Electrodeposition of manganese layers from sustainable sulfate based electrolytes

• Published in: Surface & coatings technology Vol. 334; pp. 261 - 268
• Main Authors: Fernández-Barcia, Mónica, Hoffmann, Volker, Oswald, Steffen, Giebeler, Lars, Wolff, Ulrike, Uhlemann, Margitta, Gebert, Annett
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 25-01-2018; Elsevier BV
• Subjects: (NH4)2SO4; Aqueous electrolytes; Biodegradability; Chemical vapor deposition; Corrosion prevention; Electrodeposition; Electrolytes; Electronegativity; Energy conversion; GD-OES; Hydroxides; Manganese; Manganese base alloys; Manganese compounds; Medical devices; Medical electronics; Mn electrodeposition; pH control; Studies; Sustainable electrolyte; X ray photoelectron spectroscopy; XPS; pH control; XPS; Mn electrodeposition; GD-OES; (NH4)2SO4; Sustainable electrolyte
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2017.11.028

Functional manganese-(Mn)-containing layers are becoming increasingly important in the fields of sacrificial corrosion protection, biodegradable medical devices or electrochemical energy conversion systems. Electrodeposition can be a low cost and time-efficient production route, but the very electronegative nature of Mn makes this reduction process quite challenging.
In this paper, electrolytic potentiostatic deposition of metallic Mn layers from environmentally friendly aqueous manganese sulfate electrolytes with pH3 is successfully demonstrated. A continuous electrolyte flow in the cathodic compartment of the electrochemical cell for controlling the pH value during deposition was found to be essential for achieving good layer qualities. Based on cyclic voltammetry analysis in combination with quartz crystal microbalance measurements a suitable deposition potential range was identified. The obtained electrodeposited layers were characterized by means of SEM, XRD, GD-OES and XPS. The shift of the deposition potential from −2.4 VMSE to −2.6 VMSE (deposition time 60min) yields a thickness increase of the metallic α-Mn deposits from <500nm to ~2μm. Only thin additional surface regions of Mn-oxides/-hydroxides were identified. The important role of (NH4)2SO4 as complex-forming electrolyte additive is discussed and an impact of the salt concentration on the deposit properties is revealed. This is a promising starting point for further Mn alloy deposition analysis.
•Electrodeposition of metallic Mn at potentials −2.4, −2.5 and −2.6 VMSE•pH control via electrolyte flow conditions•(NH4)2SO4 concentration impacts deposit morphology, structure and chemistry.