Guys, adding an inert gas would be futile because it would almost certainly leak out.
The solution is not to attempt to keep the moisture out, it is to treat the surface chemically during manufacture so that it does not hydrate in service. There are a number of processes which achieve this.
Now that doesn't help much if the process used to make your blades was not hydration resistant. (I can't comment on RHC's specific processes because I don't know what they are.) The only option is to rigorously follow the ADs and service bulletins, in particular with regard to tap-testing and visual inspection. I personally place more weight on the visual inspection, and I would prefer to see another more reliable inspection method such as acoustics or thermography used rather than tap testing. I would treat ANY disbond with suspicion, even if it is within limits.
Regards
Blakmax