Removing rust from exhaust pipes

[Ian]

I have a few exhausts that need some work, including this one, which might be an unused RES pipe that came from Terry Silvester about 40 years ago.

In this case the pipe is by no means rotten, but the surface is rusty. The outside I can easily clean up, but what about the inside? Is there a reliable rust remover I could dip the whole thing in?

I have a few others to do too, and would prefer to save them rather than bin them.

[John Wakefield]

Inside should be OK as the residue of 2 stroke oil will have protected it. If you are continuing to store it pour some oil down it, old car oil will be ok, Plenty of rust removers out there Kurust etc, then paint with one of the heat resisting paints. Greeves used to sell DAG

[Ian]

This one is rusty inside as it was never used. I will see if I have some rust remover here.

[John Wakefield]

This one is rusty inside as it was never used. I will see if I have some rust remover here.

In that case just pour in oil and swill it around it will be fine for storage until you use it.

[IanCordes]

Immersing it in phosphoric acid solution will sort it out, Ian. You need a large enough plastic container with lid to house it. You can buy phosphoric acid by the gallon on ebay, and dilute it 10:1 when you immerse it. Leave it a couple of days, rinse & dry & job's a good'n. Phosphoric acid is no bother; it is an ingredient in Coca Cola... If you have ever wondered why soaking a tarnished old penny in coke overnight cleans it like a new pin....

[Jeff Morgan]

I've used white vinegar to take rust off the inside of steel fuel tanks, about £5 a gallon on line, go for the 8% acid strength, works well if you can fully immerse the work in it. takes a day or two. Or plug each end of the exhaust to clean off rust internally. I don't think it takes carbon/oil off though. Don't use it on your chips...……..

[John Wakefield]

Also an electrolysis method using a car battery charger an iron rod and washing soda as described by Dave MacGreggor in LL210, you will need a very large plastic container though.
Or you could sand blast the outside.
But it depends on whether you plan to then fit it to a bike, if you just want to conserve it in storage for use at some later date,then just give it a wire brush on outside to remove any lose rust and coat it with used engine oil and wrap it in newspaper, Pour about 1/2 litre of oil inside and seal off ends, swill it around to make sure oil gets all round then just store it. I have done this with other exhaust systems in the past,& it works fine but dont forget to drain out oil before you fit it to a bike, There will be a smoke trail on first use even so.