The effect of combined annealing and temper-rolling treatments on the microstructure and corrosion properties of nickel electroplated coating

Nickel coatings are widely used for corrosion and wear resistance, often undergoing post-treatment to enhance performance. Depending on their final application, Ni-coated steel may be subjected to mechanical forming processes to produce cylindrical can shapes, commonly used as battery cases or food storage containers where corrosion resistance is critical. Before mechanical forming, a key thermomechanical process called temper rolling is applied to improve coating adhesion, reduce residual stress, and minimize surface defects. This study systematically investigates the corrosion mechanisms of Ni-electroplated steel after annealing and temper rolling, demonstrating that both processes enhance localized corrosion resistance by modifying microstructure, surface morphology, and surface oxide evolution. These treatments promote passivity by increasing NiO content relative to Ni(OH)₂, significantly improving charge transfer resistance. Additionally, iron diffusion from the steel substrate generates an electrical surface potential gradient within the coating, affecting nobility variations across different regions. Post-corrosion analysis of temper-rolled samples reveals that corrosion initiation occurs at submicron grains, where structural gaps facilitate substrate exposure, underscoring the role of processing routes in enhancing coating durability.