Even when reducing value-added casting, the use of high-quality boron nitride (BN) coatings is crucial for aluminum plants.
The biggest reason for continuing to use high-quality coatings is to continue to protect your investment, that is, refractory materials, launder and trough, etc. In the long run, using a protective coating that does not adequately protect the refractory will cost more money.
The coating extends the life of the substrate, thereby providing a sacrificial and protective barrier. Choosing the right coating and using it wisely will extend the life of the substrate, and the better the coating, the more castings can usually be obtained between recoats.
The correct use of high-performance BN coatings is essential to maximize performance.
The first is to apply the coating too thick, causing it to peel off. BN coating is most effective when applied to a dry film thickness of 50-150 microns. Spraying is the best method to control the thickness of the film and is effective for both hot refractory materials and cold materials.
The second is the thixotropy or rheology of the coating. The viscosity of these coatings depends on the composition of the shear rate. Because they are shear-sensitive components, they are pseudoplastic in nature and their viscosity depends on several variables. It is always best to thoroughly mix all paints before use, and use wise dilution methods as a tool to maximize the customer’s application.
Before and after filtering, the BN coating is a good choice. Because it is chemically inert to molten aluminum and has a lower density than most other coatings, defects are unlikely to occur.
Boron nitride, or just BN, is considered the industry standard best practice globally.
As a best practice, hexagonal boron nitride (h-BN) thermal properties fit most aluminium process conditions and provide the best lubricity and non-wetting properties for refractory materials.