Enhanced Corrosion Resistance of Al Coatings on Cu Using PRC Electrodeposition from [Bmim]Cl–AlCl3

Aluminum coatings were electrodeposited on copper substrates using a chloroaluminate-based ionic liquid electrolyte composed of AlCl₃ and [Bmim]Cl, employing both direct current (DC) and pulse reverse current (PRC) modes at a current density of 5 mA/cm². Structural and surface characterizations using X-ray diffraction, field-effect scanning electron microscopy, atomic force microscopy, energy-dispersive spectroscopy, and inductively-coupled plasma optical emission spectroscopy revealed that PRC mode deposition resulted in finer grain size (29 nm), smoother surface topography (Ra ~4.2 nm), and more uniform coatings compared to DC mode (grain size 32 nm, Ra ~14.2 nm). Both deposition modes produced high-purity aluminum (>99.997%) with minimal trace impurities. Electrochemical analyses in 3.5 wt.% NaCl demonstrated that PRC mode deposited coatings exhibited improved corrosion resistance, as indicated by lower corrosion current density (0.0012 μA/cm²), higher charge transfer resistance, and reduced donor density in the passive film. These findings highlight the advantages of PRC mode electrodeposition in achieving defect-minimized, high-purity aluminum coatings with enhanced corrosion performance under low-temperature conditions.