A study of external magnetic-field effects on nickel–iron alloy electrodeposition, based on linear and non-linear differential AC electrochemical response measurements

Linear and non-linear electrochemical AC spectrometry (the former better known as electrochemical impedance spectrometry, EIS) studies were performed during Ni–Fe alloy electrodeposition in magnetic fields up to 0.5 T. We could show that by using linear EIS it can be very difficult – if not almost impossible – to identify magnetohydrodynamic effects on the electrodeposition of Ni–Fe alloys. Very poor reproducibility was seen in linear EIS experiments, even in the absence of a magnetic field, due to the inherent non-stationarity of electrocrystallisation processes. Using a non-linear approach we could show that the real and imaginary parts of the total impedance of the system are sensitive to the presence of a magnetic field in the frequency range from 1 to 100 Hz. Some degree of correlation between the applied magnetic field and the second harmonic response of the current density could also be detected at relatively high frequencies (e.g., at 10 and 100 Hz).