Journal of Chemical Technology and Metallurgy, 48, 3, 2013 308 Journal of Chemical Technology and Metallurgy, 48, 3, 2013, 308-315 STATIONARY AND PULSE ELECTRODEPOSITION OF CoNi AND CoNiCu COATINGS K. Ignatova 1 , Y. Marcheva 2 1 University of Chemical Technology and Metallurgy 8 Kl. Ohridski, 1756 Sofa, Bulgaria 2 Technical University – Sofa, Sofa 1000, Bulgaria ABSTRACT The kinetics of stationary and pulse potentiostatic electrodeposition of Co, Ni and Cu as well as the possibility for their co-deposition in alloys CoNi and CoNiCu from slightly acidic citrate electrolyte was investigated. The morphologies and the elemental composition of coatings were studied using SEM and EDSA analysis respectively. It was established that at pulse deposition of CoNi the coatings were with smooth surface, crystalline structure with rounded crystals and average size about 200-300 nm at frequency 500 Hz. In the case of triple alloy CoNiCu deposition, with the increase of frequency up to 1 000 Hz a fner nanosized structure was formed, with the Ni content up to 27 %. The Co content in the triple alloy was not infuenced substantially by the pulse frequencies and was about 71-76 %, while copper content decreased from 8 % to less than 5 %. The X-Ray analysis indicated that copper, cobalt, and nickel crystallize in cubic lattice (fcc) in all studied alloy coatings. Besides the cubic phases of the three metals, the presence of cobalt-containing phase with hexagonal crystal lattice (h.p.c.) was ascertained. Keywords: alloy electrodeposition, pulse potential modes, voltammetry, morphology, elemental and phase com- position of coathings. Received 23 November 2012 Accepted 15 May 2013 INTRODUCTION In recent years an increasing interest exists towards electrodeposition of Co and CoNi-alloyed [1-7] and multi-layer coatings [6-8]. The particular interest to- wards nano-sized Co alloys is due to their increasing application in magnetosensor technologies and mag- netoelectronics where miniaturization of items is the underlying purpose [9-14]. Due to their high hardness, wear resistance, endurance and corrosion resistance, the cobalt alloys are widely used in medicine, nuclear- power systems, chemical- and oil industry [12, 15, 16]. The hardness of nano-sized coatings increases with the reciprocal of the square root of crystals grain size ac- cording to the Hall-Petch dependency [17]. The СоNi coatings are deposited mainly from sul- phate [18] and citrate [1,6,7,19] electrolytes. However, the literature does not provide detailed data about the kinetics and the deposition conditions of these alloys. The citrate electrolyte is used in recent years because of its ability to serve as a buffer, to form complexes, and to add coating luster, thus avoiding the need of introduction of special organic additives [7]. The diffculties in using this electrolyte come from its stability. It was found [21], that the stability of citrate electrolyte for deposition of CuNi coating can be controlled by modifying the pH. It decreases upon reaching рН levels bellow 4, which corresponds to complexes CuHCit, Cu 2 Cit 2 -2 and NiНCit. The stable electrolyte corresponds to рН = 5-6. The phase content of CoNi changes depending on the deposition conditions [2, 3, 25]. The alloys, depos- ited at more positive potentials contain ε-phase with hexagonal close-packed (hcp) lattice and α-phase with cubic lattice (fcс), the proportion between phases re- mains constant [25]. The CoNi alloys, deposited at more negative potentials contain pure cobalt and mixture of α- and ε-phases. Anomalous galvanostatic deposition in glucinate bath of CoNi [21] and potentiostatic deposition of CoNi and CoNiCu in citrate bath [25] were performed. It was established formation of CoNi solid solution with hexagonal close packed lattice [21] and solid solution of NiCoCu with face centered cubic lattice [25].