Cadmium plating applications

Health and Safety Cadmium metal and its compounds are toxic and are injurious to health, and for this reason, cadmium is being replaced by other forms of coating wherever possible. For a number of important applications, however, no suitable alternatives have yet been identified. Where cadmium plating continues to be used, it is essential to comply with the regulations covering the use of cadmium. 

Cadmium Cadmium plating is used to increase the corrosion resistance of steel fasteners and electrical connectors. However, the Cd plate is itself subject to oxidation and tarnishing in humid and tropical environments to such an extent that electrical and mechanical functionality may be adversely affected. CCCs may are applied to Cd to resist oxidation, or to increase paintability [81]. Cd plating can be successfully conversion coated using chemistries applicable to other metals. 

Cadmium and its compounds in electrical contacts and cadmium plating except for applications banned under Directive 91-338-EEC... 

Cadmium and zinc electroplating provides galvanic corrosion protection when coated on steel. Deposit thickness can vary between 5 and 25 p,m (0.2 and 1 mil), and typical applications for both coatings are found in Table 10. Cadmium is preferred for the protection of steel in marine environments, whereas zinc is preferred in industrial environments. Cadmium is also preferred for fastening hardware and connectors because its coefficient of friction is less than zinc. Cadmium is toxic and should not be used in parts that will have contact with food. Precautions for minimizing hydrogen embrittlement should be taken because cadmium plating is more susceptible to such embrittlement than any other plated metal. 

Lower cost and lower weight cylindrical cells have been made using plastic bound or pasted actwe material pressed into a metal screen. Tliese cells suffer slightly in utilization at high rates compared to a sintered-plate cylindrical cell, but they may be adequate for most applications. Tlie effect of temperature and discharge rate on the capacity of sealed nickel-cadmium cells is illustrated in Figure 8 and Table 3. 

Aluminium is widely applied for decorative and protective requirements, while cadmium , zinc and titanium have been applied to ferrous materials chiefly for their protective value. The method finds particular application in the plating of high-tensile steels used in aviation and rocketry, car fittings and lamp reflectors, and gramophone record master discs, as well as in the preparation of specimens for electron microscopy and in rendering insulated surfaces electrically conducting, e.g. metallising of capacitors and resistors. 

Tin coatings are widely used in the electrical industry because of their good contact properties and in the food industry because of low toxicity. In addition to pure tin coatings a number of alloy coatings have been developed for special applications, e.g. tin-lead (terne plate), tin-zinc, tin-cadmium, tin-bronze and tin-nickel. Reference should be made to Section 13.5 and to the publication by Britton for data on the corrosion of tin and its alloys. 

Although one of the most common storage batteries is called the nickel/cadmium system ( NiCad ), correctly written (-)Cd/KOH/NiO(OH)(+), cadmium is not usually applied as a metal to form a battery anode. The same can be said with regard to the silver/cadmium [(-) Cd / KOH / AgO (+)] and the MerCad battery [(-)Cd/KOH/HgO(+)]. The metallic negative in these cases may be formed starting with cadmium hydroxide, incorporated in the pore system of a sintered nickel plate or pressed upon a nickel-plated steel current collector (pocket plates), which is subsequently converted to cadmium metal by electrochemical reduction inside the cell (type AB2C2). This operation is done by the customers when they start the application of these (storage)... 

Protecting a surface from corrosion by coating can be accomplished by a number of well-established processes which include paints, metal plating (with zinc or cadmium), diffusion, thermal spraying, and, more recently, vapor deposition processes. Of these physical vapor deposition (PVD) is used extensively in corrosion protection. Typical applications are ... 

Subcategory A encompasses the manufacture of all batteries in which cadmium is the reactive anode material. Cadmium anode batteries currently manufactured are based on nickel-cadmium, silver-cadmium, and mercury-cadmium couples (Table 32.1). The manufacture of cadmium anode batteries uses various raw materials, which comprises cadmium or cadmium salts (mainly nitrates and oxides) to produce cell cathodes nickel powder and either nickel or nickel-plated steel screen to make the electrode support structures nylon and polypropylene, for use in manufacturing the cell separators and either sodium or potassium hydroxide, for use as process chemicals and as the cell electrolyte. Cobalt salts may be added to some electrodes. Batteries of this subcategory are predominantly rechargeable and find application in calculators, cell phones, laptops, and other portable electronic devices, in addition to a variety of industrial applications.1-4 A typical example is the nickel-cadmium battery described below. 

The above metals are used in many industrial processes. Cadmium, for instance, is plated onto fabricated metal parts to provide corrosion resistance, lubricity and other desirable properties it is used in rechargeable batteries, television and fluorescent light phosphors, inorganic coloring agents for paint, plastic and printing ink, and as a catalyst. Applications of the metals listed above are detailed in Table 2-1, categorized by Standard Industrial Classification (SIC) codes. These industries are discussed further in Section 4.0. 

The combination of different fluorescent metal indicators with inert luminescent reference beads consisting of poly(acrylonitrile) containing Ru(dpp)3 leads to a sensor array in a microwell plate format, suited for ratiomet-ric time-resolved imaging [95]. The data can be acquired with the help of the f-DLR method (for details see Sect. 2.3). A cross-reactive sensor array was arranged for the determination of mixtures of calcium(II), copper(II), nickel(II), cadmium(II), and zinc(II) ions by nine different commercially available fluorescent indicators (Table 3). For a successful application, it is mandatory that all luminophores can be excited at the same wavelength range between 400 and 500 nm, and that the excitation and emission spectra of all indicators overlap with those of the reference dye encapsulated in the nanobeads. 

Analyses for "copper, cadmium, and lead were carried out continually by DPASV. Zinc determinations were excluded to permit use of a lower electrolysis potential. The samples were analyzed at pH 4.9 by sparging with carbon dioxide. An 8-min. electrolysis at —1.0 V vs. silver/ silver chloride and a 25-mV pulse were used during the Seattle-Saanich portion of the trip (Leg 1) while a 10-min. electrolysis and a 50-mV pulse were used from Saanich to Seattle (Leg 2). Application of the DPASV technique resulted in greater sensitivity and thus shorter plating times for the low levels encountered. It also afforded better resolution for "copper than linear-sweep ASV. It should be pointed out, however, that DPASV does not result in shorter analyses times because the stripping portion of the analysis is very slow. Nevertheless, it is worthwhile to limit the time of electrolysis because this also reduces the concentrations of interfering metals accumulated in the mercury fllm. Under the... 

Nickel oxide electrodes constitute the positive plates of several storage systems (among which nickel-zinc, nickel cadmium, nickel metal-hydride, sodium-nickel chloride) [16]. In recent years, the high-specific energy and specific power of Ni-Zn systems has increased the interest in their use for electric vehicles with respect to the past years, when their application was essentially limited by a short cycle life. 

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