A chemical conversion coating is a surface treatment applied to metals in which the metal undergoes a chemical reaction at the surface. This chemical reaction transforms the metal surface into a thin protective layer.
When applied to aluminum, a chemical conversion coating is sometimes called an aluminum conversion coating.
Chemical conversion coatings provide increased corrosion resistance and a uniform, inert surface for powder coating or paint adhesion.
Chemical conversion coatings are typically applied via immersion in a chemical tank or bath, or by brushing or spraying.
Types of chemical conversion coatings vary according to the metal substrate:
- Iron phosphate coatings – Used with steel
- Zinc phosphate coatings – Used with galvanized steel
- Chromate conversion coatings – Used with aluminum alloys