'd still be forty odd years old and in as dodgy a condition as mine were anyway.

However, although he doesn't like or normally advise to put any tank lining stuff in, due to his concern over the amount of metal loss from the GT750 tank, he recommended that I treat it with POR-15 tank sealer.
It's the only one known to be ethanol resistant, so I got some from Frost Automotive and put it in myself.
It's awesome stuff but very dangerous, so read and follow the instructions very carefully if you get some.
 
Many thanks for taking the time to reply gentlemen, I've emailed your experiences and suggestion over so he (Malc) can decide how he wants to proceed.

Once again thanks
 
https://www.frost.co.uk/por15-motorcycle-fuel-tank-repair-kit/

This includes the stuff mentioned by Tarka. He’s right, it’s good but nasty stuff. Rubber gloves plus good ventilation essential.


Plus one for this , but three points
1) Need to get rid of all the loose rust, I used water detergent and counted in 10 random sized nuts and bolts. Jiggle the tank around remember to invert the tank. The leak on mine was on the top, probably caused by condensation. Keep rinse repeat until the water runs clean.

2) For the metal ready and primer products I left the tank unmasked, since both a caustic and will dull or remove paint. I worked outside and kept hosing the outside of the tank. When it came to the final silver paint application I fully masked the tank as the paint is Very thin and if you spill it on the tank and dont see it , it will stick like shit to the preverbial.

3) lastly after the last caustic / aqueous treatments you have to flush the tank with clean water. This is when flash rust comes. So after the last water flush , I poured in about 150 mls of Methalayted spirits. Slosh it about, throw away , refill with another 150 ml and leave to stand for 10 mins to let the meths combine with any water held in the tank internal seams. Discard then put the tank in a warm place to dry. Windowsill, airing cupboard for at least 2 or 3 days before the sealer application.

Reason for this is most tank sealants use an iso cyanate PU system that cures on contact with moisture. Hence the air cures them. If there is any moisture in the tank, the coating will cure and skin up, as the carbon dioxide comes off in the cure a void will occur under the paint. Result misery, and the oft heard comments “ dont buy tank sealers they are rubbish, they fall off etc.
 


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