Tuning Nanocrystalline Heterostructures for Enhanced Corrosion Resistance: A Study on Electrodeposited Ni Coatings

Tailoring the microstructural heterogeneity of metallic coatings is a promising strategy for enhancing their corrosion resistance; however, its systematic optimization remains underexplored. Here in, we present a one-step, scalable electrodeposition strategy to fabricate Ni coatings with tunable nanocrystalline heterostructures on Cu substrates by varying the current density from 1 mA/cm2 to 50 mA/cm2. The coating with a current density of 10 mA/cm2, featuring a heterogeneous nanograin structure of coexisting small and large grains, exhibited optimal corrosion resistance in 3.5 wt.% NaCl solution, with a low self-corrosion current density of 4.48 µA/cm2. Electrochemical impedance spectroscopy (EIS) and molecular dynamics (MD) simulations revealed that the heterostructure dispersed Cl− adsorption sites and promoted passivation. High-resolution transmission electron microscopy (HRTEM) revealed that as the current density increased from 10 mA/cm2 to 50 mA/cm2, the corrosion product transitioned from a crystalline NiOOH structure to an amorphous structure, which correlated with a reduced corrosion resistance. The heterogeneous microstructure enhances durability, offering a cost-effective and alloy-free alternative for offshore applications. These findings provide a theoretical and experimental basis for designing advanced corrosion-resistant coatings.