Chemical conversion coating is a surface treatment process that is used to improve the corrosion resistance of metal parts. The process involves the application of a chemical solution, which reacts with the metal surface to form a thin, protective coating. This coating is usually an oxide, phosphate or chromate conversion layer that protects the underlying metal from corrosion.
The chemical solution used in the conversion coating process typically contains a combination of inorganic acids, salts, and oxidizers. The solution is applied to the metal surface by dipping, spraying, or brushing.
The length of time the part is in contact with the solution and the solution temperature will vary depending on the specific process and the desired thickness of the coating.
The resulting coating is usually very thin, typically in the range of 0.00002 to 0.0005 inches (0.5 to 13 microns) thick. Despite its thinness, the coating provides a significant improvement in corrosion resistance by creating a barrier between the metal and the environment.
Advantages of Chemical Conversion Coating
Some of the advantages of chemical conversion coating include:
- Improving the adhesion of paints and other coatings to the metal surface.
- Providing a uniform coating that can cover complex or irregular shapes.
- Enhancing the appearance of the metal by creating a uniform finish.
- Being a relatively low-cost surface treatment method.
Some of the common metals that are treated with chemical conversion coatings include aluminum, magnesium, and zinc. These coatings are commonly used in industries such as aerospace, automotive, and electronics, where corrosion resistance is essential.