Dew-point corrosion occurs when gas is cooled below the saturation temperature pertinent to the concentration of condensable species contained by a gas. This article discusses dew-point corrosion problems in the susceptible areas of dry flue gas handling systems. The corrosion problems associated with the nitrate stress-corrosion cracking in heat-recovery steam generators are also discussed. The article presents general comments on the materials selection; plant operation; use of neutralizing additives; and maintenance, good housekeeping, and lagging (insulation). It concludes with information on guidance for maintaining specific sections of the plant.

Stress-corrosion cracking (SCC) is a form of corrosion and produces wastage in that the stress-corrosion cracks penetrate the cross-sectional thickness of a component over time and deteriorate its mechanical strength. Although there are factors common among the different forms of environmentally induced cracking, this article deals only with SCC of metallic components. It begins by presenting terminology and background of SCC. Then, the general characteristics of SCC and the development of conditions for SCC as well as the stages of SCC are covered. The article provides a brief overview of proposed SCC propagation mechanisms. It discusses the processes involved in diagnosing SCC and the prevention and mitigation of SCC. Several engineering alloys are discussed with respect to their susceptibility to SCC. This includes a description of some of the environmental and metallurgical conditions commonly associated with the development of SCC, although not all, and numerous case studies.

This article commences with a discussion on the characteristics of stress-corrosion cracking (SCC) and describes crack initiation and propagation during SCC. It reviews the various mechanisms of SCC and addresses electrochemical and stress-sorption theories. The article explains the SCC, which occurs due to welding, metalworking process, and stress concentration, including options for investigation and corrective measures. It describes the sources of stresses in service and the effect of composition and metal structure on the susceptibility of SCC. The article provides information on specific ions and substances, service environments, and preservice environments responsible for SCC. It details the analysis of SCC failures, which include on-site examination, sampling, observation of fracture surface characteristics, macroscopic examination, microscopic examination, chemical analysis, metallographic analysis, and simulated-service tests. It provides case studies for the analysis of SCC service failures and their occurrence in steels, stainless steels, and commercial alloys of aluminum, copper, magnesium, and titanium.

This article addresses the long-term corrosion behavior of high-level waste (HLW) container materials, more specifically of the outer shell of the containers. It discusses time, environmental, and materials considerations for the emplacement of HLW in geological repositories. Environmental corrosion resistance of materials planned for reducing repositories is also discussed. The article reviews the design and characterization of nuclear waste repository with an oxidizing environment surrounding the waste package.

This article describes the incubation, nucleation, and propagation of stress-corrosion cracking and how to evaluate it using standard tests. It discusses constant-strain, constant-load, bending, and uniaxial tension testing and how they compare when evaluating smooth and precracked test specimens under elastic-strain, plastic-strain, and residual-stress conditions. The article provides guidance on specimen selection and preparation, strain rate, and test equipment. It also examines service and laboratory test environments and provides detailed information on how to test various steels and alloys and how to interpret test results.

This article summarizes the metallurgy of carbon and alloy steels, followed by discussions on their major mechanical properties, namely, static fracture toughness, dynamic fracture toughness, fatigue or sustained-load crack growth rates, and fatigue or sustained-load thresholds. It addresses fatigue crack propagation and sustained-load crack propagation, as well as the fundamental aspects of fracture in steels. The article illustrates the effects of variations in the alloy chemistry, microstructure, temperature, strain rate, and environment on various fracture toughness or crack growth rate parameters.

Stress-corrosion cracking (SCC) is a phenomenon in which time-dependent crack growth occurs when the necessary electrochemical, mechanical, and metallurgical conditions exist. This article provides an overview of the environmental phenomenon, mechanisms, and controlling parameters of SCC. It describes the phenomenological and mechanistic aspects of the initiation and propagation of SCC. The article includes a phenomenological description of crack initiation and propagation that describes well-established experimental evidence and observations of stress corrosion. Discussions on mechanisms describe the physical process involved in crack initiation and propagation. The article also includes information on dissolution models and mechanical fracture models.

This article discusses the five basic matrix structures in cast irons: ferrite, pearlite, bainite, martensite, and austenite. The alloying elements, used to enhance the corrosion resistance of cast irons, including silicon, nickel, chromium, copper, molybdenum, vanadium, and titanium, are reviewed. The article provides information on classes of the cast irons based on corrosion resistance. It describes the various forms of corrosion in cast irons, including graphitic corrosion, fretting corrosion, pitting and crevice corrosion, intergranular attack, erosion-corrosion, microbiologically induced corrosion, and stress-corrosion cracking. The cast irons suitable for the common corrosive environments are also discussed. The article reviews the coatings used on cast irons to enhance corrosion resistance, such as metallic, organic, conversion, and enamel coatings. It explains the basic parameters to be considered before selecting the cast irons for corrosion services.

Stress-corrosion cracking (SCC) is a cracking phenomenon that occurs in susceptible alloys, and is caused by the conjoint action of tensile stress and the presence of a specific corrosive environment. This article provides an overview of the anodic dissolution mechanisms and cathodic mechanisms for SCC. It discusses the materials, environmental, and mechanical factors that control hydrogen embrittlement and SCC behavior of different engineering materials with emphasis on carbon and low-alloy steels, high-strength steels, stainless steels, nickel-base alloys, aluminum alloys, and titanium alloys.

