A wide variety of stop-off technologies for heat treatment are used to selectively prevent the diffusion of carbon and/or nitrogen during atmosphere carburizing, carbonitriding, vacuum carburizing, and various forms of nitriding. In addition to selective stop-off, technologies are also available for scale prevention in open-fired furnaces. This article describes two stop-off technologies, mechanical masking and copper plating, along with stop-off paints/compounds. Prior to the application of stop-off paints, the part surface of the furnaces should be properly cleaned and dried. The article also describes the usage of stop-off paints in different heat treating processes, namely, carburizing and carbonitriding, deep carburizing, vacuum carburizing, nitriding and nitrocarburizing, and plasma nitriding. The article concludes by reviewing the application methods of stop-off paints: brushing, dipping, dispensing, spraying and stamping.

Thermal spray coating involves certain precoating operations, such as cleaning, surface preparation, and masking, that are critical to the overall quality of the coating system. In addition to these, certain other elements are considered prior to the coating, namely, customer requirements, coating function, part geometry, substrate metallurgy, structure, and thermal history. This article provides a detailed account of the various processes of surface preparation, namely, cleaning, roughening, dry abrasive grit blasting, and machining and macro roughening processes. It outlines the masking and fixturing techniques and stripping of coatings.

This article begins with a description of the advantages and disadvantages of thermal spraying. It provides a discussion on the importance of substrate processing prior to coating and the role of undercutting in repair. The article reviews the steps for substrate preparation, namely, cleaning, roughening, masking, and preheating. Information on the equipment and process variables of dry abrasive grit blasting are also provided. The article describes the roles of spray stream and the spray pattern for all thermal spray processes. It discusses the defects arising from poor temperature control and from the variables influencing the manipulation of the spray torch. The article concludes with helpful information on calculating the process efficiency of thermal spraying.

Immersion testing is the most frequently conducted test for evaluating corrosion of metals in aqueous solutions. This article focuses on the basic factors that are considered in different conditions of immersion testing. These factors are solution composition, temperature, aeration, volume, velocity, and waterline effects; specimen surface preparation; method of immersion of specimens; duration of test; and method of cleaning specimens. The article discusses the different conditions of immersion testing, namely, full immersion condition, high temperature condition, partial immersion and vapor phase condition, and alternate immersion condition. It concludes with a checklist of items that should be included in a standard report of immersion tests.

This article provides information on the factors influencing the selection of the proper corrosion-resistant coating system. It focuses on the proper execution of surface preparation and the available surface preparation methods. The preparation process includes the removal of visible contaminants, removal of invisible contaminants, and roughening of the surface. Solvent or chemical washing, steam cleaning, hand tool cleaning, power tool cleaning, water blasting, and abrasive blast cleaning, are some preparation methods discussed. The article describes the most common application techniques of coating as well as the equipment used. An overview of some of the most common coating inspection points and inspection equipment is also provided.

Selection of appropriate grades of steel will enable the steel to perform for very long times with minimal corrosion, but an inadequate grade can corrode and perforate more rapidly than a plain carbon steel will fail by uniform corrosion. This article describes the effect of chemical composition, heat treatment, welding, and surface condition on corrosion resistance of stainless steels. It discusses the various forms of corrosion and the important factors to be considered when selecting suitable stainless steel for application in specific corrosive environments.

This article provides an overview of plasma surface treatments for plastics. It covers the equipment and methods used in plasma processing, providing detailed explanations of the plasma discharge reactions and how they affect surface state and topography. It also provides information on contamination removal, plasma surface modification, plasma-induced grafting, and plasma film deposition.

This article discusses the principal process steps, specifications, defects, applications, advantages, and disadvantages of chemical milling (CM) in aerospace industries. The process steps include precleaning, masking, scribing, etching, final cleaning, stripping, and mechanical finishing. The article describes the variables that affect undercut and surface finish obtained by CM. The mechanical properties of chemically milled parts are also discussed.