Microstructural aspects of manganese metal during its electrodeposition from sulphate solutions in the presence of quaternary amines

•Quaternary amines produced smooth and bright manganese electrodeposits.•TEABr produced smooth and bright deposits with euhedral shaped crystals.•TBABr produced dendritic deposits with elongated poly-nodular crystals.•All the quaternary amines behaved as cathode polarisers.•TEABr was found to be the most efficient organic additive. In the present study investigation was made on the electrodeposition of manganese from sulphate solutions in the presence of quaternary amines TEABr, TPABr and TBABr. The concentrations of these additives were varied over a relatively broad range to evaluate their effect on the deposit morphology and preferred crystal orientations of the electrodeposited metal. TEABr resulted in bright and smooth manganese electrodeposits giving euhedral shape to the crystals with distinct triple junction points. TPABr also showed similar results at lower concentrations. However, TBABr resulted in the formation of dendritic growths with elongated poly-nodular crystals similar to that of Paragorgia corals having uniform multistep growths. The presence of these quaternary amines in the electrolyte causes polarisation of the cathode. TBABr being the strongest cathode polariser adsorbs strongly on the cathode resulting in poor deposit quality. TEABr was found to be the most efficient additive producing the desired quality manganese electrodeposit.