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Portugaliae Electrochimica Acta

versão impressa ISSN 0872-1904

Port. Electrochim. Acta v.24 n.4 Coimbra  2006


Impedance measurements for electroless nickel plating process

 S. Karthikeyan,a),* K.N. Srinivasan,b) T. Vasudevan,c) S. Johnb)

 a) Department of Chemistry, National Engineering College, Kovilpatti-628503, India

b) Central Electrochemical Research Institute, Karaikudi-630 006, India

c) Department of Industrial Chemistry, Alagappa University, Karaikudi-630 003, India



Received 22 November 2004; accepted November 2006



Electroless nickel (EN) process is the controlled auto catalytic reduction of nickel ions using suitable reducing agent such as sodium hypophosphite on certain catalytic surfaces, which results in the production of sound, coherent coatings for a number of applications. Frequently the rate of deposition of EN with hypophosphite as reducing agent is below 20 microns per hour. Hence the deposition of the electroless nickel with hypophosphite solution in the presence of small concentration of thiourea and its derivatives as accelerators is investigated. The mechanism of accelerated deposition is studied by impedance measurements. The performance of various additives during the plating process is being evaluated by increased Constant Phase Element (CPE) and decreased charge transfer resistance values. A model is proposed for the adsorptive behavior of additives.

Keywords electroless nickel, impedance studies, accelerators, thiourea and its derivatives.


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