This article provides a general technical description of thermal spray coatings used for corrosion protection in atmospheric and aqueous environments. It further discusses two basic coating approaches of corrosion protection, namely, the sacrificial coating of thermal spray aluminum (TSA) and thermal spray zinc (TSZ), and the barrier-type coating of corrosion-resistant materials. The emphasis is on sacrificial coatings. The article describes the steps involved in the application of TSA and TSZ: surface preparation, coating deposition, and postspray treatment. It discusses their field exposure tests and application history. The article also contains helpful information on the dense barrier coatings by high-velocity spraying processes along with their corrosion performance.

The rate and form of corrosion that occur in a particular situation depend on many complex variables. This article discusses the rate of corrosion of lead in natural and domestic water depending on the degree of water hardness caused by calcium and magnesium salts. Lead exhibits consistent durability in all types of atmospheric exposure, including industrial, rural, and marine. The article tabulates the corrosion of lead in various natural outdoor atmospheres and the corrosion of lead alloys in various soils. It explains the factors that influence in initiating or accelerating corrosion: galvanic coupling, differential aeration, alkalinity, and stray currents. The resistance of lead and lead alloys to corrosion by a wide variety of chemicals is attributed to the polarization of local anodes caused by the formation of a relatively insoluble surface film of lead corrosion products. The article also provides information on the corrosion rate of lead in chemical environments.

Vacuum heat treating consists of thermally treating metals and alloys in cylindrical steel chambers that have been pumped down to less than normal atmospheric pressure. This article provides a detailed account of the operations and designs of vacuum furnaces, discussing their pressure levels, resistance heating elements, quenching systems, work load support, pumping systems, and temperature control systems. It describes the classification of instruments used for measuring and recording pressure inside a vacuum processing chamber. Common devices include hydrostatic measuring devices and devices for measuring thermal and electrical conductivity. The article also describes the applications of the vacuum heat treating process, namely, vacuum nitriding and vacuum carburizing. Finally, it reviews the heat treating process of tool steels, stainless steels, Inconel 718, and titanium and its alloys.

This article provides a detailed discussion on the types of furnace atmospheres required for heat treating. These include generated exothermic-based atmospheres, generated endothermic-based atmospheres, generated exothermic-endothermic-based atmospheres, generated dissociated-ammonia-based atmospheres, industrial gas nitrogen-base atmospheres, argon atmospheres, and hydrogen atmospheres. Atmospheres for backfilling, partial pressure operation, and quenching in vacuum are also discussed. Furnace atmospheres constitute four major groups of safety hazards in heat treating: fire, explosion, toxicity, and asphyxiation. The article reviews the fundamentals of principal gases and vapors. It describes how the evaluation of the atmospheric requirements of heat treating furnaces is influenced by factors such as cost of operation and capital investment.

Weathering steels contain deliberate additions of alloying elements intended to increase the atmospheric corrosion resistance of steel. This article provides an overview of atmospheric corrosion testing. It describes the estimation of the atmospheric corrosion behavior of weathering steels by two methods such as short-term exposure tests and calculation of a corrosion index based on the steel composition. The article highlights some generalities about corrosion mechanisms. Based on the mechanism of atmospheric corrosion resistance of weathering steel, working rules for creating the protective oxide film have evolved. The article also provides case histories that illustrate both the violations of these rules and suggestions on how to avoid certain maintenance problems that may be encountered with weathering steels.

Carbon and low-alloy steels are considered resistant only to very mild corrosives, while the various high-alloy grades are applicable for varying situations from mild to severe services, depending on the particular conditions involved. This article describes the factors that must be considered, by alloy casting users, in material selection. It presents compositions of cast steels tested in atmospheric corrosion in a tabular form. The rate of corrosion of a material in an environment can generally be estimated with confidence only from long-term tests. The article graphically presents the results of a research program that compared the corrosion resistance of nine cast steels in marine and industrial atmospheres. It illustrates the comparison of corrosion rates of cast steels, malleable cast iron, and wrought steel after 3 years of exposure in two atmospheres and provides the conclusions drawn from these tests.

