The fundamental objective of quenching is to preserve, as nearly as possible, a metastable solid solution formed at the solution heat treating temperature, by rapidly cooling to some lower temperature, usually near room temperature. This article provides an overview of the factors used to determine a suitable cooling rate and the appropriate quenching process to develop a suitable cooling rate. It discusses the three distinct stages of quenching: vapor stage, boiling stage, and convection stage. The article reviews the factors that affect the rate of cooling in production operations. It discusses the quenchants that are used in quenching aluminum alloys, namely, hot or cold water and polyalkylene glycol. The article also describes the racking practices for controlling distortion and the level of residual stresses induced during the quench.

Quenching refers to the rapid cooling of metal from the solution treating temperature, typically between 465 and 565 deg C (870 and 1050 deg F) for aluminum alloys. This article provides an overview on the appropriate quenching process and factors used to determine suitable cooling rate. It describes the quench sensitivity and severity of alloys, quench mechanisms and the different types of quenchants used in immersion, spray, and fog quenching. The article provides a detailed description of the quench-factor analysis that mainly includes residual stress and distortion, which can be controlled by proper racking. It concludes with information on agitation and the quench tank system used in the quenching of aluminum alloys.

This article describes the criteria for selecting a corrosion-monitoring method used in industrial plants. It provides a detailed discussion on the design, advantages, and disadvantages of plant corrosion-testing program. The basic types of racks used to support and insulate the coupons are also discussed. The analysis of electrical-resistance probes, sentry holes, side-stream loop, electrochemical noise, hydrogen-probe, and process streams are used to monitor and estimate corrosion rates. The corrosion rates can also be estimated by ultrasonic thickness measurements, polarization-resistance measurements, corrosion potential measurements, and alternating current impedance measurements. Corrosion monitoring strategies, such as locations, data analysis, redundancy, and other issues, are discussed. The article concludes with information on the interpretation and reporting of corrosion testing.

This article discusses the different classes of gears, namely, spur, helical, herringbone, crossed-axes helical, worm, internal, rack, bevel, or face-type. It describes the methods used to cut the teeth of gears other than bevel gears: milling, broaching, shear cutting, hobbing, shaping, and rack cutting. The article also reviews the methods that are used to cut the teeth of bevel gears, such as face mill cutting, face hob cutting, formate cutting, helix form cutting, the Cyclex method, and template machining. The machining methods best suited to specific conditions are discussed. The article presents the factors influencing the choice of cutting speed and cutting fluids. It outlines two basic methods for the grinding of gear teeth: form grinding and generation grinding. The article concludes with information on the gear inspection techniques used to determine whether the resulting product meets design specifications and requirements.

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.

Simulated service testing is the most reliable predictor of corrosion behavior that is important for specific objectives. These include materials selection, predicting the probable service life of a product or structure, evaluating new commercial alloys and processes, and calibrating laboratory corrosion tests in short of in-plant tests and actual service experience. This article provides a detailed discussion on the types of atmospheres used in simulated service testing. It describes the specifics of atmospheric-corrosion test that include equipment, test arrangement, and test specimen; factors affecting atmospheric corrosion; and evaluation of exposed atmospheric-corrosion panels. The article concludes with a discussion on the empirical model used for analyzing the atmospheric-corrosion measurements for estimating the service life of the part being evaluated.

The process of coating plastics with metals for functional purposes is called metallizing of plastics. This article discusses the metallizing of plastics, provides information on its history, and gives a short note on applications and adhesion properties of metallic coatings. It also discusses the selection of plastics for plating. This article also describes metallizing techniques, including plating (electrolytic or electroplating), vacuum metallizing and thermal spraying, and environmental considerations. The article discusses the quality assurance procedures for metallized plastic parts which include tests that assess the quality of the finish, coating thickness, adhesion, and corrosion resistance, and gives a short note on service performance, which includes service condition classifications.

This article presents a general overview of outdoor weather aging factors, their effects on the performance of polymeric materials, and the accelerated test methods that can be used to investigate those effects. These test methods are used to characterize material performance when subjected to specific, often controlled, and well-defined factors. The article also presents an overview of weathering instrument types that simulate outdoor stress factors.

The chemicals that have been used in traditional vapor degreasing have serious health and environmental hazards that have prompted the search for modified and alternative techniques. This article provides a detailed discussion on the regulatory mandates that affect the use of industrial degreasing methods. It describes the aqueous degreasing technique, which forms an attractive alternative to the traditional vapor degreasing process. The article includes information on the materials and equipment used in the process, and discusses the advantages and disadvantages of hot and dip tank systems of aqueous degreasing. It explains how to convert an existing vapor degreaser to an aqueous cleaning system.

