Although aluminum alloys are inherently corrosion resistant, there are many operating environments where they require additional protection. This article describes the conditions under which aluminum is prone to corrode and explains how to prevent it through the addition of conversion coatings and paints. It addresses some of the more common corrosion mechanisms, including corrosion driven by pH extremes, pitting corrosion, crevice corrosion, galvanic corrosion, and filiform corrosion. The article also describes in-plant as well as field application procedures for cleaning and coating, and discusses the advantages and limitations of the various materials and chemicals used.

The necessary precursor to a proper and durable finish is the preparation of the active aluminum surface to receive the desired protective finish that will allow it to have a long and attractive service life. This article helps those who work with aluminum in the many varieties of applications of such products. It describes the two main categories of cleaning that can be used with most any metal, namely, mechanical cleaning and chemical cleaning. The article provides a discussion on the laboratory evaluation of cleaners, field testing of cleaners, and cleaner types and procedures. It also describes the special cleaning procedures for aluminum alloys, such as steam cleaning and rotary wire-brush cleaning. The article reviews the use of temporary coatings and the use of maintenance coatings on aluminum. It provides information on the handling and storage procedures of aluminum alloys and the cleaning of specific applications of aluminum.

Mechanical finishes usually can be applied to aluminum using the same equipment used for other metals. This article describes the two types of grinding used in mechanical finishing: abrasive belt grinding and abrasive wheel grinding. It reviews the binders and fluid carriers used in buffing, and discusses satin finishing and barrel finishing. It also describes lapping and honing techniques that are of special interest in treating aluminum parts that have received hard anodic coatings. Honing recommendations for aluminum alloys are presented in a table.

Liquid penetrant inspection is a nondestructive method of revealing discontinuities that are open to the surfaces of solid and essentially nonporous materials. This article provides information on physical principles, evolution, description, and processing parameters of liquid penetrant inspection as well as materials used. It discusses some of the more generally used types of equipment used in penetrant inspection and their requirements. The article describes various penetrant methods and their selection criteria and provides information on precleaning and postcleaning of workpieces before and after penetrant inspection. The quality assurance and maintenance of penetrant inspection materials are also discussed. The article concludes with information on specifications and standards applicable to penetrant inspection.

Coating of cast irons is done to improve appearance and resistance to degradation due to corrosion, erosion, and wear. This article describes inorganic coating methods commonly applied to cast irons. The coating methods include plating, hot dip coating, conversion coating, diffusion coating, cladding, porcelain enameling, and thermal spray. Organic coatings have a wide variety of properties, but their primary use is for corrosion resistance combined with a pleasing colored appearance. The article discusses the various types of organic coatings applied to cast irons. Practically any degree of smoothness or roughness and requirement for color and gloss can be filled by organic coatings. The article describes abrasive blast cleaning, abrasive waterjet cleaning and finishing, vibratory finishing, barrel finishing, and shot peening for processing iron castings.

This article reviews the steps involved in presurface-preparation inspection: substrate replacement; removal of weld spatter, rounding of sharp edges, and grinding of slivers/laminations; and removal of rust scale, grease, oil, and chemical (soluble salt) contamination. It focuses on surface preparation methods that range from simple solvent cleaning to hand and power tool cleaning, dry and wet abrasive blast cleaning, centrifugal wheel blast cleaning, chemical stripping, and waterjetting for the application of the coating system. In addition, the article provides a description of the Society for Protective Coatings' (SSPC) standards and NACE International standards as well as the International Organization for Standardization (ISO) standards and International Concrete Repair Institute (ICRI) guidelines for surface cleanliness.

This article provides a detailed discussion on the functions, applications, types, and selection criteria of exterior and interior rail coatings. It includes a discussion on the corrosivity, inspection/maintenance, and qualification of applicators/inspectors/facilities.

This article focuses on the process design set-up procedure for brazing and soldering. It provides a detailed account of the types of base metals that can be joined by these processes, and reviews the factors to be considered to enhance the joint design. Criteria for selection of the right induction heating equipment to carry out the brazing or soldering operation are also provided. The article describes the types of brazing filler metals and joint designs. It also presents the types of inspection methods, namely, mechanical and visual, used to determine the quality of the brazed joint. Important considerations for the automation of induction-heated brazing applications are also discussed. The article concludes by emphasizing the need for documenting an in-control process which is a vitally important reference for questions or problems arising in the machine settings or part quality.

Metallographic examination is a critical step in the assessment of thermal spray coating characteristics. This article discusses the major steps involved in metallographic examination: sectioning, mounting, grinding, polishing, optical microscopy, and image analysis. It provides a discussion on etching to reveal grain structure. The article also provides recommendations for metallographic examination of some standard coatings.

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.

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.

