Iron foil of approximate thickness 0.05 mm has been electroformed from an electrolyte solution, composed mainly of ferrous chloride and flowing at Reynolds numbers ranging from 1620 to 19 400. Current densities between 15 and 45 A/dm2 have been used. At low Reynolds numbers, the current efficiency for metal deposition is limited by inadequate mass transfer. As the Reynolds number is increased, the current efficiency rises to a maximum, after which the efficiency is again reduced due to excessive occurrence of a reaction involving the reduction of ferrous hydroxide to iron. The Young modulus of the material along the direction of electrolyte flow is less than the recognized value for polycrystalline iron and steel. This is because of the crystal orientation and internal stresses of the electrodeposited metal. Electrolyte flow induces hydrogen embrittlement of the foil. This condition is found to exert a greater influence than grain size on tensile strength, ductility and proof stress. Its effects can be alleviated by stress relief. The hardness is unaffected by hydrogen embrittlement, but is increased at higher Reynolds numbers, due to the formation of smaller grains. Direct heating of the cathode reduces material hardness without affecting tensile properties. The introduction of electrolyte flow raises the rate of electroforming of iron only by about 50 per cent when compared with that obtained from an unstirred electrolyte. This surprisingly small effect of flow is attributed to the slowness of the chemical reactions which have more control over the rate of deposition of iron than the rate of mass transfer.
