Electrodeposition of iron coatings from methanesulfonate electrolyte

The electrodeposition of iron coatings from aqueous solutions based on methanesulfonate (Fe(CH3SO3)2) and sulfate (FeSO4) electrolytes was investigated with the aim of developing a "green" technology for producing nanocrystalline coatings with enhanced mechanical and corrosion-resistant properties. The influence of key process parameters (current density, temperature, and pH) was assessed in terms of current efficiency, microstructure, microhardness, and corrosion resistance of the coatings. Under otherwise identical conditions, the current efficiency in the methanesulfonate electrolyte is significantly higher than in the sulfate one, reaching 95–96%. Polarization measurements indicated that the notable increase in current efficiency is due to the higher overpotential of the concurrent hydrogen evolution reaction during electrodeposition from the methanesulfonate medium. The average crystallite size of iron coatings deposited from the methanesulfonate electrolyte ranged from 55 to 80 nm, whereas submicron-sized crystallites were formed in the sulfate-based coatings. The microhardness of the coatings obtained from the methanesulfonate electrolyte increased from 461 to 477 kg/mm2 with an increase in current density from 5 to 25 A/dm2, significantly exceeding the values typical of coatings from the sulfate solution. Corrosion tests in 3% NaCl solution demonstrated a considerably more positive corrosion potential, lower corrosion current, and higher polarization resistance for coatings from the methanesulfonate electrolyte. Thus, the use of methanesulfonate electrolyte for iron plating ensures higher current efficiency, increased microhardness, and a significant improvement in the corrosion resistance of the resulting electroplated coatings, making it promising for protective applications in corrosive environments and opening up new opportunities for the restoration of components and assemblies in aviation equipment.