How do I remove nail rust stains from ceilings?

Is there some sort of chemical?

It is a concrete ceiling and has specks of rust all over it.

Do not just paint over it. The stain will bleed through the new paint and still be there.
You have to seal the stain with a sealer/primer, then paint.

My favorite is Bin 123. I have used Kilz, but it isn't as good a quality. Just my opinion.

I know baking soda removes rust.. I used on my junker of car before I got a new one.

if it is a concrete ceiling the rust stains are not from nails. there are 2 possibilities, stones containing iron and they absorb water from the atmosphere, the steel reinforcement is corroding.
tap the concrete with a hammer and listen for a hollow sound, if so call a spalling expert to repair, it is beyond the capability of a diy person.
if it is "ironstone", you would have to seal it with an epoxy sealer and then finish paint to your colour scheme.

Just paint over the area with Kilz

Whink is made for this purpose, you can find it at a hardware store, or walmart. Wipe it on, and watch the rust disappear.

rust aide or kilz paint - home depot

go to your local hardware store or simply paint over them.

vinegar will probably do the trick, just rub some one... maybe something like a tiny daub of bleach or alcohol. salt in water probably works too :] also, if the ceiling's it own color or has roughness to it, don't rub hard, just lightly daub it or something o-o;

If it's paint, just paint over it. Any plastic or metal material, use CLR. Sometimes citrus juice will work (lemon or lime). If that doesn't work, just go to a Home Depot and ask them.

If CLR doesn't work, paint the ceiling, you don't want it to look blotchy.

3 part water 1 part bleach or use Kilz primer!

Use CLR. It takes rust stains off of almost everything.

http://www.jelmar.com/CLRbasic.htm

remove any loose paint chips, Paint with a good Quality sealer/Primer. then repaint....

primer to cover the rust so that it will not bleed back thru.
paint to cover.

c.l.r.