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.

Etching aluminum can be a pretreatment step for anodizing, chemical conversion coating, metal-to-rubber bonding, and a host of other processes. Chemical etching, using either alkaline or acid solutions, produces a matte finish on aluminum products. This article describes the alkaline etching and acid etching of aluminum. Alkaline etching reduces or eliminates surface scratches, nicks, extrusion die lines, and other imperfections. Acid etching can be done without heavy smut problems, particularly on aluminum die castings. Hydrochloric, hydrofluoric, nitric, phosphoric, chromic, and sulfuric acids are used in acid etching. The article presents a flow chart of the operations used in acid etching.

Anodizing refers to conversion coating of the surface of aluminum and its alloys to porous aluminum oxide. This article provides the reasons for performing anodizing and discusses the three principal types of anodizing processes, namely, chromic acid process, sulfuric acid process, and hard anodic process. It describes the limitations imposed by variables, such as alloy composition, surface finish, prior processing, temper or heat treatment, and the use of inserts, on the anodizing processes. The article explains the causes and means adopted for correcting several specific problems in anodizing aluminum. It also discusses the process control techniques and equipment used for anodizing. The article reviews the sealing processes for anodic coatings and the method for coloring the coatings. It concludes with a discussion on the effects of anodic coatings on the surface and mechanical properties of aluminum and its alloys.

Corrosion monitoring is important in the operation of modern industrial plants and in the use and maintenance of expensive assets such as bridges and aircrafts, because the damage caused by corrosion and the rate of the deterioration can be huge and the risks devastating. This article discusses the system considerations and installation techniques of different types of direct and indirect techniques in electrochemically based on-line corrosion monitoring process. It describes the importance of probe location and on-line corrosion monitoring techniques with examples.

This article focuses on the mineral and organic acid cleaning of iron and steel. It begins with a discussion on the application methods, process selection criteria, solution composition, equipment used, and control of process variables in mineral acid cleaning. The article then describes the advantages and disadvantages of organic acid cleaning. Applications, including boiler cleaning, stainless steel cleaning, and removal of iron- and copper-bearing deposits, are discussed. The article concludes with an overview of acid cleaning of nonferrous alloys.

Anodizing produces a uniform, continuous, highly ordered network of individual cells comprising a layer whose thickness and cell dimensions, and ultimately engineering properties, depend on the electrochemical parameters of the anodizing process. This article discusses the nucleation and growth of anodic aluminum oxide and the important characteristics of the finished porous anodic aluminum oxide. In industry, anodic oxides and the anodizing processes have been categorized into types that exhibit specific properties to suit specific applications. The article reviews the two most basic types of oxides, namely, barrier-layer anodic oxides and porous anodic oxides. It concludes with a description of postanodizing processes, such as dyeing and sealing.

This article suggests procedures to increase the availability and function of patterns and tooling. It discusses the common expected failure mechanisms, such as erosion and fatigue, for dies and patterns. A successful maintenance program requires good record keeping for each tool. The article lists information required for the maintenance tooling record and preventive maintenance (PM) items from the North American Die Casting Association's publication E501. It concludes with information on objectives for proper storage of tools and patterns. The objectives are preventing tool degradation, safe workplace, easy location, proximity, and cataloging and tracking.

This article presents general design principles for different types of surface-finishing processes, such as cleaning, organic coatings, and inorganic coatings applied by a variety of techniques. It discusses the factors that influence the selection of surface-finishing processes. These include fabrication processes, size, weight, functional requirements, and design features. The article discusses the design as an integral part of manufacturing. It contains tables that summarize the design limitations for selected surface-preparation, organic finishing, and inorganic finishing processes.

This article discusses the process considerations and deposit properties of nickel plating. It describes the Watts solution and the anode materials used. The article focuses on the nickel plating processes used for decorative, engineering, and electroforming purposes. It provides information on the quality control of nickel plating. It concludes with a review of the environmental, health, and safety considerations associated with nickel plating.

This article provides information on the various stages of quenching, sources of distortion, and factors that affect the creation of thermal gradients. It reviews the various determinations of heat-transfer coefficients by the thermal conductivity and diffusivity method, analytical and empirical methods, application of cooling curves, computational fluid dynamics, and the inverse conduction calculation and measurement of parts. Suitable examples are also provided.

This article discusses the various factors that affect the corrosion performance of electroplated coatings. It describes the effects of environment and the deposition process on substrate coatings. The article provides a discussion on the electrochemical techniques capable of predicting the corrosion performance of a plated part. It reviews the designs of coating systems for optimal protection of the substrate. The article also discusses controlled weathering tests and accelerated tests used to predict and determine the relative durability of the coating.