ANOMALOUS ELECTRODEPOSITION OF NICKEL-IRON

Experiments to study anomalous codeposition of iron and nickel were conducted from 0.5M NiSO4 and 0.5M FeSO4 solutions with pH adjusted to 3 with H2SO4, using a rotating disk electrode. The effect of adding 0.01M B(OH)3 to the plating bath was also investigated. Anomalous codeposition occurred for all electrode rotational speeds and applied potentials considered. Boric acid was found neither to affect alloy deposition current efficiency, nor to eliminate anomalous codeposition for the experimental conditions investigated. Cyclic voltammetry indicates that a borate complex formed at -1.0 V vs. SCE when boric acid was added to the plating bath. A model used to evaluate the surface pH from the experimental results shows that a sudden rise in pH is not necessary for anomalous codeposition to occur and that boric acid does not act as a buffer during codeposition of NiFe.