Metals and ceramics exposed to high-temperature salt solutions are susceptible to a form of corrosion caused by fused salts accumulating on unprotected surfaces. This article examines the electrochemistry of such hot corrosion processes, focusing on sodium sulfate systems generated by the combustion of fossil fuels. It explains how salt chemistry, including acid/base and oxidizing properties, affects corrosion rates and mechanisms. The article also provides information on electrochemical testing and explains how Pourbaix methods, normally associated with aqueous corrosion, can be used to study fused-salt corrosion.

Soluble salts on a surface can affect a steel substrate or coating in two principal ways: corrosion acceleration and osmotic blistering. This article provides a detailed discussion on the mechanisms for each of these deleterious effects. It describes the most detrimental anions with regard to corrosion, namely, chlorides, sulfates, and nitrates, and provides information on recognition and testing of the presence of soluble salts. The salt-measurement techniques and commercially available equipment are also described. The article provides information on research regarding tolerable levels of salts beneath coatings. The information shows that there appears to be a threshold limit to the salt contamination that a given coating/coating system can tolerate in a given environment.

This article provides a detailed account of the various alkaline and acid plating baths used for electrolytic copper plating. Dilute cyanide and Rochelle cyanide baths, high-efficiency sodium and potassium cyanide baths, alkaline noncyanide copper plating baths, and alkaline copper pyrophosphate baths, are discussed. The article reviews acid plating baths such as copper sulfate bath and copper fluoborate bath. It also presents information on the surface preparation considerations, bath composition, and operating variables of copper plating as well as the equipment used.

Ion chromatography (IC) is an analytical technique that uses columns packed with ion exchange resins to separate ions in aqueous solutions and dynamically elute them to a detector. This article provides information on the different modes of detection, namely, eluent-suppressed conductivity detection, single-column ion chromatography with conductivity detection, ion chromatography with spectrophotometric detection, and amperometric electrochemical detection. It describes the modes of separation techniques in IC and reversed-phase IC. The article discusses the detection capabilities of IC, the procedures for preparing solid and liquid samples, as well as the applications of IC.

Copper can be electrodeposited from numerous electrolytes. Cyanide and pyrophosphate alkalines, along with sulfate and fluoborate acid baths, are the primary electrolytes used in copper plating. This article provides information on the chemical composition, plating baths, and operating conditions of electrodeposition processes for chromium plating, nickel plating, iron plating, cadmium plating, zinc plating, indium plating, lead plating, tin plating, silver plating, gold plating, brass plating, bronze plating, tin-lead plating, zinc-iron plating, and zinc-nickel plating. The article also discusses selective plating, electroforming, and other processes and where they are typically used.

This article presents a summary of the chemical fundamentals, general techniques, limitations, and applications of chemical spot testing as well as a brief overview of innovations and specialized applications. A list of selected reagents, including abbreviated instructions for preparing the reagent solution(s), for performing the spot test, and for interpreting the results, is also included. The article discusses two specialized applications of qualitative analysis, namely illicit drug identification and spacecraft drinking water quality testing. It also contains tables listing common presumptive tests for detecting anions and cations in aqueous solution.

A tin deposit provides sacrificial protection to copper, nickel, and many other nonferrous metals and alloys. Tin also provides good protection to steel. Tin can be deposited from either alkaline or acid electrolytes. This article explains the compositions and operating conditions of these electrolytes.

This article describes the steps, bath composition and characteristics, equipment, plating rate, deposit thickness, and applications for different types of nonelectrolytic deposition processes, including electroless nickel plating, electroless copper plating and mechanical plating.

This article characterizes the corrosion resistance of precious metals, namely, ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold. It provides a discussion on the general fabricability; atomic, structural, physical, and mechanical properties; oxidation and corrosion resistance; and corrosion applications of these precious metals. The article also tabulates the corrosion rates of these precious metals in corrosive environment, namely, acids, salts, and halogens.

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.

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.

This article provides information on basic chemical equilibria, wet analytical chemistry, and the appropriateness of classical wet methods. It focuses on nonoxidizing acids and oxidizing acids. The article includes information on the qualitative methods used to identify materials by wet chemical reaction. Gravimetry, in which a chemical species is weighed; titrimetry, which involves volume measurement of a liquid reactant; and a host of separation techniques, which require diverse forms of laboratory manipulation, are discussed. The article briefly describes the partitioning of oxidation states as well as those applications in surface studies and rapid material identification in which chemical techniques have proved useful.

This article presents information regarding the use of protective coatings in municipal potable water systems, including raw water collection and transmission, water treatment plants, and treated water distribution. It provides useful guidance for the selection and use of protective coatings in these municipal water systems. The most commonplace corrosion-damage mechanisms are highlighted. The article describes the most common materials of construction found in municipal water systems, namely, cast iron, ductile iron, carbon steel, precast concrete cylinder pipe and reinforced concrete pipe, prestressed concrete tanks, and stainless steel. It provides information on the most common generic coating systems used for new steel tanks and water storage tanks. It concludes with a discussion of quality watch-outs when selecting or using protective coatings in municipal water systems.

Commercial zinc plating is accomplished by a number of distinctively different systems: cyanide baths, alkaline noncyanide baths, and acid chloride baths. This article focuses on the composition, advantages, disadvantages, operating parameters, and applications of each of the baths. It provides information on the control of thicknesses of zinc specified for service in various indoor and outdoor atmospheres and on the similarities between cadmium and zinc plating.

Iron has been electroplated from a variety of electrolytes, whose bath parameters result in coatings that have widely divergent characteristics according to the specific characteristics desired in the finished product. This article provides an overview of the process description and processing equipment and discusses the properties, advantages, limitations, and principal applications of iron plating. It also describes the environmental, health, and safety considerations of iron plating.

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.

Chromium alloys yield alloy coatings with properties that range from completely satisfactory to marginally acceptable, depending on the end use. This article provides a detailed description of plating solutions and deposition conditions and rates of chromium-iron, chromium-nickel, and chromium-iron-nickel alloys.

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.

This article presents a detailed account of ion chromatography (IC). It begins by describing the principles of common separation modes in IC. This is followed by a section on the different modes of detection, namely suppressed conductivity detection, nonsuppressed conductivity detection, spectrophotometric detection, and electrochemical detection. Various separation modes in IC are then described. The article further provides information on various eluents species, analyte range, and sample preparation techniques in IC. It ends by providing information on the instrumentation and applications and future directions of IC.