Corrosion of carbon steel weldments can be due to metallurgical effects, such as preferential corrosion of the heat-affected zone (HAZ) or weld metal, or it can be associated with geometrical aspects, such as stress concentration at the weld toe, or creation of crevices due to joint design. This article describes the issues related to corrosion of carbon steel weldments and the remedial measures that have proven to be successful in specific cases. It provides useful information on preferential HAZ corrosion, preferential weld metal corrosion, and galvanic corrosion.

Cast irons provide excellent resistance to a wide range of corrosion environments when properly matched with that service environment. This article presents basic parameters to be considered before selecting cast irons for corrosion services. Alloying elements can play a dominant role in the susceptibility of cast irons to corrosion attack. The article discusses the various alloying elements, such as silicon, nickel, chromium, copper, and molybdenum, that enhance the corrosion resistance of cast irons. Cast irons exhibit the same general forms of corrosion as other metals and alloys. The article reviews the various forms of corrosions, such as graphitic corrosion, fretting corrosion, pitting and crevice corrosion, intergranular attack, erosion-corrosion, microbiologically induced corrosion, and stress-corrosion cracking. It discusses the four general categories of coatings used on cast irons to enhance corrosion resistance: metallic, organic, conversion, and enamel coatings.

This article describes the four major conditions that can cause beryllium to corrode in air. These include beryllium carbide particles exposed at the surface; surface contaminated with halide, sulfate, or nitrate ions; surface contaminated with other electrolyte fluids; and atmosphere that contains halide, sulfate, or nitrate ions. The article provides information on the behavior of beryllium under the combined effects of high-purity water environment, stress and chemical environment, and high-temperature environment. The compositions of the structural grades for intentionally controlled elements and major impurities are tabulated. The article discusses the in-process problems and procedures that are common but avoidable when processing beryllium and aluminum-beryllium composites. It also describes the types of coatings used on beryllium and aluminum-beryllium. These include chemical conversion coatings, anodized coatings, plated coatings, organic coatings, and plasma-sprayed coatings.

Mechanically assisted degradation of metals is defined as any type of degradation that involves a corrosion mechanism and a wear or fatigue mechanism. This article provides a discussion on the mechanisms of five forms of degradation: erosion, fretting corrosion, fretting fatigue, cavitation and water drop impingement, and corrosion fatigue. It describes the factors affecting the severity of fretting corrosion. The article also illustrates the relationship between corrosion fatigue and stress-corrosion cracking.

This article briefly describes water and steam chemistry, which influence the effect of corrosion in boilers. The appropriate control measures to prevent corrosion in boilers are also presented. The article provides a discussion on the common causes of fluid-side corrosion such as flow-accelerated corrosion, oxygen pitting, chelant corrosion, caustic corrosion, acid corrosion, organic corrosion, phosphate corrosion, hydrogen damage, and corrosion-assisted cracking.

This article discusses the identifying characteristics of the forms or mechanisms of corrosion that commonly attack copper metals, as well as the most effective means of combating each. It tabulates the corrosion ratings of wrought copper alloys in various corrosive media. The article describes the corrosion behavior of copper alloys in specific environments. It reviews the corrosion characteristics of copper and copper alloys in various acids, alkalis, salts, organic compounds, and gases. The article provides information on the behavior of copper alloys that is susceptible to stress-corrosion cracking in various industrial and chemical environments. It concludes with information on various corrosion testing methods, including aqueous corrosion testing, dynamic corrosion tests, and stress-corrosion testing.

This article focuses on the effects of process variables on corrosion of metals in processing plants: plant environments; startup, shutdown, and downtime conditions; and seasonal temperature changes. It also tabulates the effects of process variables on corrosion of metals in aggressive environments.

This article illustrates the use of the American Petroleum Institute (API) 579-1/ASME FFS-1 fitness-for-service (FFS) code (2020) to assess the serviceability and remaining life of a corroded flare knockout drum from an oil refinery, two fractionator columns affected by corrosion under insulation in an organic sulfur environment, and an equalization tank with localized corrosion in the shell courses in a chemicals facility. In the first two cases, remaining life is assessed by determining the minimum thickness required to operate the corroded equipment. The first is based on a Level 2 FFS assessment, while the second involves a Level 3 assessment. The last case involves several FFS assessments to evaluate localized corrosion in which remaining life was assessed by determining the minimum required thickness using the concept of remaining strength factor for groove-like damage and evaluating crack-like flaws using the failure assessment diagram. Need for caution in predicting remaining life due to corrosion is also covered.

Exfoliation is a structure-dependent form of localized intergranular corrosion that follows grain boundaries in the rolling direction of wrought materials, particularly aluminum alloys. Highly cold-worked materials with elongated grain boundaries tend to be most affected. The article provides information on accelerated salt spray and total-immersion testing methods to help rate the exfoliation corrosion susceptibility of various aluminum alloys and alloy compositions. It also discusses visual assessment challenges and identifies several ASTM designations and where and how they apply.