Sustainable Ni–Al₂O₃ Nanocomposite Surface Coatings on Stainless Steel 304 for High-performance Environmental Applications

High-technology production and green material design that upgrade the surface functionality of engineering alloys are crucial for enhancing durability, energy efficiency, and long-term sustainability. Stainless steel 304 (SS304), widely used in automotive, aerospace, and marine applications, is often subjected to corrosion, wear, and mechanical degradation under severe service conditions. This study reports the development of a Ni–Al₂O₃ nanocomposite coating on SS304 using an optimized Watts bath electrodeposition process designed to achieve high-performance and sustainable surface protection. A nickel matrix reinforced with varying concentrations of nano-sized Al₂O₃ particles was employed to improve interfacial bonding, tribological hardness, and environmental stability. Key process parameters, including current density, agitation speed, deposition time, and bath composition, were systematically optimized to ensure uniform nanoparticle dispersion and the formation of defect-free coatings. Surface morphology and coating integrity were analyzed using scanning electron microscopy (SEM), while mechanical performance was evaluated through Vickers microhardness testing and pin-on-disc wear analysis. The results indicate a significant enhancement in surface hardness (by ~30–40%) and a substantial reduction in wear loss with increasing Al₂O₃ nanoparticle content, attributed to grain refinement and effective nanoparticle reinforcement. The novelty of this work lies in the combined optimization of electrodeposition parameters and nanoparticle loading to achieve a uniformly reinforced Ni–Al₂O₃ coating with superior mechanical performance using a sustainable processing route. The developed nanocomposite coating demonstrates excellent hardness, wear resistance, and extended service life, making it a promising surface engineering solution for next-generation, low-maintenance industrial applications requiring durable and environmentally responsible protective coatings.