Picreator's Metal De-corroder is specifically designed to remove the rust but, it is rather expensive.
Here is the link to Pireator's website where you can find more information on their products.
http://www.picreator.co.uk/articles/1_about_us.htm
As with regards to cleaning and etching the blade, is always better safe than sorry.
PS: I don't really believe that is relevant whether the hilt is Jadeite, Nephrite (these two are known under the generic name of Jade), Serpentine or Onyx as they are very similar and sometimes it is very difficult even for connoisseurs to distinguish them. Yet, for your hilt my bet would be Onyx (it is a Turkish knife and they have some beautiful green Onyx deposits in Central Anatolia).
Just be aware that much of what is called "Jade" is not Jade (namely Jadeite or Nephrite) but Serpentine, Onyx and other similar minerals and sometimes even glass (most of the Chinese "jade" figures you can buy on the net are actually glass).