Electrodeposition of Zn–Mn alloys in acidic and alkaline baths. Influence of additives on the morphological and structural properties

Abstract

Electrodeposition of Zn-Mn alloys on steel was achieved using alkaline pyrophosphate-based baths or acidic chloride-based baths. Cyclic voltammetry was used to determine the potential ranges where the various redox processes were taking place. It appeared that the reduction of Mn(II) was generally hidden by the other reduction reactions, especially by the hydrogen evolution reaction. Zn-Mn alloys containing up to 25 at.% Mn in the alkaline bath and 12 at.% in the acidic bath could be obtained at the cost of very low current efficiencies.The characterisation of the deposits obtained either by galvanostatic polarisation or potentiostatic polarisation was performed by Scanning Electron Microscopy and X-Ray Diffraction. Various Zn-Mn phases were obtained, depending on the current densities, the composition of the deposit and that of the electrolytic bath.Two commercial additives usually used for zinc electrodeposition, one in alkaline baths, the other in acidic baths, were tested. Their effects upon the composition, the morphology and the microstructure of the deposit were investigated.

Electrodeposition of zinc–manganese alloy coatings from ionic liquid electrolytes

“…The zinc electrodeposition might have reached its limiting current when the potential was made more negative and thus resulting in burnt deposits. It was reported by Sylla et al [16] that from an aqueous acidic bath containing 0.4M H 3 BO 3 at room temperature, zinc was deposited between -1.1 V and -1.4 V/SCE whilst manganese was deposited at potential lower or equal to -1.5 V/SCE. As the potential was reduced to -1.6 V, the deposits obtained became noncoherent, dark, rough and powdery as well as having a burnt appearance.…”

Electrochemical Reactions of Sodium 2-Ethylhexyl Sulfate Salt

“…Such properties can be achieved by adding certain organic compounds, i.e., arenes and surface-active agents to the zinc bath [1,2]. Surfactants are commonly used in zinc electrodeposition to control both the shape and size of metallic crystals and, in consequence, to obtain smooth and bright coatings [3,4].…”

Zn–Fe alloy electrodeposition from chloride bath: Influence of deposition parameters on coatings morphology and structure

“…Zinc coatings are widely used for the protection of steel structures in industry but the application conditions are more and more severe that implies an improvement of the protective and functional properties of Zn coatings. During the last decades, zinc alloys were studied in order to improve the corrosion resistance or the mechanical properties of zinc‐based coatings 1–9. Among the electrodeposited zinc alloys, Zn–Fe electrodeposited coatings present many excellent properties, such as excellent corrosion resistance (due to the nature of the zinc–iron phases), good paintability, good welding 10, and it has been considered to be an alternative for pure zinc coating for the corrosion protection of steel products 11, 12.…”