ilmanpäällysteen

Ilmanpäällysteen is a Finnish term used in materials science and related fields to refer to the surface layer that forms on a material when it is exposed to air, i.e., an air-formed coating. The word is composed of ilman (air) and päällyste (coating or surface finish) with the genitive ending -en, signaling possession or relation. In practice, ilmanpäällysteen describes native or spontaneously formed films such as oxide or hydroxide layers that develop without deliberate surface treatment.

Common examples include the native oxide layers that form on metals like iron, aluminum, or copper when they contact air. The exact composition and thickness depend on the material, environment, and exposure time. On iron, for instance, an oxide/hydroxide film may develop gradually, while aluminum rapidly forms a protective aluminum oxide layer. Copper can develop a patina consisting of various copper oxides and carbonates. These air-formed layers can influence properties such as corrosion resistance, electrical conductivity, and surface roughness.

In engineering and surface preparation, the presence of an ilmanpäällyste affects adhesion and the performance of subsequent coatings. For many applications, the native layer is removed or modified through cleaning, degreasing, mechanical abrading, or chemical etching to ensure proper adhesion of primers and paints.

The term is mainly used in technical Finnish literature and discussions of surface science, metallurgy, and coatings. Related concepts include native oxide layers, passivation, and surface pretreatment.