Passivation ocurrs naturally in some materials, it’s why Stainless Steel doesn’t rust. A Passive layer is merely a thin coating of the oxide of the base material. This layer forms over time with contact with air. A passive layer can also be grown purposefully by immersion in oxidizing chemicals. Passivation as a process is mainly used for cleaning an descaling, Fotofab offers passivation per MIL-S-5002.