This article provides an overview of surface contaminants that may affect the heat treatment processes and end-product quality. It presents information on the chemicals used to clean different surface contaminants of steels. The article discusses three types of cleaning methods, namely, mechanical, chemical, and electrochemical and their effectiveness and applicability. The mechanical cleaning methods include grinding, brushing, steam or flame jet cleaning, abrasive blasting, and tumbling. Solvent cleaning, emulsion cleaning, alkaline cleaning, acid cleaning, pickling, and descaling are chemical cleaning methods. The electrochemical cleaning methods include electropolishing, electrolytic alkaline cleaning, and electrolytic pickling. The article provides information on cleanliness measurement methods such as qualitative tests and quantitative tests to ensure product quality. Health hazards that may be associated with each cleaning method and the general control measures to be used for each hazard are tabulated.

This article provides information on personal protective equipment (PPE), consistent with the Occupational Safety and Health Administration's Personal Protective Equipment Standard (29 CFR 1910.132-138). This standard is intended to protect individuals from the risk of injury by creating a barrier against workplace hazards. This article provides guidelines for establishing PPE programs with an overview of the responsibilities for employers, supervisors, and employees, assessing hazards associated with thermal spray operations, and training workers about PPE, as well as guidelines for selecting, using, and maintaining PPE. It presents an overview of eye, face, head, hand, foot, hearing, fall, and respiratory protection. Respiratory and hearing protection should be used in conjunction with industrial hygiene monitoring.

This article discusses several aspects of biocompatibility of polymers, including the selection of a suitable polymer, specific use of a material, contact of polymer on body site, and duration of the contact. It describes the factors influencing the biological response of the polymer from a biocompatibility perspective. These include raw materials, the manufacturing process, cleaning and sterilization processes, and biodegradation and biostability. The article reviews the general testing methods of polymers, such as chemical, mechanical and thermal. It concludes with a section on the guidance, provided by the regulatory authorities, on the biocompatibility testing of polymers and polymer-containing devices that can aid in selecting the right analysis.

This article focuses on the analysis of materials and mechanical- (or biomechanical-) based medical device failures. It reviews the failure analysis practices, including evidence receipt, cleaning, nondestructive examination, destructive examination, exemplars analysis, and device redesign. The article examines the common failure modes, such as overload, fatigue, corrosion, hydrogen embrittlement, and fretting, of medical devices. The failure analysis of orthopedic implants, such as permanent prostheses and internal fixation devices, is described. The article reviews the failure mechanisms in some of the more common medical device materials, namely, stainless steels, titanium alloys, cobalt-base alloys, and nitinol. It presents case histories with examples for failure analysis.

High-pressure die casting is a fast method for the net shape manufacturing of parts from nonferrous alloys. This article reviews the automation technologies for the different stages or steps of the process. These steps include liquid metal pouring, injection, solidification, die open, part extraction, die lubrication, insert loading, and die close. Some manual aspects of the operations, together with automation options, are discussed. The article describes finishing steps, such as finish trimming, detailed deflashing, shot blast cleaning, and quality checks. Automation of the postcasting process is also discussed.

After solidification and cooling, further processing and finishing of the castings are required. This article describes the general operations of shakeout, grinding, cleaning, and inspection of castings, with particular emphasis on automation technology. It illustrates the vertical core knockout machine and the A-frame core knockout machine and lists the advantages and disadvantages of these machines. The article describes the general factors in automated or manual gate removal process. It concludes with discussion on the various types of inspection, such as the liquid penetrant inspection, pressure testing, radiographic inspection, magnetic particle inspection, and ultrasonic inspection.

The high-temperature corrosion processes that are most frequently responsible for the degradation of furnace accessories are oxidation, carburization, decarburization, sulfidation, molten-salt corrosion, and molten-metal corrosion. This article discusses each corrosion process, along with the corrosion behavior of important engineering alloys. It describes the corrosion of plating, anodizing, and parts of pickling equipment such as tanks, wirings and bus bars, racks, anode splines, pumps, and heaters.

This article describes the eight chemical cleaning methods, namely, circulation, fill and soak, cascade, foam, vapor-phase organic, steam-injected, on-line chemical, and mechanical cleaning. It presents information on deposit types, solvents used to remove them, and construction material incompatibilities in a table. The article summarizes the uses of chemical cleaning solutions, including hydrochloric acid, phosphoric acid, and sulfamic acid, as well as the additives used to neutralize their impact on corrosion. It discusses the chemical cleaning procedures, including selection of cleaning method and solvent, documentation of cleaning, and corrosion monitoring in chemical cleaning.

This article begins with discussion on forgeability and the factors affecting the forgeability of aluminum and aluminum alloys. It describes the types of forging methods and equipment and reviews critical elements in the overall aluminum forging process: die materials, die design, and die manufacture. The article discusses the critical aspects of various manufacturing elements of aluminum alloy forging, including the preparation of the forging stock, preheating stock, die heating, lubrication, trimming, forming and repair, cleaning, heat treatment, and inspection. It concludes with a discussion on the forging of advanced aluminum materials and aluminum alloy precision forgings.