coatning

Coatning, often spelled coating, is the process of applying a layer of material to the surface of an object to alter its properties or appearance. The layer remains adherent and serves a protective, functional, or decorative purpose. Coatings can be applied to metals, wood, plastics, textiles, and composites, among other substrates.

Coatings are broadly categorized as decorative and functional. Functional coatings provide protection such as corrosion resistance, wear resistance, thermal insulation, or electrical insulation, and may confer properties like hydrophobicity or biocompatibility. Decorative coatings are intended to improve aesthetics and may add color, gloss, or texture. Common coating materials include epoxy, polyurethane, acrylic and alkyd resins, ceramic or glass-like coatings, and metal platings such as zinc, chromium, and nickel, along with specialized polymers and composites.

Application methods vary with material and purpose. Liquid coatings can be applied by brushing, rolling, or spraying; powder coatings are applied electrostatically and cured thermally; metal plating uses electroplating or electroless processes; thin films may be deposited by chemical vapor deposition or physical vapor deposition. Surface preparation is critical and typically includes cleaning, degreasing, rust removal, and abrading to improve adhesion. Primers or underlayers may be used, followed by curing or drying under controlled conditions.

Quality control includes measuring coating thickness, adhesion, abrasion resistance, hardness, and environmental durability. Tests follow standards from organizations such as ISO, ASTM, or IEC. Environmental and safety considerations cover solvent use, VOC emissions, waste handling, energy consumption for curing, and end-of-life removal or recycling of coatings and coated substrates.