Chrome plating in the USA is all electrolitic, not much het, there is some heat if baking is done after to prevent hydrogen embrittlement (good idea) but its basically 450° F.

From discussions with platers:

Frames are BAD, they trap fluid, and contaminate the next tank quickly.

Look at your frame, vent holes let brazing gas escape, but can trap acids and salts BAD.

Better the prep going in better coming out, read polish the raw metal first.

Copper plating is used often to get the polishing done faster, easier to polish copper than steel.

Then Nickel, then chrome for a durable chrome job.

Braze-ons snag buffing wheels, BAD Read frame flying across shop, then damage.

Bottom brackets are a problem, annodes can be set to encourage better coverage, say between the chainstays and bridge, but more work, more cost, polishing those areas are a hand tool zone, more cost.

Unless you get a guy who is desperate, its going to cost. In SoCal, $650 to $700 for a West Coast Chopper quality job.

If the frame has some plating now, more trouble, as it has to be "reversed" off, and THAT can ruin a frame if in too long, read undo the silver and or brass. The old chrome has to come off first, Columbus is a bit trickier as it is Chromemoly... chrome in the tubing steel can be removed!

All these hurtles can be overcome, just takes time and or money.

A chrome shop that mostly does bumpers is not the place to go, a plater that has done the drill prior is, but they will not be as cheap.