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 describes the control of water chemistry in the steam cycle of a power plant for achieving corrosion control, deposition prevention, and higher cycle efficiency. It discusses the materials requirements of the components exposed to supercritical water in supercritical (SC) and ultrasupercritical (USC) power plants. These components include high-pressure steam piping and headers, superheater and reheater tubing, water wall tubing in the boiler, high-and intermediate-pressure rotors, rotating blades, and bolts in the turbine section. The article reviews the boiler alloys, used in SC and USC boilers, such as ferritic steels, austenitic steels, and nickel-base alloys. It provides information on the materials used in turbine applications such as ferritic rotor steels, turbine blade alloys, and bolting materials. The article explains various factors influencing steamside corrosion in SC power plants. It also deals with the role of overall efficiency in the USC power generation.

Failures in boilers and other equipment taking place in power plants that use steam as the working fluid are discussed in this article. The discussion is mainly concerned with failures in Rankine cycle systems that use fossil fuels as the primary heat source. The general procedure and techniques followed in failure investigation of boilers and related equipment are discussed. The article is framed with an objective to provide systematic information on various damage mechanisms leading to the failure of boiler tubes, headers, and drums, supplemented by representative case studies for a greater understanding of the respective damage mechanism.

This article explains the main types and characteristic causes of failures in boilers and other equipment in stationary and marine power plants that use steam as the working fluid with examples. It focuses on the distinctive features of each type that enable the failure analyst to determine the cause and suggest corrective action. The causes of failures include tube rupture, corrosion or scaling, fatigue, erosion, and stress-corrosion cracking. The article also describes the procedures for conducting a failure analysis.

The steam turbine is the simplest and most efficient engine for converting large amounts of heat energy into mechanical work. This article discusses the primary corrosion mechanisms such as corrosion fatigue, stress-corrosion cracking (SCC), pitting, corrosion, and erosion-corrosion, in steam turbines. It illustrates the various causes of the corrosiveness of the steam turbine environments through a Mollier diagram. The article describes the four parts of design disciplines that affect turbine corrosion, namely, mechanical design, heat transfer, flow and thermodynamics, and physical shape. It lists the ways to control the steam and surface chemistry, and design and material improvements to minimize turbine corrosion.

The presence of certain impurities in coal and oil is responsible for the majority of fireside corrosion experienced in utility boilers. In coal, the primary impurities are sulfur, alkali metals, and chlorine. The most detrimental impurities in fuel oil are vanadium, sodium, sulfur, and chlorine. This article describes the two categories of fireside corrosion based on location in the furnace: waterwall corrosion in the lower furnace and fuel ash corrosion of superheaters and reheaters in the upper furnace. It discusses prevention methods, including changes to operating parameters and application of protective cladding or coatings.

This article addresses the major heat-transfer components of the water-steam loop of a power plant. It describes the various types of condensers, including water-cooled condensers and air-cooled condensers. The article explains the corrosion mechanisms encountered in the condensers, including erosion-corrosion, galvanic corrosion, and pitting corrosion. It discusses the types of deaerators and deals with their corrosion problems. The article provides a discussion on two types of feedwater heaters: channel feedwater heaters and header feedwater heaters. It summarizes the corrosion problems associated with common feedwater heater tube materials.

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.

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.

This article discusses the methods of pulp production, pulp processing, pulp bleaching, and paper manufacturing. It describes various types of digesters, their construction materials, the corrosion problems encountered, and methods to protect these digesters from corrosion. The article examines the corrosion problems in high-yield mechanical pulping, sulfite process, neutral sulfite semichemical pulping, chemical recovery, tall oil plants, wastewater treatment, and recovery boilers. It explains the stages of chlorine-based and nonchlorine bleaching, process water reuse for elemental chlorine-free and nonchlorine bleaching stages, selection of material for bleaching equipment, developments in oxygen bleaching, and the use of highly corrosion-resistant materials for bleach plant equipment. The article reviews the materials used in the construction of paper machine components and specific corrosion problems that affect them. It discusses the composition and corrosive nature of white water. The article also addresses the corrosion and chemical recovery associated with kraft pulping liquors.

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 discusses some elevated-temperature properties of carbon steels and low-alloy steels with ferrite-pearlite and ferrite-bainite microstructures for use in boiler tubes, pressure vessels, and steam turbines. The selection of steels to be used at elevated temperatures generally involves compromise between the higher efficiencies obtained at higher operating temperatures and the cost of equipment, including materials, fabrication, replacement, and downtime costs. The article considers the low-alloy steels which are the creep-resistant steels with 0.5 to 1.0% Mo combined with 0.5 to 9.0% Cr and perhaps other carbide formers. The factors affecting mechanical properties of steels include the nature of strengthening mechanisms, the microstructure, the heat treatment, and the alloy composition. The article describes these factors, with particular emphasis on chromium-molybdenum steels used for elevated-temperature service. Although the mechanical properties establish the allowable design-stress levels, corrosion effects at elevated temperatures often set the maximum allowable service temperature of an alloy. The article also discusses the effects of alloying elements in annealed, normalized and tempered, and quenched and tempered steels.

This article is an atlas of fractographs that helps in understanding the causes and mechanisms of fracture of ASTM/ASME alloy steels and in identifying and interpreting the morphology of fracture surfaces. The fractographs illustrate the solidification cracking, creep failure, brittle fracture, fracture by overpressurization, inclusion effect, fatigue crack propagation, ductile fatigue striation, secondary cracking, intergranular fracture, and elevated-temperature fracture of alloy steels used in pressure vessels, steam boiler superheater tubes, and box-girder bridges.

The corrosion process that occurs in industrial systems is often difficult to discern until extensive deterioration has occurred. For boilers to function properly, the incoming water must be processed to meet the water quality required for the boiler. This article discusses pretreatment methods of the incoming water and preboiler corrosion protection methods. It analyzes internal treatment and condensate treatment of boilers. The article discusses three types of cooling systems: once-through systems, open recirculating systems, and closed recirculating systems. The corrosion processes which occur in water-recirculating systems and the effect of dissolved gases, temperature, pH, suspended solids, dissolved salts, and scale deposition on corrosivity of water, are also reviewed. The article also considers anodic and cathodic inhibitors and the control of corrosion in municipal water systems.

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.