What's the best way to chemically remove scale from Copper after annealing with a torch? I'm dealing with small parts. Would Sulfuric Acid do the trick?

I Doubt it, as I use various acids to age (oxidize) copper.

Not chemically but if you take the scrotchbrite to it directly out of the quench it will all come off. You have to keep it wet or it seems to adhere. second idea again not chemically but bead blasting gives a nice finish.
I know that didn't answer the question but after dealing with it myself this is the best I have to offer.

Sparex #2 is what I have always used. Inexpensive, goes a long way, effective, not very dangerous... just what you want. Pretty standard stuff for the purpose. For faster action heat the parts or warm the solution. Use copper tongs to remove the work as iron will drive the copper out of solution and flash plate the parts.

You could also look at using a tumbler to polish them up. To brighten parts off of the zone annealer at work we have used Tarn-X.

In the pool supply section there is some PH Minus that you can mix with water and it does good on copper or steel. I think it is sodium bisulfate, someone else may know for sure. I have also seen Brian heat it up with a hot piece of steel first and it works quicker. I would treat it like acid though, take the same precautions.

Found this on wikipedia
Sodium bisulfate is used primarily to lower pH. For technical grade applications it is used in metal finishing, cleaning products, and to lower the pH of water for effective chlorination, including swimming pools. Sodium bisulfate is also AAFCO approved as a general use feed additive, including companion animal food

Thanks everyone. I just looked into it and Sodium Bisulfate = PH Down = Sparex #2.

I bought some PH Down a while back to clean rust off of some tongs (worked great). That was actually one of the first things I tried. It didn't seem to work, but I may not have used enough or may not have let it sit long enough. I also didn't heat it.

I still need to build a tumbler - it's on my to-do list. Funny how that list never seems to get shorter...

I'll try the PH Down again.

For small parts try clear vinegar, leave part in to clear of scale, warming the liquid can speed the process, rinse off with clean water after removal from pickling container

I use vinegar with a dash of salt, wire wool brings it up pink and new looking. For some reason the salt makes it work much better.

Most folks doing jewelry work have snagged an old crock pot to keep their pickling solution in. Ceramic container with a temperature controlled heat source---works a treat but please label it NOT FOR FOOD USE, so someone doesn't try to re-convert it into a crock pot later!

Ever been horrified to see someone using a lead melting pot as a little cast iron pot for food stuffs? They were not happy after my explanation. Neither was anyone else at the potluck...

Don't put Ferous metal in a Sodium Bi-sulfate solution that you plan to use for brass, bronze or copper. Use copper or brass tongs to remove piece from the solution.
Iron will "spoil" the solution for all non ferous metals. What it will do is plate copper and iron oxides on the surface of the non ferous metal. All your yellow or white metal will come out looking like copper.

So if you use Ferous metals in the solution, will that plate a solder joint and help the color match to hide the solder?

All of the solder joints I have tried it will. I don't remember if it plates nickel. I am talking about a very light coating that is easily abraded. I knew some stained glass workers who mixed some iron oxide in with the copper sulfate solution they used to "color" their solder joints.

also if you want to blacken the seem and entire peice gun blue hides solder seems. also on silver you can hide it by depletion gilding.