Impact of electroless ZnO, SiC, and Al2O3 reinforced Ni-P coatings on brake pad properties

Electroless Ni-P coatings are ideal for automotive steel components, such as brake pads, as they offer exceptional adhesion, corrosion resistance, and hardness. In this study, duplex coatings were developed by combining zinc oxide (ZnO), aluminum oxide (Al₂O₃), and silicon carbide (SiC) nanoparticles in four different forms: Ni-P-ZnO/SiC, Ni-P-SiC/ZnO, Ni-P-Al₂O₃/SiC, and Ni-P-SiC/Al₂O₃. These coatings were subjected to an annealing process at 200°C for 120 min in order to assess the impact of heat treatment. XRD, SEM, Vickers hardness experiments, and potentiodynamic polarization in a 3.5% NaCl solution were employed to evaluate the corrosion behavior, microhardness, and surface roughness. Although Ni-P-SiC/Al₂O₃ coatings exhibited the highest microhardness (37% increase), the results indicated that Ni-P-Al₂O₃/SiC coatings had the lowest surface irregularity (0.74 μm). Ni-P-ZnO/SiC coatings demonstrated superior corrosion resistance with a corrosion potential of -490 mV. The coatings exhibited an increase in crystallinity following annealing, which subsequently enhanced their corrosion resistance and hardness.