Phosphate coatings have a wide field of applications in the manufacturing industry. These coatings consist of layers of crystalline, water insoluble metal phosphates varying in crystal size depending on the:
- type of metal phosphate being used,
- metal substrate to be coated,
- characteristics of the metal surface.
The major applications for phosphate treatments fall into the following four areas:
- Pre-treatment prior to organic coatings
The pre-treatment of surfaces to be painted, E-coated or powder coated in order to provide improved coating adhesion and reduce the development of lateral corrosion under organic coatings.
The type of phosphate employed is usually determined by the degree of corrosion resistance specified. For maximum protection the coatings are normally sealed, passivated or coated in an oil or grease.
- Anti-wear coatings
Phosphate coatings can be used as efficient lubricant carriers to provide wear resistance to sliding surfaces.
- Phosphating as a production aid
Phosphate coatings can act either on their own or by carrying a suitable lubricant as a production aid in cold metal working operations such as cold forming and wire drawing. In these instances, the phosphate coating is applied to the raw metal rather than the finished article.