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 CuSO 4 .5H 2 O, 0.10 mol L −1 of CoSO 4 .7H 2 O and 0.50 mol L −1 of Na 2 C 4 H 4 O 6 .4H 2 O. Using both kind of deposition processes, it was verified that the applied current density (j) affected the cathodic current efficiency (E f ), 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, (R ct ) values). Comparing the results obtained for DC and SPC coatings, those produced by single pulsed current improved the E f values and decreased the grain sizes. Concerning the conditions used in this work, the coating produced under the conditions of Experiment 4', using j m = 40 A m -2 and SPC mode, presented 15.9 wt. % Co, the most compact morphology, the smallest grain size and the highest R ct value after 24 h of exposure in the saline medium.

Production of low-Sn Cu-Sn Alloy Coatings onto Steel Substrate Using Sodium Citrate Bath – Part 1: the Effect of Current Mode (DC or SPC) and Applied Current on the Chemical, Morphological, and Anticorrosive Properties of the Coatings

“…Thus, it would be possible to verify differences in the chemical composition of the coatings produced by DC and SPC deposition processes and the effects observed in this property due to the current variation. The same conditions used here have already been applied for Cu-Co alloy coatings produced by the group, with satisfactory results 34 . The deposition conditions for producing the DC and SPC coatings are shown in Table 2.…”

“…On the other hand, as in the SPC electrodeposition the current is periodically switched off, this layer can be partially discharged, allowing the ions to reach the electrode surface more easily. Thus, in the SPC process, the concentration of the metallic ions close to the cathode, which decreases after a high deposition rate during the current application time (t on ), can be recovered by ion migration, diffusion, and convection during the current-off time (t off ) 34,46 . This effect is reflected by E f maintenance of around 100% for most of the SPC coatings, as verified in Table 3.…”

Electrodeposición de cobalto sobre oro a partir de un baño electrolítico a base de bitartrato.

“…La electrodeposición de cobalto sobre sustratos de oro se ha realizado a partir de soluciones de sulfato, (Szmaja, et al, 2012, Krause, et al, 2007, Joo, et al, 2007, y Krause, et al,2004, acetato (Beaurepaire, et al, 1997) y cloruro (Joo, et al, 2007, Mendoza-Huizar et al, 2002, Mendoza-Huizar et al, 2003, Mendoza-Huizar et al, 2005. Por otro lado, se han reportado muy pocos estudios en donde se analiza la influencia del ion en el proceso de electrodeposición de cobalto (De Souza et al, 2019) dichos estudios se ha encontrado que el proceso de reducción del cobalto (II) se favorece cuando la solución contiene al ion tartrato. Los iones bitartrato, provenientes del ácido tartárico (al igual que los iones tartrato) no se han utilizado como electrolito soporte para electro depositar el cobalto, esto probablemente se debe a su menor conductividad en comparación con la exhibe el ion tartrato.…”