The risk is if there are any areas near rusted through, the electrolytic acid bath will finish what the products of combustion or condensation started, so it is possible to have mufflers with holes after being submerged in the electrolytic bath.
If previously chromed, a part will need to be submerged in the electrolytic bath to remove the old chrome, this is where any potential defects will become apparent.
It IS a gamble to send in what looks like a solid muffler, only to have holes become visible after the old chrome is removed, because obviously, the electrolytic acid bath removes rust as well.
I have used a plater/metal worker for the past 10 years, when unseen defects have appeared, he is able to make the repairs in his shop. I have not had him plate any CB750 mufflers. He not only can weld, he also can lead in dents, so any defect he has been able to repair for me. The only problem with these old exhaust, IF a defect does exist, will require a patch and of course this likely would be visible after repair, considering the repair would have to be made from the outside. And, likely the patch will require a radius and the size of the patch could be considerable, so i am not sure if "my" plater would be willing or able to tackle a job of this sort. Small holes or dents, he can deal with, but larger holes, you wuld have to talk to him.
Based on my experience, I would suspect, the cost of chroming a set of exhaust would be in at least the $150 - $200 range, per pipe. Almost not worth it, unless you know your mufflers have good solid steel throughout.
"My" plater has chromed 2-cycle exhaust for me, he plugs the inlet and outlet. He is a motorcyclist, so the parts i send him are not just some chunk of iron to him.
If you want his contact information, let me know.
A couple guys in the club have used him and been VERY happy with his work. His plating quality is some of the best out there. But, i will say, he is a bit slow, turn around time may take 4-6 months.....