Surface treatments are used in a variety of ways to improve the material properties of a component. This article reviews information on surface treatments that improve service performance so that the design engineer may consider surface-engineered components as an alternative to more costly materials. It describes solidification surface treatments, such as hot dip coatings, weld overlays, and thermal spray coatings. The article discusses deposition surface treatments such as electro- chemical plating, chemical vapor deposition, and physical vapor deposition processes. Several types of coatings involve a heat treatment either after processing or as part of the coating process. The article describes surface hardening and diffusion coatings, such as carburizing, nitriding, and carbonitriding. It also tabulates typical characteristics of carburizing, nitriding, and carbonitriding diffusion treatments.