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A coating is a covering that is applied to the surface of an object, or substrate. [1] The purpose of applying the coating may be decorative, functional, or both. [ 2 ] Coatings may be applied as liquids , gases or solids e.g. powder coatings .
Polymeric coatings are another area of applied grafting techniques. In the formulation of water-borne paint, latex particles are often surface modified to control particle dispersion and thus coating characteristics such as viscosity , film formation, and environmental stability ( UV exposure and temperature variations).
Surface engineering techniques are being used in the automotive, aerospace, missile, power, electronic, biomedical, textile, petroleum, petrochemical, chemical, steel, cement, machine tools and construction industries including road surfacing. Surface engineering techniques can be used to develop a wide range of functional properties, including ...
The desired coating material is typically dissolved or suspended into a precursor solution or slurry (sometimes referred to as "ink") and delivered onto the surface of the substrate through a precise coating head known as a slot-die. The slot-die has a high aspect ratio outlet controlling the final delivery of the coating liquid onto the substrate.
In general, the lower the surface tension of a liquid coating, the easier it will be to form a satisfactory wet film from it. The difference between the surface tension of a coating and the surface energy of a solid substrate to which a coating is applied affects how the liquid coating flows out over the substrate.
Thermal spraying techniques are coating processes in which melted (or heated) materials are sprayed onto a surface. The "feedstock" (coating precursor) is heated by electrical (plasma or arc) or chemical means (combustion flame).
Various thin film characterization techniques can be used to measure the physical properties of PVD coatings, such as: Calo tester: coating thickness test; Nanoindentation: hardness test for thin-film coatings; Pin-on-disc tester: wear and friction coefficient test; Scratch tester: coating adhesion test
The act of applying a thin film to a surface is thin-film deposition – any technique for depositing a thin film of material onto a substrate or onto previously deposited layers. "Thin" is a relative term, but most deposition techniques control layer thickness within a few tens of nanometres.