When metal is exposed to an oxidizing gas at elevated temperature, corrosion can occur by direct reaction with the gas, without the need for the presence of a liquid electrolyte. This type of corrosion is referred to as high-temperature gaseous corrosion. This article describes the various forms of high-temperature gaseous corrosion, namely, high-temperature oxidation, sulfidation, carburization, corrosion by hydrogen, and hot corrosion.

This article provides information on the thermodynamics and kinetics of high-temperature corrosion. The thermodynamics of high-temperature corrosion reactions reveals what reactions are possible under certain conditions and kinetics explains how fast these possible reactions will proceed. The article describes the diffusion process that plays a key role in oxidation and other gaseous reactions with metals. It discusses the development of stress in oxide layers. The article presents the sample preparation methods for high-temperature testing, and expounds the measurement methods of high-temperature degradation. It reviews a number of potential processes, which are responsible for high-temperature corrosion. The article details a wide range of coatings and coating processes for protecting components in a variety of operating conditions. It also discusses the testing methods used for materials at high temperatures, including furnace tests, burner rig testing, and thermogravimetric analysis, and the test methods conducted at high temperature and high pressure.

This article examines the characteristics and behavior of scale produced by various types of oxidation. The basic models, concepts, processes, and open questions for high-temperature gaseous corrosion are presented. The article describes the development of geometrically induced growth stresses, transformation stresses, and thermal stresses in oxide scales. It discusses the ways in which stresses can be relieved. The article provides information on catastrophic oxidation, internal oxidation, sulfidation, alloy oxidation, selective oxidation, and concurrent oxidation. It illustrates the relationships between scale morphologies on binary alloys and concludes with a discussion on metal dusting and chlorine corrosion.

This article provides an introduction to the fundamentals of corrosion in gases. It tabulates the structures and properties of oxides as well as the physical properties of pure metals.

This article provides a summary of the concepts discussed in the articles under the Section “Fundamentals of Corrosion” in ASM Handbook, Volume 13A: Corrosion: Fundamentals, Testing, and Protection. In this section, the thermodynamic aspects of corrosion are descried first followed by a group of articles discussing the fundamentals of aqueous corrosion kinetics. The fundamentals of gaseous corrosion are addressed next. The fundamental electrochemical reactions of corrosion and their uses are finally described.

This article is a pictorial guide to forms of corrosion that draws attention to common pitfalls or situations that have caused premature corrosion, sometimes with expensive consequences. The examples used are not exhaustive; they highlight the necessity to fully examine materials, conditions, and specific circumstances that together can reduce the anticipated service life of a component or plant. The color images in this article are categorized according to the type of corrosion following the general order that is adopted in Volume 13A of ASM Handbook. The first table of the article provides a categorization of the forms of corrosion. It also provides a reference to articles or sections of articles in Volume 13A that detail the particular corrosion form or mechanism. The second table is a guide listing the figures in this article by material and by the corrosion form or mechanism illustrated.

This article discusses two approaches for determining gaseous corrosion rates, one based on indirect (discontinuous) measurements, the other based on direct (continuous) measurements. It explains how corrosion rate data can be obtained indirectly by measuring scale thickness, scale weight per unit surface area, loss of metal thickness, loss of material weight per unit surface area, or weight change of oxidant bonded in the scale per unit surface area as a function of time. It also describes several continuous methods, including volumetric measurements, the manometric method, and thermogravimetric analysis, and the conditions under which they can be used.

High-temperature exposure of materials occurs in many applications such as power plants (coal, oil, natural gas, and nuclear), land-based gas turbine and diesel engines, gas turbine engines for aircraft, marine gas turbine engines for shipboard use, waste incineration, high-temperature fuel cells, and missile components. This article discusses high-temperature corrosion in boilers, diesel engines, gas turbines, and waste incinerators. Boilers are affected by stress rupture failures, waterside corrosion failures, fireside corrosion failures, and environmental cracking failures. Contamination of combustion fuel in diesel engines can cause high-temperature corrosion. Gas turbine engines are affected by hot corrosion. Refractory-lined incinerators and alloy-lined incinerators are discussed. The article provides case studies for each component failure.

Corrosion is classified into two categories: corrosion that is not influenced by any other process and corrosion that is influenced by another process such as the presence of stresses or erosion. This article discusses uniform corrosion, localized corrosion, metallurgically influenced corrosion, and microbiologically influenced corrosion, which fit under the classification of corrosion that is not influenced by any outside process. It also explains mechanically assisted degradation and environmentally induced cracking, which fit under the classification of corrosion that is influenced by an outside process.

