Search Results for chromic anhydride

Most decorative chromium coatings have been applied using hexavalent and trivalent plating processes that are based on chromic anhydride. This article provides a discussion on chromium electrodeposits and their use as microdiscontinuous coating for corrosion protection. It focuses on the operating conditions of various chromium plating parameters: bath composition, temperature, voltage, anode materials, and current density. These parameters need to be considered for obtaining high quality decorative chromium coatings. An overview of plating problems encountered in chromium plating and their corrections is also provided.

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 describes the safety precautions required for using laboratory equipment. It reviews the various personal protective equipment specified on the Material Safety Data Sheets (MSDS) for laboratory chemicals and products. The article provides information on the storage and handling of etchants, solvents, acids, bases, and other chemicals. It describes the safety precautions and procedures for handling concentrated and dilute hydrofluoric acid. The article concludes with a discussion on the precautions to be followed in the event of spills and cleanup.

Mixtures of acids or acids and salts are of great importance to the chemical process industry (CPI) for use in digestion of solids, as a promoter in reactions, as a scale remover, and as a complexant. This article emphasizes the assessment of the performance of Ni-Fe-Cr-Mo alloys in mixed acids and salts in an objective manner. It tabulates the nominal compositions of pertinent Ni-Fe-Cr-Mo corrosion-resistant alloys. The article describes the acid and acid-plus-salt mixtures classified into the following general categories: nonoxidizing acid mixtures (H 2 SO 4 +H 3 PO 4 ), nonoxidizing acids with halides (H 2 SO 4 +HCl), oxidizing acid mixtures without halides (H 2 SO 4 +HNO 3 ), and oxidizing acid mixtures with halides (HNO 3 +HF). It also illustrates the effect of alloying elements on the corrosion rate in the nonoxidizing mixtures and oxidizing acid mixtures.

Metallographic preparation of a material involves the elimination of artifacts or scratches from fine polishing and may be achieved by methods such as attack polishing, vibratory polishing, chemical polishing, electrolytic polishing, and electromechanical polishing. This article discusses the mechanism, operating procedure, advantages, and limitations of chemical and electrolytic polishing of samples for metallographic preparation. It provides information on the specimen preparation, apparatus used, and safety precautions to be followed during the polishing process. The various groups of electrolytes used in electropolishing of several metals and alloys are reviewed. The article concludes with a discussion on local electropolishing.

This article describes the methods and equipments involved in the preparation of specimens for examination by light optical microscopy, scanning electron microscopy, electron microprobe analysis for microindentation hardness testing, and for quantification of microstructural parameters, either manually or by the use of image analyzers. Preparation of metallographic specimens generally requires five major operations: sectioning, mounting, grinding, chemical polishing, and etching. The article provides information on the principles of technique selection in mechanical polishing, and describes the procedures, advantages, and disadvantages of electrolytic and chemical polishing. It also provides a detailed account of procedures, precautions, and composition for preparation and handling of etchants.

Metallographic contrasting methods include various electrochemical, optical, and physical etching techniques, which in turn are enhanced by the formation of a thin transparent film on the specimen surface. This article primarily discusses etching in conjunction with light microscopy and describes several methods for film formation, namely, heat tinting, color etching, anodizing, potentiostatic etching, vapor deposition, and film deposition by sputtering. It provides information on the general procedures and precautions for etchants and reagents used in metallographic microetching, macroetching, electropolishing, chemical polishing, and other similar operations.

This article describes selected U.S. environmental statutes and regulations that are pertinent to material surface finishers. It provides information on the applicability, requirements, and permitting conditions of the Clean Air Act, the Resources Conservation and Recovery Act, the Superfund Amendments and Reauthorization Act, and the Clean Water Act.

This article describes the metallographic technique for nonferrous metals and special-purpose alloys. These include aluminum alloys, copper and copper alloys, lead and lead alloys, magnesium alloys, nickel and nickel alloys, magnetic alloys, tin and tin alloys, titanium and titanium alloys, refractory metals and alloys, zinc and zinc alloys, and wrought heat-resisting alloys. The preparation of specimens for metallographic technique includes operations such as sectioning, mounting, grinding, polishing, and etching of nonferrous metals and alloys. The article contains tables that list the etchants for macroscopic examination and microscopic examination of nonferrous metals and special-purpose alloys.

This article is a compilation of definitions of terms related to metallography and microstructures.

Adhesive bonding is used to assemble composite components into larger structures. Finished components that are damaged during assembly or service are often repaired with adhesive-bonding techniques. This article summarizes criteria for adhesive selection and illustrates typical secondary adhesively bonded joint configurations. It discusses the highly loaded joint considerations of adhesives. The article describes the epoxy adhesives commonly used for the bonding or repair of composite structures. It discusses the surface preparation of composites and metals, and honeycomb processing, including perimeter trimming, mechanical forming, heat forming, core splicing, contouring, and cleaning. The article presents basic steps involved in the adhesive-bonding process and concludes with a discussion on adhesive applications and tooling.

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 is a comprehensive collection of tables listing: dangerous reactions of chemicals and designations of etchants; chemical-polishing solutions for irons and steels and nonferrous materials; attack-polishing solutions, macrostructure etchants for iron and steel; and major microstructure etchants for common phases and constituents in ferrous materials.

The high-temperature corrosion processes that are most frequently responsible for the degradation of furnace accessories are oxidation, carburization, decarburization, sulfidation, molten-salt corrosion, and molten-metal corrosion. This article discusses each corrosion process, along with the corrosion behavior of important engineering alloys. It describes the corrosion of plating, anodizing, and parts of pickling equipment such as tanks, wirings and bus bars, racks, anode splines, pumps, and heaters.

This article provides an overview of curing techniques, adhesive chemistries, surface preparation, adhesive selection, and medical applications of adhesives. The curing techniques are classified into moisture, irradiation, heat, and anaerobic. The article highlights the common types of curable adhesives used for medical device assemblies, including acrylics, cyanoacrylates, epoxies, urethanes, and silicones. Other forms of adhesives, such as hot melts, bioadhesives, and pressure-sensitive adhesives, are also discussed. The typical characteristics and applications of biocompatible medical device adhesives are listed in a table. The article concludes with a section on the selection of materials for medical adhesives.

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.

This article discusses the properties, primary and secondary production, product forms and applications of various grades of lead and lead-base alloys with the aid of several tables and illustrations. It lists the Unified Numbering System (UNS) designations for various pure lead grades and lead-base alloys grouped according to nominal chemical composition. The properties of lead that make it useful in a wide variety of applications are also discussed. The largest use of lead is in lead-acid storage batteries. Other applications include ammunition, cable sheathing, cast products such as type metals, terneplate, foils, and building construction materials. Lead is also used as an alloying element in steel and in copper alloys to improve machinability. The article concludes with information on the principles of lead corrosion, corrosion resistance of lead in water, atmospheres, underground ducts, soil and chemicals.

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.

Titanium alloys are often used in highly corrosive environments because they are better suited than most other materials. The excellent corrosion resistance is the result of naturally occurring surface oxide films that are stable, uniform, and adherent. This article offers explanations and insights on the most common forms of corrosion observed with titanium alloys, including general corrosion, crevice corrosion, anodic pitting, hydrogen damage, stress-corrosion cracking, galvanic corrosion, corrosion fatigue, and erosion-corrosion. It also provides practical strategies for expanding the useful application range for titanium and includes a comprehensive overview of available corrosion data.