I have had seven pistols and a rifle hard chromed at Techplate in California (www.techplate.com). Prices are good and I usually have my gun back in about three weeks. If you email them with questions a gentleman named Marshall is good about responding.
Back in the late 1990s I read a Chuck Taylor article in HANDGUNS magazine. In it, he talked about a refinishing outfit by the name of Mahovsky's, and their proprietary Metalife SS Chromium M finish. Taylor said that he had several of his handguns done up with this finish, and then subjected them to such tests as submerging them in streams, snowbanks, etc..with zero damage or rust. I sent my blued Single Six to them and what I got back was a gun that was matte stainless in appearance. That was back around 1998 or so, and my gun still looks great. Their brochure states that their finish is guaranteed not to chip, crack, or peel; and so far I have no reason to doubt them. Give 'em a look-see at www.mahovskysmetalife.com. I don't think you'll be disappointed.
I just had a Ruger P90 Frame Coated by www.mahovskysmetalife.com and are real pleased with the outcome. They guarantee the finish for the life of the gun. If it lasts as well as it looks I will be real happy. All that I have read about their work has been good.
There are a few good choices listed here. I'd add www.Robarguns.com a firearms industry veteran that offers many features. Other good coating or chrome shops include www.APWcogan.com & you may want to look over www.Bearcoat.com .
Bob Cogan's AL based firm has many styles & options. They also have a lot of + feedback & do nickel/chrome firearm jobs.