"Passivation", in physical chemistry, refers to a material becoming "passive", being less affected by environmental factors (air, water). Passivation involves a thin outer-layer of insoluble metal oxide at the surface, so the underneath metal cannot react with the acid anymore.
Since centuries, to protect metals by rusting, mankind treats swords and knives blades making what is called "bluing": bluing is a passivation process in which steel is partially protect against rust, and is named after the blue-black appearance of the resulting protective layer. This thin layer is made by magnetite (Fe3O4).
You may bluing a knife blade, just using what you have at home.
First of all, clean carefully the blade from grease and fingerprints, using alcohol
Now, the blade is ready to be treated. To "passivate" the blade I use vinegar, but lemon or onion juice is effective as well
To accelerate and improve the chemical reaction, just warm the vinegar at the boiling point. Put the blade on the hot vinegar for 10 minuets or so
Final result: the knife blade is "blued", a thin magnetite layer will protect (partially) the metal from rust
Enjoy your bushcraft! :-)