Applications electroless plating

Nickel containing scales exhibit higher conductivity because of the presence of trivalent nickel ions, which introduce vacancies in the lattice of the scale. Therefore, nickel-based coating can lead to superior conductivity and good protection provided that it is alloyed properly with corrosion resistant elements. Cobalt has a lower solubility in molten carbonate and electroless Co has been successfully used for a variety of corrosion-resistant applications. Electroless plating of Ni-Co gives rise to deposition of uniform layers of nanostructured material, which would result in better protection of the substrate. 

J. Hajdu and G. Mallory, Electroless Plating. Fundamental and Applications, American Plating and Surface Finishing Society, Orlando, Fla., 1990. 

G. 0. Mallory, in Electroless Plating Fundamentals and Applications, Ed. by G. 0. Mallory and J. B. Hajdu, American Electroplaters and Surface Einishers Society, Orlando, EL, 1990, p. 1. 

Fig. 10. Time dependence of corrosion rate of Co8P and Co films, electrolessly plated and sputter-deposited onto NiP substrates, in a droplet of DI water. The results were obtained by a repeated application of the polarization resistance technique with the potential scanned at 1 mV/sec in a potential range 15 mV above and below the corrosion potential [125]. (Reprinted by permission of The Electrochemical Society). 

Architectural Glass. The other important commercial glass-plating application is for production of architectural reflective glasses. Translucent metal films are used for decoration and for reduction of environmental heat gain. Electroless plating is used by one producer for this type of product (48). 

Other Baths. Other forms of zinc plating are also in use. Immersion zinc deposits are used as a preparatory step in electroless plating or electroplating of aluminum (146), magnesium (147), and beryllium (148) alloys. Formulations vary with the application typical baths are listed in the references cited. 

Electrolessly plated cobalt-phosphorus thin films are usually characterized by low to medium coercivity values [300-900 Oe (oersteds)]. For some applications, it would be desirable to have films with coercivities greater than 900 Oe. Table 16.1 shows that films with minimum preferred orientation exhibit maximum coercivity values. The ratio of the intensity of the (002) and (101) diffraction rings changes with hypophosphite concentration of the plating solution with zero preferred orientation obtained at solution hypophophite concentrations of 5-6 w/o (weight %). 

Electroless plating — An autocatalytic process of metal deposition on a substrate by reduction of metal ions from solution without using an external source of electrons. It is promoted by specific reductants, namely formaldehyde, sodium hypophosphide, sodium boro-hydride, dialkylamine borane, and hydrazine. Electroless deposition has been used to produce different metal (e.g., nickel, cobalt, copper, gold, platinum, palladium, silver) and alloy coatings. It can be applied to any type of substrate including non-conductors. Some substrates are intrinsic catalytic for the electroless deposition other can be catalyzed usually by sensibilization followed by Pd nucleation also, in some non-catalytic metallic substrates the electroless process can be induced by an initial application of an appropriate potential pulse. In practical terms, the evaluation of the catalytic activity of a substrate for the electroless deposition of a given metal is... 

The technique of electroless plating is in principle attractive for industrial applications because of its unique advantages over conventional electrolytic plating. These advantages include (1) the ability to deposit a metal on catalyzed nonconductive substrates, (2) the ability to plate substrates with complex shapes at a uniform metal thickness, and (3) the ability to selectively deposit a metal on catalyzed areas of the substrate surface only. Because of these advantages, industry has found a number... 

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