The processes of surface treatments, more formally surface engineering, tailor the surfaces of engineering materials to

• control friction and wear,
• improve corrosion resistance,
• change physical property, e.g., conductivity, resistivity, and reflection,
• alter dimension,
• vary appearance, e.g., color and roughness,
• reduce cost.

Ultimately, the functions and/or service lives of the materials can be improved.

Common surface treatments can be divided into two major categories: treatments that cover the surfaces and treatments that alter the surfaces.

Organic Coatings: The organic coatings apply paints, cements, laminates, fused powders, lubricants, or floor toppings on the surfaces of materials.

Inorganic Coatings: The inorganic coatings perform electroplatings, autocatalytic platings (electroless platings), conversion coatings, thermal sprayings, hot dippings, hardfacings, furnace fusings, or coat thin films, glass, ceramics on the surfaces of the materials.

Hardenings: Selective hardenings can be done by flame, induction, laser or electron beam.

High Energy Treatments: Common high energy treatments include ion implantation, laser glazing/fusion, and electron beam treatment.

Thin Diffusion Treatments: Thin diffusion processes include Ferritic-nitrocarb, boronizing, and other high temperature reaction processes, e.g., TiC, VC.

Heavy Diffusion Treatments: Heavy diffusion processes include carburizing, nitriding, and carbonitriding.

Special Treatments: Some special treatments, such as cryo, magnetic, and sonic treatments, affect not only the surfaces but also the bulk materials.