Tuning electroless nickel baths with surfactants to improve corrosion resistance of AZ31B magnesium alloy

Electroless nickel (EN) plating endows Mg alloys with integrated corrosion protection and electrical conductivity, making it highly promising for aerospace applications. Nevertheless, micro-galvanic corrosion induced by pinhole defects in EN platings severely restricts their practical deployment. Herein, five surfactants (sodium laureth sulfate [AES], sodium methyl ester sulfonate, sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate [SDBS]) were introduced into the EN plating bath. The plating microstructure, composition, and corrosion resistance were systematically evaluated via scanning electron microscope, energy-dispersive X-ray spectrometer, porosity tests, electrochemical measurements, and molecular dynamics (MD) simulations. Results indicated that surfactant addition remarkably reduced plating porosity, with SDBS-modified platings achieving zero porosity in 5 wt% NaCl solution. Electrochemical tests confirmed that SDBS-based EN platings exhibited the highest charge transfer resistance (8.201 × 10³ Ω·cm²) and corrosion inhibition efficiency (83.3%), outperforming other surfactants. MD simulations revealed that all surfactants spontaneously adsorbed on the Ni (111) surface, while excessive adsorption strength (e.g. AES) hindered Ni²⁺ deposition and compromised plating quality. This work provides a facile and effective strategy to tailor EN plating performance via surfactant modification, facilitating the reliable application of Mg alloys in aerospace environments.