Paint for the inside of a fuel filler neck

Does anyone know the correct type of paint(if any) for painting inside a fuel filler neck?
got a spare filler neck in good condition, just a bit of surface rust on outside, I'm going to paint the outside again to protect it. There was a bit of surface rust inside a few inches from the top, probably where the petrol nozzle rubbed it.  I've sanded it back to bare metel, so need to paint the inside too,  anyone got any ideas of the correct paint to do it please?
Thanks.

Have a look at the e-coat procedure.  I did mine 3 years ago and painted the outside with a wurth underseal,  no issues since -  I do live in Sydney so tin worm is less of an issue. 
Gav

I used this stuff on the outside and inside (where I could reach) of my filler neck, I also painted the suspention, wishbones, the floor pan, the wheel arches etc with the same stuff.
http://www.rust.co.uk/epoxy-mastic-rust-proofing-paint/c28117/

I can't see why you can't use any old paint on the inside as it's not sitting in petrol, you may get a little splash from filling up but the most damage will happen when you put the petrol filler nosel in.

I would recommend the epoxy mastic for the out side, I also painted on top of the epoxy mastic in white hammerite (to match the car) and then a good coating of waxoil about 10 years ago, the Hammerite has mostly chipped off but the epoxy mastic is still hold on very well.

Hi,
Thanks for the replies.
   I will look into them both. Outside isn't an issue really, just going to put loads of primer, topcoat, lacquer and waxoyl on.
   It's only one bit on the inside that's the issue, otherwise I'd have binned it, problem is it's exactly where the nozzle has rubbed, so want to be careful so it's doesn't flake off again.
   I was thinking etch primer or zinc 182, then normal spray and petrol resistant lacquer on top.
   Do you reckon that would be ok?

Yes that should be fine for the inside.

Ok, thanks a lot for your help