Electroplating metal deposition

Indium chemicals and electroplated metal deposits ate replacing mercury (qv) in the manufacture of alkaline batteries (qv). Indium, like mercury, functions to reduce outgassing within the battery and promotes the uniform corrosion of the anode and cathode while the battery is under electrical load. Indium inorganic chemicals also find use as catalysts in various chemical processes. 

Cathode Efficiency. Faraday s law relates the passage of current to the amount of a particular metal being deposited ie, 96,485 coulombs, equal to one Faraday, deposits one gram-equivalent weight of a metal at 100% efficiency. The cathode efficiency, an important factor in commercial electroplating, is the ratio of the actual amount of metal deposited to that theoretically calculated multipHed by 100%. 

Satisfactory service of an electroplated article is not achieved, however, unless adequate care is given to the choice of deposited metal, its thickness, the technique of application, and the design of the article. The choice of metal deposit is primarily determined by the basis metal, i.e. the metal from which the article is made, and the actual conditions to which the plated article will be subjected during service. In addition, however, attractive appearance and reasonable cost are also important considerations. 

Polarization in metal deposition is highly sensitive to solution composition. When present in the solution, a number of complexing agents and surfactants will strongly enhance it. In electroplating, it is very common that metals are deposited from solutions of their complex salts (e.g., cyanide complexes). In such solutions, the metal exists in the form of different complex anions, of the type with different... 

You have learned that electroplating is a process in which a metal is deposited, or plated, onto the cathode of an electrolytic cell. In this investigation, you will huild an electrolytic cell and electrolyze a copper(II) sulfate solution to plate copper onto the cathode. You will use Faraday s law to relate the mass of metal deposited to the quantity of electricity used. 

Electrolytic metal deposition ( electroplating ) is an empirical art widely in use to cover corrosion-sensitive surfaces with a thin protecting metal layer, e.g. of tin, nickel, zinc, etc. The complete plating process comprises several partial processes such as mass transport, charge transfer, adsorption of adatoms, surface diffusion of adatoms, and finally nucleation and crystal growth. 

Substrate Treatment. When the desired image is developed in the resist, the pattern created provides a template for substrate modification. The various chemical and physical modifications currently used can be classified into additive and subtractive treatments. Examples of additive treatments include the insertion of dopants (by either diffusion or ion implantation) to alter the semiconductor characteristics and metal deposition (followed by lift-off or electroplating) to complete a conduction network. In most cases, however, the substrate material is etched by a subtractive process. 

Figure 12.3. Schematic cross section showing microroughness of cathode and the attending diffusion layer with leveling agent accumulated at peaks (P). Metal deposition is inhibited at peaks but not at valleys (V). Filling the latter, results in smoother surfaces. (From Modern Electroplating, F. Lowenheim, ed., 1974 with permission from Wiley.)...

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