Testing the role of metal hydrolysis in the anomalous electrodeposition of Ni-Fe alloys

With the objective of testing several models of the ''anomalous codeposition'' (ACD) encountered in the electrodeposition of nickel-iron alloys, the effects of bath pH and complexing agents on the composition of deposits were examined. When the pH of the ''base line'' bath was increased from 3.0 to 5.0, the Ni/Fe mass ratio of the deposit increased (i.e., the deposition became less anomalous). The presence of tartrate ion in the bath produced a slight decrease in the Ni/Fe of the deposit. This complexing agent complexes ferric ion and thus prevents its precipitation but has little interaction with ferrous ion or nickel ion under the electrodeposition conditions examined. The addition of ethylenediamine to the bath produced a significant increase in the Ni/Fe mass ratio. This complexing agent does not interact significantly with ferric ion or ferrous ion under the test conditions. None of these observations are consistent with the Dahms and Croll model of ACD. The effects of pH and tartaric acid on the deposit composition are consistent with the predictions of the Grande and Talbot model and the Matlosz model. The effect of ethylenediamine is not consistent with the Grande and Talbot model, but may be interpreted within the framework of the Matlosz model and the Hessami and Tobias model.