Tuning wear and corrosion resistance of carbon steel by controlling EPD parameters for Ni–Cr oxide nanocomposite coatings

Metal oxides play a crucial role in engineering nanocomposites, offering enhanced surface performance for metals in demanding industrial applications. In this work, Ni – Cr oxide nanocomposites were synthesized via co-precipitation and deposited onto carbon steel (St12) substrates using electrophoretic deposition (EPD) under varying coating times (1–3 min) and voltages (100–120 V), followed by sintering at 750°C. Structural, morphological, and chemical characteristics were analyzed using XRD, FTIR, TEM, FESEM, and optical microscopy (OM). The as-synthesized nanocomposite comprised NiO and NiCr2O4 phases with an average crystallite size of 28.8 nm. After sintering, the coatings contained Ni, Al, NiAl2O4, and NiCr2O4 phases. Mechanical and electrochemical performances were assessed through microhardness, ball-on-disk wear, electrochemical impedance spectroscopy (EIS), and polarization tests. Coatings substantially improved hardness, wear resistance, and corrosion resistance compared to bare St12. The 100 V–3 min coating exhibited the highest wear resistance (mass loss = 1.2 mg), whereas the 120 V–3 min coating showed the lowest (2.0 mg). The coating with a current density of 8.7 µA·cm− 2 demonstrated the lowest corrosion rate, while EIS analysis revealed that the 110 V–3 min sample achieved the highest total resistance (Rt=7934.6 Ω), far surpassing the uncoated substrate (Rt=134.49Ω). Equivalent electrical circuit modeling provided insight into the corrosion mechanisms of all tested samples.