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A substance applied to
other materials to change the surface properties, such as color,
gloss, resistance to wear or chemical attack, or permeability, without
changing the bulk properties. Surface coatings include such materials
as paints, varnishes, enamels, oils, greases, waxes, concrete,
lacquers, powder coatings, metal coatings, and fire-retardant
formulations. In general, organic coatings are based on a vehicle,
usually a resin, which, after being spread out in a relatively thin
film, changes to a solid. This change, called drying, may be due
entirely to evaporation (solvent or water), or it may be caused by a
chemical reaction, such as oxidation or polymerization. Opaque
materials called pigments, dispersed in the vehicle, contribute color,
opacity, and increased durability and resistance. |
