found this on an engineering forum........
The proceedure is very much the same as removing rust but with different chemical. First, degrease completely and scrub thoroughly with detergent. Mix 1 cup of Muriatic acid with 3 gallons of water in a plastic bucket. NOTE; ALWAYS ADD ACID TO WATER. NEVER WATER TO ACID !!! (It WILL explode) Hang two or three copper wires (#12 or larger) around sides of bucket. Connect these to ground of battery charger. Hang item to be dechromed in fluid with positive lead connected. Be sure part doesn"t touch ground wires. Within a few seconds or minutes, depending on thickness of chrome, it should come clean. More or less time as required. When finnished, wash parts in mild soda water solution to nutralize acid. (Do this right way to prevent rust) As with any caustic acid, handle with care.
I would add that the fumes are 'unhealthy'
so should be done in a well ventilated area.
I should also add that by lowering the concentration of acid, the de-chroming would be slower and more controlable.
Kind Regards David