Mechanism of Electrodeposition of Manganese in Alpha and Gamma Modifications

Abstract

A mechanism of the deposition of manganese in alpha and gamma modifications, in the presence and absence of addition agents in the electrolyte, has been proposed based on experimental results and evidence. A flash layer of amorphous manganese is deposited from pure solutions, over which gamma manganese begins to build up in the absence of reducible sulfur or selenium compounds in the electrolyte. In the presence of sulfur dioxide, the amorphous nature continues to build up to an increasing thickness over which crystalline alpha manganese is obtained. Alpha manganese is obtained in the presence of sulfur, selenium, or tellurium when the cathode polarization together with the hydrogen content of the deposit is found to be increased. Likewise, the increase in current density increases the cathode polarization together with the hydrogen --ntent of the deposit when hard brittle amorphous manganese is obtained. The low hardness and density of electrodeposited alpha manganese, compared to its annealed state, and the increase in hardness together with ductility on heating, suggest that a part of the discharged hydrogen ions assumes positions inside the lattice or forms a complex during the deposition of alpha manganese.