Electrodeposition of Co–Rh alloys from aqueous acidic chloride electrolytes

• Published in: Surface & coatings technology Vol. 258; pp. 72 - 77
• Main Authors: Mech, K., Żabiński, P., Kowalik, R., Wojnicki, M.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15-11-2014; Elsevier
• Subjects: Alloys; Applied sciences; Chlorides; Cobalt base alloys; Co–Rh alloys; Cross-disciplinary physics: materials science; rheology; Electrode potentials; Electrodeposition; Electrodes; Electrolytes; Exact sciences and technology; Materials science; Metallic coatings; Metals. Metallurgy; Morphology; Physics; Production techniques; Silver; Surface treatment; Surface treatments; Transition group metals; Voltammetry; Electrodeposition; Voltammetry; Co–Rh alloys; Transition group metals; Metal coating; Chlorides; Electrolytes; Surface treatments; Co-Rh alloys; Acid medium
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2014.10.001

The work describes the mechanism responsible for formation of Co–Rh alloys through electroreduction of aquachloro- complexes of Co(II) and Rh(III) in an acidic chloride electrolyte. The identification of electrode reactions was performed based on voltammetric and electrogravimetric tests. Also, current efficiency of electrolysis was estimated. The electrolyte stability was tested with the use of UV–Vis spectrometry. The potential range enabling the alloy synthesis was based on electrochemical studies. The tests included influence of concentration of ∑[CoClx(H2O)6−x]2−x (x=0, 1, 2) (10 to 100mM) and ∑[RhCly(H2O)6−y]3−y (y=4, 5, 6) (10mM), electrode potential (−0.5 to −1.0V vs Ag/AgCl electrode), electrolyte pH (1 to 3) and temperature (25 to 75°C) on the composition, structure and morphology of Co–Rh alloy deposited at various potentials. The conducted tests indicate a possibility of alloy synthesis of a wide range of elemental composition and diversified morphology. The performed structural analysis showed a high influence of the synthesis conditions on the structure of the synthesized alloys.
•Electrodeposition of Co–Rh alloys from chloride solutions was investigated.•Mechanism of reactions responsible for an alloys formation was proposed.•Alloy structure, composition and morphology were analysed in relation to deposition conditions.•Influence of electrolyte composition, pH, T and E on alloy properties was studied.