This article reviews general corrosion of uranium and its alloys under atmospheric and aqueous exposure as well as with gaseous environments. It describes the dependence of uranium and uranium alloy corrosion on microstructure, alloying, solution chemistry, and temperature as well as galvanic interactions between uranium, its alloys, and other metals. The article provides information on the atmospheric corrosion of uranium based on oxidation in dry air or oxygen, water vapor, and oxygen-water vapor mixtures depending upon particular storage conditions. The mechanism and morphology of hydride corrosion of uranium are discussed. The article provides information on environmentally assisted cracking, protective coatings, and surface modification of uranium and its alloys. It also summarizes the environmental, safety, and health considerations for their use.

Tensile testing of fiber-reinforced composite materials is performed to determine uniaxial tensile strength, Young’s modulus, and Poisson’s ratio relative to principal material directions, and helps in the prediction of the properties of laminates. Beginning with an overview of the fundamentals of tensile testing of fiber-reinforced composites, this article describes environmental exposures that can occur during specimen preparation and testing. These include exposures during specimen preparation, and planned exposure such as moisture, damage (impact), and thermal cycling. The article also discusses the test methods of the four major types of mechanical testing of polymer-matrix composites: tensile, compression, flexural, and shear.

Control of temperature and furnace atmospheres has become increasingly critical to successful heat treating. Temperature instrumentation and control systems used in heat treating include temperature sensors, controllers, final control elements, measurement instruments, and set-point programmers. This article describes these items and discusses the classifications and control of furnace atmospheres. The article also describes the surface carbon control devices available for the wide variety of furnace atmospheres and evaluation of carbon control. Finally, the article provides a set of guidelines for safety procedures that are common to all industrial heat treating furnace installations.

Independent verification of coating system performance can be based on laboratory testing and/or field exposure. Qualification testing is a critical component to coating system selection. This article focuses on performance evaluations that are used to prequalify coating systems, namely, facility-specific, industry-specific, coating-type-specific, or a combination of these. It describes the standard laboratory tests used to generate performance data, namely, physical, compositional, chemical exposure, and application characteristics tests. The pros and cons of using manufacturer-generated data versus independently generated data are discussed. The article provides information on accelerated corrosion/weathering testing and nuclear level 1/level 2 service coatings qualification. It also describes the procedures for establishing minimum performance requirements and for determining when requalification testing may be required.

Heat treating involves the use of fuel gases for heating and gases in the furnace atmosphere. This article describes the hazards associated with furnace atmospheres and the related safety considerations. It discusses the effect of fuel on combustion efficiency. The article also contains tables that provide information on the physical, thermal and combustion properties of common gases and liquids, and the heat content of various gases.

This article provides information on the Unified Numbering System designations and temper designations of copper and copper alloys. It discusses the basic types of heat treating processes of copper and copper alloys, namely, homogenizing, annealing, and stress relieving, and hardening treatments such as precipitation hardening, spinodal hardening, order hardening, and quench hardening and tempering. The article presents tables that list the compositions and mechanical properties of copper alloys. It also discusses two strengthening mechanisms of copper alloys, solid-solution strengthening and work hardening. Finally, the article provides information on the equipment used for the heat treating of copper and copper alloys, including batch-type atmosphere furnaces, continuous atmosphere furnaces, and salt baths.

Dross, which is the oxide-rich surface that forms on melts due to exposure to air, is a term that is usually applied to nonferrous melts, specifically the lighter alloys such as aluminum or magnesium. This article describes dross formation, economic implications of dross, in-plant enhancement or recovery of dross, and ways to reduce dross formation. It discusses the influence of melter type on dross generation and the influence of charge materials and operating practices on melt loss. Fluxing is a word applied in a broad sense to a number of melt treating methods. The article discusses in-furnace treatment with chemical fluxes.

