Rust removal from a painted tank ?

[Grewth]

Here is my collection (so far) of 750F tanks.
CB750 in Flake Sunrise Orange with unfortunately a nasty dent in the top.
CB750F1 in rust all over, inside and out.
And CB750F2 in quite good condition except for a sodding great dent on the LH side.
All three are mucky on the inside,  fuel residue and maybe a failed liner on the F2, the F0 and F1 have loads of rust inside,  both fixed and loose flakes.
Fortunately none of them seem to have rotted out yet (I know where to look).
Ideally I'd like to use the Orange tank on my project bike, with it's 50 YO original paint.
I'm just wondering what the best way of dealing with the rust would be,  without damaging that paintwork any further  ? [ Guests cannot view attachments ] [ Guests cannot view attachments ] [ Guests cannot view attachments ]

[Athame57]

If the dent in the orange tank is free of any creases I think it could easliy be pulled out.
https://youtu.be/dity9_i6UVY

[Grewth]

If the dent in the orange tank is free of any creases I think it could easliy be pulled out.
https://youtu.be/dity9_i6UVY

There's a nasty crease just by the hinge point of the filler flap, unfortunately.
I've no doubt that some of the dent may pull out with DIY  paintless dent removal tactics, but not that crease which annoyingly runs across the panel line.
A professional could probably get it near perfect, but it's unfortunately not worth it for an old, faded, chipped paintwork

[Oddjob]

Not sure if I saw this on this site or the yank site but they use a process called electrolosis iirc. It’s essentially a large cork or plastic bung that seals inside the opening with a large bent nail sticking through it, they then fill the tank with water ( there may be something in the water, not sure) and then attach a battery charger to the protruding end of the nail and the tank. Evidently the electrical charge forces rust off the inside of the tank and makes it attach to the nail or bolt. After a few hours, remove the nail and clean off the rust and keep repeating until all the rust is removed. From all reports it’s an excellent way or doing it and dirt cheap. Rinse the tank in diesel afterwards to prevent flash rust.

Sure someone one here who has done this can expound on any parts I’ve got wrong. 

[Athame57]

Rinse the tank in diesel afterwards to prevent flash rust.

According to this youtube, and there are quite a few, you won't even need to that, unless perhaps if you are going to store it.  I gather that it does need to be done in a well ventilated place though, so not in your bedroom! 
https://youtu.be/OGjtx2BgK-U?si=hwR--QUGHkMm-VXx

[Grewth]

Thanks for that.
I'll have a good look tomorrow when I have some time to myself

[Laverda Dave]

DEOX-C, brilliant stuff. Pour it into the tank (it's powder), boil thf kettle and fill the tank to the brim. Wrap the tank up, leave it a couple of days (with some periodic shaking), undo the plug and be amazed at what comes out. I always dry mine with a hot air gun pushed into the filler cap. Once dry use diesel to stop it flash rusting.
You may have to do it a couple of times if the rust is bad.
DEOX-C is available direct from Bilt Hamber, about £18 with delivery.

[Oddjob]

Thanks for the links George. Watched a couple of vids of it being done, one used soda crystals and one used stuff used in outdoor swimming pools, being in the UK we don’t have a lot of outdoor swimming pools so soda crystals it is. £2 from Tesco’s btw.

I did think something was in the water so it’s nice to see that confirmed.

Everything seems fairly straightforward, seems simple. A spray can lid seems to be a good idea to suspend the anode in. Cut a slot to clear the cap hinge hole if required.

I like this method, you can just leave it to do it’s work and it gets too all the nooks and crannies, cheap as well. I’d say use hot water initially as it would dissolve the crystals better.

Got a nice tank with some light to medium interior rust, gonna give this a go myself soon.

[ozzybud]

I have a method I use that gives  great results.
I start with filling the entire tank with Evapo-Rust. It is available in Europe. Let it soak for a week. It won't harm paint or eat away at metal. Shake and drain thru a filter and save it for use again. Get 1/2 gallon of diesel and a pound or so of lightweight chain.shake the tank at all angles to scour the walls. Drain into a large pan. You will notice debris and remaining evaporust which is water based pool at the bottom. Pour the diesel back into the tank less the debris and water. Repeat until  walls are clean and diesel is coming out clean. The coating of diesel will prevent flash rusting until you fill it up.

[McCabe-Thiele (Ted)]

I used Evaporust on my 400 tank, in the UK it's become quite expensive, to fill the tank today would probably cost £60-70 on first filling.

[Oddjob]

I've bought Evaporust and TBH I didn't rate it much. Very expensive for what it is.

[DomP]

I've done the electrolysis or 'reverse plating' as I like to call it, really easy way to clean a tank up.

[Athame57]

I've done the electrolysis or 'reverse plating' as I like to call it, really easy way to clean a tank up.

How toxic can electrolysis make a small area's air if it actually does? I have a tank to derust myself but I don't want to aphixiate me and my dog    and I have no way of doing this anywhere else but my one room flat! 

[DomP]

I wouldn't like to say, I did it in my garage which is far from air tight