Konversiopäällysteitä

Konversiopäällysteitä, often translated as conversion coatings or passivation treatments, are chemical treatments applied to metal surfaces to improve their corrosion resistance and paint adhesion. These coatings work by converting the surface of the metal into a non-reactive layer, typically an inorganic compound.

The most common types of conversion coatings are chromate conversion coatings, phosphate conversion coatings, and newer, more environmentally friendly alternatives like zirconium-based or titanium-based coatings. Chromate coatings, historically widely used on aluminum and zinc, are known for their excellent corrosion protection and ability to act as a primer for paint. However, due to environmental and health concerns associated with hexavalent chromium, their use is increasingly restricted.

Phosphate conversion coatings, such as zinc phosphate and iron phosphate, are applied to steel, aluminum, and zinc. They provide a crystalline layer that enhances corrosion resistance and provides a good base for subsequent painting or powder coating. These coatings are often used in automotive and appliance industries.

More modern conversion coatings aim to reduce or eliminate hazardous materials like chromium. These technologies, often referred to as "thin-film" or "nano" coatings, utilize compounds of zirconium, titanium, or other elements to create a very thin, amorphous, and highly adherent layer. They offer good corrosion resistance and paint adhesion while being more environmentally friendly.

The application process for conversion coatings typically involves cleaning the metal surface, followed by immersion in or spraying with a chemical solution containing the desired coating elements. The metal surface then reacts with the solution, forming the conversion layer. Finally, the treated metal is rinsed and dried. These coatings are crucial in many industrial applications to extend the lifespan and improve the aesthetic qualities of metal products.