pasywacj

Pasywacja, or passivation, is a chemical or electrochemical process that increases a metal’s resistance to corrosion by forming a thin, protective oxide or hydroxide film on the surface. The resulting passive layer is typically dense, adherent, and self-healing, reducing the diffusion of aggressive species such as chlorides into the metal.

The protective film forms spontaneously on certain alloys, notably stainless steels (where chromium oxide is key), aluminum (aluminum oxide), and titanium. The film acts as a barrier to corrosion and can regenerate after minor damage if the underlying metal remains intact. The effectiveness of passivation depends on surface cleanliness, alloy composition, and environmental factors.

Common methods include chemical passivation, which uses acids (such as nitric or citric acid) to remove free iron and promote oxide growth, and electrochemical passivation, which imposes a controlled potential to enhance film formation. Thermal passivation, conducted in oxidizing atmospheres, is another approach for some materials. Mechanical cleaning or pickling often precedes passivation to ensure a uniform film.

Applications are widespread in industries that require long-term corrosion resistance, including automotive, piping, architectural metals, and medical implants. Passivation improves reliability and reduces maintenance, but it does not modify bulk properties and cannot shield against wear or deep mechanical damage. The passive film can be damaged or dissolved by aggressive environments, necessitating re-passivation after cleaning, grinding, or surface finishing. Standards for passivation practices exist in various regions, guiding chemical composition, process parameters, and quality verification.