Coatings

Coatings are material layers applied to surfaces to protect, decorate, or impart functional properties such as hardness, corrosion resistance, thermal insulation, or electrical insulation. They can be formulated as organic coatings (paints, varnishes, lacquers, epoxy and polyurethane systems), inorganic coatings (ceramics, silicates), metallic coatings (zinc, chromium, nickel plating), or polymeric and composite coatings, often engineered as hybrids to balance multiple requirements.

Coatings are used across many sectors, including construction, automotive, aerospace, electronics, and consumer goods. Protective coatings prevent rust and wear on metal structures, provide weather and chemical resistance for concrete and wood, and serve as dielectric or thermal barriers in devices. Decorative coatings offer color, gloss, and texture while maintaining surface durability. The choice of coating depends on substrate compatibility, environmental exposure, required thickness, and service conditions.

Application methods span brushing, rolling, spraying, and dip-coating, as well as specialized processes such as electrocoating (e-coat), electroplating, thermal spraying, and vapor deposition techniques (chemical vapor deposition and physical vapor deposition), along with sol-gel and other surface-initiated processes. Film formation typically involves drying or curing, achieving adhesion through surface preparation, primers, and bonding promoters. Key performance criteria include adhesion, hardness, flexibility, impact resistance, gloss and color retention, and resistance to chemicals, UV light, and temperature.

Standards and testing frameworks from organizations such as ISO and ASTM guide quality control, including adhesion tests, hardness and bend tests, and corrosion or wear evaluations. Environmental considerations emphasize reducing volatile organic compounds, with waterborne and powder coatings increasingly favored, subject to regulatory compliance and lifecycle considerations, including recoating and removability.