A barrier coating is a partition between the core material and the environment surrounding the core. Coat properties such as solubility, porosity, and other factors can be designed for the intended coat function. Common barrier coating functions include:

carrier Coatings

A carrier coating is primarily used to overcome a mixing problem. Mixed dry components of varying particle size, shape, and/or density may de-mix upon routine handling. Also, uniformly mixing a small amount of one ingredient accurately and precisely with a larger amount of another material can be difficult. In either case, coating one component appropriately onto the other provides a uniform mixture of the dry components without the possibility de-mixing. 

surface modification

Particle surface modification is an inherent result of applying a coating. Nevertheless, some coatings are used specifically for surface modification. Material that "cakes" or "clumps" can be made to flow more freely with a proper surface coating. Dust control can be achieved in a similar manner. Color or texture can also be modified with coatings.

interface coatings

Imagine two or more solid particles or materials that need to be associated or attached to one another in some manner. An interface coating can be added to one or more of the materials to make the association. The interface coating can be "activated" under appropriate conditions of heat or "wetting" to achieve the desired association of particles. The Wurster process can be used to apply the interface and/or make the association.