Development of CuO–ZnO–20%NiO ternary nanocomposite coatings for durable and antibacterial St12 steel surfaces

CuO-ZnO-20%NiO nanocomposite coatings were synthesized by co-precipitation and deposited on St12 low-carbon steel via electrophoretic deposition at different voltages (90–110 V) and deposition times (8–16 min). The novelty of this study lies in incorporating 20% NiO into conventional CuO-ZnO to develop a multifunctional ternary coating with enhanced antibacterial performance that simultaneously provides excellent corrosion and wear protection for St12 steel compared with the binary CuO-ZnO coating. Structural, antibacterial, wear, and corrosion properties were evaluated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), ball-on-disk testing, polarization Tafel analysis, and electrochemical impedance spectroscopy (EIS). The ternary CuO-ZnO-20%NiO coating showed stronger antibacterial activity than CuO-ZnO, with minimum inhibitory concentration (MIC) values of 0.298 and 0.276 mg/mL and minimum bactericidal concentration (MBC) values of 0.481 and 0.671 mg/mL against Gram-positive and Gram-negative bacteria, respectively. Excessive deposition conditions (110 V–12 min) produced high porosity and reduced wear performance. All coated samples exhibited improved corrosion resistance compared with bare St12 steel. The optimized coating (100 V–12 min) achieved the highest corrosion resistance (charge transfer resistance (Rct) = 29961 Ω·cm2 vs. 73.89 Ω·cm2 for bare St12) and improved wear resistance by 47%. These results demonstrate the potential of CuO-ZnO-20%NiO coatings for enhancing St12 steel in bacteria-prone environments.