passivation

Short definition from Wiktionary

Noun

1. 1
   The process of making a material passive (non-reactive) in relation to another material prior to using the materials together.
2. 2
   The spontaneous formation of a hard non-reactive surface film (usually an oxide or nitride) that inhibits further corrosion.
3. 3
   Conversion of a non-passive dynamical system into a passive one.