Ralf;
I to had a problem with rust. I've tried everything under the sun. So I went to the next extreme and heated my pocket and straight carry knives with a hair dryer just to warm it up, DO NOT get it hotter then you can handle, the temperture will be to high and you'll destroy some or all of the temper in the springs. They're is small room for error, not much through. then I pour Tuff Glide all over it, into it, and through it.
And set it aside to drip for a day or so, and let it dry. Pick it up and wipe off any excess and your good to go. I've taken what knives I could , apart and after 2yrs. They're perfect inside and out, pure carbon steel, sweating and condensing in my pocket!
The heat opens the pores of the metal and the Tuff Glide, and I've had great luck with Dura Lube also,impregnates the surface and dries to form a shield from moisture and then rust from forming, and yes, I got the idea from the comercials on TV, of course, on a rough day of using alot, I always wipe down the blade and thumb button with a TS marine Cloth, just to make sure on those surfaces, incase the,"shield", does where off from rubbing. Ironhorse