Influence of pulsed waveform parameters on the microstructure and electrochemical corrosion resistance of electrodeposited Ni–Sn alloy coatings

Abstract This study systematically compares the microstructural characteristics, surface morphology, and corrosion resistance of Ni-Sn alloy coatings electrodeposited using direct current (DC) and pulse current (PC) methods. The influence of waveform geometry – including triangular, rectangular, sinusoidal, and ramp configurations – on coating properties was comprehensively characterized through microhardness testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) analyses. These techniques respectively evaluated the mechanical properties, phase composition, morphological features, and electrochemical corrosion behavior of the deposited coatings. X-ray diffraction (XRD) analysis revealed that the coatings consisted predominantly of the Ni₃Sn₂ intermetallic phase. Scanning electron microscopy (SEM) examination demonstrated that the Ni-Sn coating deposited using PC current exhibited superior surface uniformity but lower density compared to the direct current (DC) deposited coating. Microhardness measurements showed an increase from 238 HV (DC) to 297 HV for the ramp-wave PC coating. Electrochemical impedance spectroscopy revealed substantial improvements in charge transfer resistance (Rct), with PC-deposited coatings showing increases of 1570% (ramp), 554% (sinusoidal), 324% (triangular), and 83% (rectangular) relative to DC coatings. Correspondingly, potentiodynamic polarization measurements demonstrated that the corrosion current density (icorr) was reduced by factors of 14.5 (ramp), 3.2 (sinusoidal), and 2.9 (triangular) compared to the DC-deposited coating. Ultimately, PC plating yielded Ni-Sn alloys with improved corrosion resistance across all waveforms (ramp, sinusoidal, triangular, DC). This suggests promise for these advanced coatings in microelectronics and energy storage. Graphical Abstract