Effect of near-surface pH on electrodeposition of iron and permalloy

Abstract

Anomalous codeposition of alloys appears to be related to the local pH rise at the cathode surface, which results from the simultaneous H2-evolution reaction. Near-surface pH measurement was employed to investigate the pH at the cathode during iron and NiFe electrodeposition. The effects of ferrous ion, ferric ion and boric acid on the pH were examined. It is shown that ferrous chloride solutions exhibit buffering action at lower pH than nickel chloride solutions. Small concentrations of ferric chloride exhibit the same surface pH as large concentrations of ferrous chloride solutions containing traces of ferric. This suggests that hydrolysis and precipitation of ferric ion may be determining the surface pH and may be influencing the rates of Ni and Fe electrodeposition.