Cadmium electroplating processes

ASTM F326, Std Test Method for Electronic Hydrogen Embrittlement Test for Cadmium Electroplating Processes, American Society for Testing and Materials, Philadelphia, Pa. 

Standard Test Method for Evaluating the Influence of Thermal Insulations on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel Standard Test Method for Electronic Measurement for Hydrogen Embrittlement fi-om Cadmium-Electroplating Processes... 

The U S. EPA is funding research at Ionedge Corporation, Fort Collins, Colorado, to develop a process for zinc-graphite and zinc-cadmium alloy dry plating as environmentally safer alternatives to cadmium electroplating in cyanide baths. Successful development of these technique could lead to a method which would potentially eliminate the environmental and occupational hazards associated with cadmium electroplating. 

The aluminizing process is a clean operation and the final products (Fig. 23), i. e., aluminum-coated metals, pose no environmental threat. We know today that aluminum can to a large extent replace cadmium as a corrosion-protective coating for work pieces [176]. Since cadmium is applied extensively in automobiles, aviation, on- and offshore industries, aluminum coating, i.e. both the aluminum electroplating process and the resulting coated pieces play an important role in environmental protection. The properties of the electrolytically produced aluminum layers on work pieces for aviation and space technology have been tested [183]. 

However, there are also drawbacks with the electroplating process. In practice, electroplating is not as simple as the description above suggests. It is difficult to get metal to deposit in depressions, so the metal layer often is not uniform. Sometimes, deposits are loose and powdery. Additives are used and conditions such as temperature and pH are carefully controlled to overcome these problems. Over time, impurities build up in the solutions used for electroplating. Eventually, the spent solutions must be discarded. They can contain high concentrations of such toxic metals as cadmium or chromium and require careful disposal to protect the environment. 

Cadmium is widely used in pigments, electroplating processes, and alkaline batteries. It is also a component of cigarette smoke. It has long been known to cause renal cancer in humans, I35l and is also associated with cancer of the lung, pancreas, breast, prostate, and bladder. I36l... 

This method uses a metal-shelled vacuum probe as an ion gage. A section of the probe shell is cadmium-plated at the lowest current density encountered during the electroplating process. During the subsequent baking, the probe ion current, which is proportional to hydrogen pressure, is recorded tis a function of time. The slope of this curve has an empirical relationship to failure data, as discussed in ASTM STP 543 [261... 

Other sources of potential environmental contamination by cadmium are cigarette smoke, electroplating processes, paint pigments, the cadmium-nickel type of automobile storage battery, certain phosphate fertilizers, and some of the older types of galvanized water tanks. 

Electroplated Metals and Alloys. The metals electroplated on a commercial scale from specially formulated aqueous solutions iaclude cadmium, chromium, cobalt, copper, gold, iadium, iron, lead, nickel, platinum-group metals, silver, tin, and ziac. Although it is possible to electroplate some metals, such as aluminum, from nonaqueous solutions as well as some from molten salt baths, these processes appear to have achieved Httie commercial significance. 

Concentrated, aqueous solutions of ZnCla dissolve starch, cellulose (and therefore cannot be filtered through paper ), and silk. Commercially ZnCla is one of the important compounds of zinc. It has applications in textile processing and, because when fused it readily dissolves other oxides, it is used in a number of metallurgical fluxes as well as in the manufacture of magnesia cements in dental fillings. Cadmium halides are used in the preparation of electroplating baths and in the production of pigments. 

Electroplating. Typical wastes produced include spent process solutions containing copper, nickel, chromium, brass, bronze, zinc, tin, lead, cadmium, iron, aluminum, and compounds formed from these metals. 

Uses. The metal is used in electroplating, in solder for aluminum, as a constituent of easily fusible alloys, as a deoxidizer in nickel plating, in process engraving, in cadmium-nickel batteries, and in reactor control rods. Cadmium compounds are employed as TV phosphors, as pigments in glazes and enamels, in dyeing and printing, and in semiconductors and rectifiers. 

Composts can be made from most biodegradable materials, and could derive from many unusual sources. If it originates from municipal solid waste, however, care should be taken that no toxic and non-degradable materials remain after the supplier s separation processes. Small pieces of brick and concrete, glass and plastic (inerts), lead residues from old car batteries and cadmium from electroplated items are possible. A useful work on specifications and recommended chemical analyses of composts is the book by Bertoldi et al., 1987. 

Cadmium iodide is used in lithography, process engraving, photography, electroplating, and in the manufacture of phosphors. 

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