I picked up a ridgid 450 tristand chain pipe vise for free. The guy said it sat outside the past 6 years. There is some original paint on it and the rest is just surface rust. The chain that holds the pipe is completly seized up. Any tips in how to fix this. Its not something I have to have cause we already have 1 at work but if we could have 2 it would make things easier. Its a couple hundred bucks to buy one new and its not that important. If I can get the chain free it would work perfect cause I already have a few extra cans of enamel paint to paint the base with and then she could be put into use. Any help is appreaciated.

I sprayed some wd40 on a few links and let it penatrate for two hours but it made no difference.

WD40 is too wimpy for that, kroil, or at least some type of penetrant / bolt breaking spray.
ATF may also help, possibly heating it, or just buy a replacement chain ;P
(The chain has been a standard size for decades)

Don't be afraid to wack it with a brass hammer a bit, the chain is hardened, you won't easily bend it (Don't wack the vise tho), chain lube will be a good idea later....

Or soak it in a pail of used oil for a few days, then have at it with the hammer.

I'll offer how I got past the same issue with several the last few months - chain/pipe vises and chain wrenches.

1) soak them in vinegar for a few days
2) power wash them very well
3) soak them in hydraulic fluid for a few days

I may have had a few spots to work out here and there, but for the most part it would free them up.

All good suggestions, It's not roller chain, there is probably little rust inside the joints. I'll be surprised you if you can't free it up and need to get a new chain.
Graeme

We didnt have vinigar or extra hydrulic fluid sitting around at the shop. We do however have half a drum of used oil so I put some in a bucket. Put the chain in the bucket earlier tonight and tommorow we will see what we come up with.

Does the clamping screw move easily?  If so, and you can't get the chain to loosen up, consider just driving out the pin that holds the chain to the screw.   Then take the chain to an industrial supply and match up a new piece of chain.

I have a Tri-stand that was thrown in on a garage sale purchase.  It is missing the handle so I'm using channellocks to tighten the screw.  I keep meaning to make a handle, but never get around to it.  I only use it now and then.

You might want to put some diesel fuel in with your oil to thin it out some.  Will help it penetrate easier.  It will take several days at least, to free that mess up.

Mike