Suppression of hydrogen-induced pinholes in ultra-thick electroless Ni-P coatings via interfacial regulation using sodium lauryl ether sulfate

Achieving pinhole-free ultra-thick (>120 μ m) electroless nickel-phosphorus (Ni-P) coatings for precision machining is hindered by hydrogen bubble entrapment. This study demonstrates that sodium lauryl ether sulfate (SLES) effectively suppresses hydrogen-induced pinhole formation by modulating the liquid–solid interface. Compared to surfactant-free and conventional sodium dodecyl sulfate (SDS) baths, the optimal addition of SLES dramatically reduced pinhole density from ∼42 to ∼3 pinholes/dm² while maintaining high deposition rates. Contact angle measurements revealed that SLES significantly improved interfacial wettability (reducing the angle to 15.5°), facilitating rapid bubble detachment. Crucially, molecular dynamics (MD) simulations and X-ray photoelectron spectroscopy (XPS) elucidated the underlying atomic-level mechanism. Unlike SDS, which forms a rigid adsorption layer leading to localized chemical heterogeneity and stress accumulation during prolonged deposition, SLES achieves a dynamic, moderate adsorption state. This distinct interfacial regulation promotes spontaneous bubble detachment and preserves the amorphous structural integrity. This work establishes SLES as a superior interfacial modifier, providing a theoretical basis for fabricating defect-minimized, ultra-thick Ni-P coatings.