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Optimization of Mechanical Properties of Nickel-Cobalt Coatings from Sulphamate Baths

Karakaya, Esra
Başkan, Mertcan
Erdoğan, Metehan
Karakaya, İshak
Nickel-cobalt alloys are important coating materials due to their magnetic properties [1-2], wear resistance [3-4] and electrocatalytic properties [5]. Their deposition from sulfamate electrolytes has many advantages including low internal stress, homogenous deposition at high current densities, high current efficiencies and higher hardness as compared to the conventional Watts electrolyte [6]. A statistical experimental design was used to study the effects of boric acid and nickel chloride concentrations, bath temperature and applied current density on nickel coatings in sulphamate baths. After the optimization of the electrolyte composition, effects of pH and Co additions to the electrolyte were investigated. The coating thickness and its distribution were measured by XRF techniques. Microhardness, surface morphology and internal stress of coatings were also determined. It was found that Co addition to the electrolyte and operation at higher pH yielded deposits of higher Co content and enhanced hardness up to a certain point.