Passiivikalvo

Passiivikalvo refers to a thin layer of material that forms on the surface of a metal or alloy through a natural or induced chemical process. This layer is typically inert and serves to protect the underlying material from further corrosion or degradation. The formation of a passive film is a critical mechanism in the corrosion resistance of many metals, most notably stainless steels. In stainless steel, the passive film is primarily composed of chromium oxides, which form a dense, non-porous barrier. This oxide layer prevents aggressive species, such as oxygen and chloride ions, from reaching the metal surface and initiating corrosion.

The passive state is achieved when the metal is exposed to an oxidizing environment. If this environment is compromised, for instance by aggressive ions or a reduction in oxygen availability, the passive film can break down, leading to localized corrosion. The stability and integrity of the passive film are influenced by factors such as the composition of the metal alloy, the nature of the corrosive environment (pH, presence of specific ions), and temperature. Understanding and controlling the formation and properties of passive films is crucial in material selection and design for applications where corrosion resistance is paramount. Electochemical techniques are often used to study the formation, breakdown, and repair of these protective layers.