Electrodeposition of Co-rich Cu-Co Alloys from Sodium Tartrate Baths Using Direct (DC) and Single Pulsed Current (SPC)

Abstract

Cu-Co alloys were electrodeposited on steel substrates from alkaline sodium tartrate electrolyte using direct and single pulsed current (DC and SPC, respectively). The electrodeposition bath was composed by 0.02 mol L−1 of CuSO4.5H2O, 0.10 mol L−1 of CoSO4.7H2O and 0.50 mol L−1 of Na2C4H4O6.4H2O. Using both kind of deposition processes, it was verified that the applied current density (j) affected the cathodic current efficiency (Ef), the copper and cobalt contents in the coatings (wt. % Cu and wt. % Co, respectively), the morphology and the anticorrosive performance of the coatings (based on the transfer charge resistance, (Rct) values). Comparing the results obtained for DC and SPC coatings, those produced by single pulsed current improved the Ef values and decreased the grain sizes. Concerning the conditions used in this work, the coating produced under the conditions of Experiment 4’, using jm = 40 A m-2 and SPC mode, presented 15.9 wt. % Co, the most compact morphology, the smallest grain size and the highest Rct value after 24 h of exposure in the saline medium.

Keywords

• Electrodeposition
• Cu-Co alloys
• sodium tartrate baths
• anticorrosive coatings