Passivointikäsittelyä

Passivointikäsittelyä, known in English as passivation treatment, is a surface finishing process primarily applied to metals, most commonly stainless steel, to enhance their corrosion resistance. The fundamental principle behind passivation is the formation of a thin, invisible, and highly protective oxide layer on the metal's surface. This layer acts as a barrier, preventing the underlying metal from reacting with corrosive substances in its environment.

The process typically involves cleaning the metal to remove any contaminants such as grease, oil, or embedded particles. Following cleaning, the metal is exposed to a passivating agent. For stainless steel, this agent is usually an acid solution, such as nitric acid or citric acid. The acid selectively removes free iron from the surface, allowing chromium to react with oxygen and form a chromium oxide layer. This oxide layer is much more stable and less reactive than the original metal surface.

Passivation is crucial in applications where metal components are exposed to corrosive environments, including the medical device industry, food processing, chemical processing, and aerospace. Properly passivated stainless steel is less prone to rust, pitting, and other forms of corrosion, thereby extending the lifespan and maintaining the integrity of the components. The effectiveness of the passivation treatment can be verified through various testing methods, such as the salt spray test or copper sulfate test, to ensure the desired level of corrosion resistance has been achieved.