coating

A coating is a material applied to the surface of a substrate to form a thin film that remains after application. Coatings are designed to protect, decorate, or impart functional properties such as corrosion resistance, wear resistance, electrical insulation, or optical effects. They are distinguished from bulk materials by their thin, surface-bound nature and are typically specified by dry film thickness.

Coatings can be organic, inorganic, ceramic, metallic, or composite. Organic coatings are often based on polymers (epoxy, polyurethane, acrylics); inorganic coatings include silicates and oxides; ceramic coatings provide high temperature and wear resistance; metallic coatings use nickel, zinc, or chromium for barrier or sacrificial protection. Coatings may be applied on metals, concrete, wood, plastics, and composites and are widely used in automotive, construction, marine, electronics, and aerospace industries.

Application methods include brush, roller, spray, and dip coating, as well as more advanced techniques such as electroplating, electrostatic deposition, chemical or physical vapor deposition, and sol-gel processes. Curing can be air-dry, thermally bake, UV or moisture cured, or multi-stage.

Key properties include adhesion to the substrate, film thickness (measured as dry film thickness), hardness, flexibility, toughness, and chemical or UV resistance. Performance is tested by adhesion tests, hardness tests, gloss, impact resistance, and corrosion or weathering tests.

Durability is influenced by substrate preparation, coating formulation, and environmental exposure. Common failure modes are delamination, blistering, chalking, cracking, and discoloration. Environmental and safety considerations address volatility, emissions (VOCs), and regulatory compliance.