Influence of LSP on The Electrodeposited Nickel Coating for The Improvement of Electrochemical Behaviour

Abstract

Nickel coatings were prepared on a copper substrate using the electrodeposition technique, which often leads to the formation of pores and microcracks that deteriorate surface integrity. To overcome these limitations, this study investigates the effect of Laser Shock Peening (LSP) on the surface morphology, scratch resistance, and electrochemical behaviour of the Ni coating. The LSP treatment markedly improves interfacial bonding strength, leading to a more compact, defect-free, and densified coating microstructure. The residual stress increased from –27.9 MPa to –657 MPa (higher compressive), without any phase transformation as confirmed by XRD. The LSP-treated nickel coating showed a 204.38% increase in hardness compared to the unpeened sample, primarily due to the formation of a work-hardened severe plastic deformation layer on the coated surface. Its scratch resistance was markedly improved, showing reductions of 56.07% in penetration depth and 19.37% in scratch width, along with increases of 53.87% in scratch hardness and 121.23% in critical load. These enhancements are attributed to grain refinement, and the formation of a hardened surface layer induced by LSP treatment through mechanical interlocking of coating with substrate. Furthermore, the generation of CRS, increased dislocation density, and grain refinement led to the formation of a denser and stable early passive film formation. This film effectively inhibited crack propagation and restricted electrolyte penetration, resulting in a lower corrosion current density and enhanced corrosion resistance after LSP treatment. Overall, this study establishes an experimental foundation for employing LSP to enhance the performance and durability of Ni-based coatings in industrial protective applications.