This article discusses the occupational health hazards related to industrial protective coating application and removal. It explains the health hazards associated with coating constituents such as lead, cadmium, chromium, arsenic, silica, and asbestos. The article also discusses hazard evaluation, hazard controls, Occupational Safety and Health Administration standards, and industry consensus standards. It concludes with a description of containment systems to prevent environmental exposures from industrial paint removal projects.

Tantalum is one of the most versatile corrosion-resistant metals known. The outstanding corrosion resistance and inertness of tantalum are attributed to a very thin, impervious, protective oxide film that forms on exposure of the metal to slightly anodic or oxidizing conditions. This article provides a discussion on the mechanism of corrosion resistance and on the behavior of tantalum in different corrosive environments, namely, acids; salts; organic compounds; reagents, foods, and pharmaceuticals; body fluids and tissues; and gases. It contains several tables that summarize the effects of acids, salts, and miscellaneous corrosive reagents on tantalum and applications for tantalum equipment in chemical, pharmaceutical, and other industries. Finally, the article presents a discussion on hydrogen embrittlement, the galvanic effects, and cathodic protection of tantalum and describes the corrosion resistance of different types of tantalum-base alloys.

Superalloys are nickel, iron-nickel, and cobalt-base alloys generally used for high-temperature applications. Superalloys are used in aircraft, industrial, marine gas turbines, nuclear reactors, spacecraft structures, petrochemical production, orthopedic and dental prostheses, and environmental protection applications. This article discusses the material characteristics, phases, structures, and systems of superalloys. It describes the processing of superalloys, including primary and secondary melting, deformation processing (conversion), powder processing, investment casting, and joining methods. The article also describes the properties, microstructure, and thermal exposure of superalloys. It further discusses the effects of environmental factors on superalloys, including oxidation and hot corrosion. Protective coatings are also discussed. The article provides information on the mechanical properties and chemical composition of nickel, iron, and cobalt-base superalloys in both the cast and wrought forms.

Film radiography requires the development of the exposed film so that the latent image becomes visible for viewing. It describes the general characteristics of film, including speed, gradient, and graininess, and the factors affecting film selection and exposure time. The article discusses the three major inspection techniques for tubular sections, namely, the double-wall, double-image technique; the double-wall, single-image technique; and the single-wall, single-image technique. It illustrates the arrangements of penetrameters and identification markers for the radiography of plates, cylinders, and flanges. The article discusses various control methods, including the use of lead screens; protection against backscatter and scatter from external objects; and the use of masks, diaphragms, collimators, and filtration. The radiographic appearance of specific types of flaws is also discussed. The article concludes with a discussion on two methods of radiographic film processing: manual and automatic processing.

This article summarizes the Sendzimir process, the Cook-Norteman process, the coating types, composition, characteristics, and typical applications of various metallic coatings, such as zinc, aluminum, zinc-aluminum alloy, and aluminum-zinc alloy coatings. It provides a discussion on aqueous corrosion and atmospheric corrosion of galvanized steel and aluminized steel, as well as the intergranular corrosion of galvanized steel.

This article discusses the environmental factors and kinetics of atmospheric corrosion, aqueous corrosion, and soil corrosion of carbon steels. It also provides information on corrosion in concrete and steel boilers.

This article describes the allotropic modification and atmospheric corrosion of pure tin. Corrosion of pure tin due to oxidation reaction, and reaction with the other gases, water, acids, bases, and other liquid media, is discussed. The article provides information on corrosion behavior on soft solders, pewter, bearing alloys, tin-copper alloys, and tin-silver alloys. It reviews the influence of corrosion on immersion tin coating, tin-cadmium alloy coatings, tin-cobalt coatings, tin-copper coatings, tin-lead coatings, tin-nickel coatings, and tin-zinc coatings. The general properties and corrosion resistance of tinplate are summarized. The article also describes the methods of corrosion testing of coatings; these include an analysis of coating thickness measurements, porosity and rust resistance testing, solderability test, and specific special tests.