chromatekäsittelyn

Chromatekäsittely, often translated as chromate conversion coating or chromating, is a chemical process used to provide corrosion resistance and improve paint adhesion on metal surfaces, particularly aluminum and its alloys. The process involves immersing the metal in a solution containing chromic acid or other hexavalent chromium compounds.

During the chromate treatment, a chemical reaction occurs on the surface of the metal, forming a thin, protective layer. This layer is typically a mixture of metal oxides and hydroxides, along with chromium compounds. The resulting coating is usually thin and transparent or slightly colored, ranging from pale yellow to iridescent brown, depending on the specific chemicals used and the alloy being treated.

Chromate conversion coatings are widely used in various industries, including aerospace, automotive, and electronics. They are applied to components like aircraft skins, automotive parts, and electronic housings. The primary benefits are enhanced protection against corrosion, especially in humid or saline environments, and an improved base for subsequent painting or powder coating. The coating can also reduce electrical contact resistance in certain applications.

While effective, hexavalent chromium is a hazardous substance. Environmental regulations and health concerns have led to the development of alternative, chromium-free conversion coatings. These alternatives aim to offer similar performance characteristics without the associated risks of hexavalent chromium. However, chromate conversion coatings remain prevalent due to their proven effectiveness and established application processes.