High temperature corrosion may occur in numerous environments and is affected by factors such as temperature, alloy or protective coating composition, time, and gas composition. This article explains a number of potential degradation processes, namely, oxidation, carburization and metal dusting, sulfidation, hot corrosion, chloridation, hydrogen interactions, molten metals, molten salts, and aging reactions including sensitization, stress-corrosion cracking, and corrosion fatigue. It concludes with a discussion on various protective coatings, such as aluminide coatings, overlay coatings, thermal barrier coatings, and ceramic coatings.

Low-temperature surface hardening is mostly applied to austenitic stainless steels when a combination of excellent corrosion performance and wear performance is required. This article provides a brief history of low-temperature surface hardening of stainless steel, followed by a discussion on physical metallurgy, including crystallographic identity, thermal stability and decomposition, nitrogen and carbon solubility in expanded austenite, and diffusion kinetics of interstitials. It provides a description of low-temperature nitriding and nitrocarburizing processes for primarily austenitic and, to a lesser extent, other types of stainless steels along with practical examples and industrial applications of these steels.

Understanding the high-temperature corrosion behavior of alloys is an important step toward the selection of appropriate alloys for process equipment. This article briefly describes the high-temperature corrosion modes that are frequently encountered in the chemical process industry. These modes include oxidation, carburization, metal dusting, nitridation, halogen corrosion, and sulfidation.

Nitriding is a general term for all processes based on the addition of nitrogen to the surface of steel. When carbon is added along with the nitrogen, the process is called nitrocarburizing. This article provides a detailed discussion on the functional and structural properties of nitrided layers. It describes the structural changes on the surface of carbon steels, alloy steels, and austenitic stainless steels. The article explains the effects of the various nitriding processes, namely, gaseous nitriding, plasma nitriding, gaseous nitrocarburizing, and salt bath nitrocarburizing, on the structure and properties of nitrided layers.

This article provides a discussion on the mechanisms of wear and their interactions with gaseous corrosion. The wear mechanisms include abrasive, erosive, fretting, and sliding. The measurement of degradation on combustion walls in coal-fired boilers is discussed. The article concludes with information on the common coating techniques used for wear-corrosion control.

Metals can react chemically with oxygen when exposed to air. Essential to an understanding of the gaseous corrosion of a metal are the crystal structure and the molar volume of the metal on which the oxide builds, both of which may affect growth stresses in the oxide. This article presents crystal structures and thermal properties of pure metals and oxides in a tabular form. The free energy of reaction, which describes the oxidation process of a pure divalent metal, is presented. The article illustrates the Richardson-Jeffes diagram, which is used in the determination of the standard Gibbs energy change of formation of oxides and the corresponding dissociation pressures of the oxides as a function of temperature. It demonstrates the Kellogg diagram which shows stability range in more complicated multioxidant systems. The article explains the determination of partial pressures of gas mixtures and partial pressures of volatile oxidation products.

This article describes the corrosion modes in a waste-to-energy boiler. It discusses the corrosion protection and alloy performance with an emphasis on two main areas of the boiler: furnace water walls and super heaters.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.

Ammonia and ammonium hydroxide are not particularly corrosive in themselves, but corrosion problems can arise with specific materials, particularly when contaminants are present. This article discusses the corrosion resistance of materials used for the manufacture, handling, and storage of ammonia. These materials include aluminum alloys, iron and steel, stainless steels, nickel and its alloys, copper and its alloys, titanium and its alloys, zirconium and its alloys, niobium, tantalum, and nonmetallic materials.

This article provides an overview of the classification of hydrogen damage. Some specific types of the damage are hydrogen embrittlement, hydrogen-induced blistering, cracking from precipitation of internal hydrogen, hydrogen attack, and cracking from hydride formation. The article focuses on the types of hydrogen embrittlement that occur in all the major commercial metal and alloy systems, including stainless steels, nickel-base alloys, aluminum and aluminum alloys, titanium and titanium alloys, copper and copper alloys, and transition and refractory metals. The specific types of hydrogen embrittlement discussed include internal reversible hydrogen embrittlement, hydrogen environment embrittlement, and hydrogen reaction embrittlement. The article describes preservice and early-service fractures of commodity-grade steel components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also reviewed.

The primary fossil fuels are generally defined as coal, oil, natural gas, tar sands, and shale oil. This article discusses the characteristics and the types of fuels used in fossil and fuel industries. It describes the energy conversion in fuels and outlines the efficiency of a heat engine with the help of the Carnot equation.