You could call S&W Customer Service ( 1-800-331-0852) for an opinion. My guess is, they could be successfully coated, but I'm not sure why you would want to. These metal alloys are not susceptible to oxidation under normal circumstances.
APC Cogan says they can Cerakote it. I'll still call Cylinder & Slide. I'll probably call S&W also because now I'm curious what they actually use on the 329PD.
Another advantage to having that gun Cerakoted, it would probably make cleaning the cylinder easier.
I sold mine when I realized it was not possible to clean the outside of it after firing about a box of ammo.
Just got off the phone with Cylinder & Slide. They said Cerakote is ideal for Scandium and Titanium as they can't be blued. However, they did say you can still traditional electrolysis nickel or NP3. But those cannot be colored so if you want a color then Cerakote is the way to go.