Welcome Tankyanker.
This thread is from 2009, and resurrected in 2016, and again yesterday by you. Look at the previous posting dates when searching around. However, threads like this one come back regularly as the topic is always relevant.
Don't use boric acid on stainless steel HT as it will become corrosive above 1600°F.
For stainless steels you either wrap in a stainless foil packet or use a clay type shield like ATP, NuClayer, Brownell's, or other slurry type surface protectant that is rated for 2000°F.
Also, carbonization is the process of decomposition of organic matter into carbon.
Carburization is a process of adding carbon to the steel (usually the surface).
De-carburization is the process of carbon oxidizing and leaving the surface devoid of carbon.