A coating is a covering that is applied to the surface of an object, the substrate.  Coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance.  In other cases, in particular in printing processes and semiconductor device fabrication (where the substrate is a wafer), the coating forms an essential part of the finished product.  Coating and printing processes involve the application of a thin film of functional material to a substrate, such as paper, fabric, film, foil or sheet stock.  Coatings may be applied as liquids, gases or solids.  (Wikipedia, Coatings, 1/7/2011)

Biocidal Coatings
Coating
Materials

Superhydrophobic Coatings

PTFE Coatings