The Effect of Plasma-Polymerized Cerium-Doped Hexamethyldisiloxane Film Thickness on Corrosion Protection of L-PBF AlSi10Mg

Laser powder bed fusion (L-PBF)-manufactured AlSi10Mg components exhibit localized microstructural inhomogeneities and high surface roughness, rendering them susceptible to corrosion. This study investigates the characteristics of cerium-doped plasma-polymerized hexamethyldisiloxane (ppHMDSO) thin films deposited via atmospheric pressure plasma deposition (APPD), with emphasis on the influence of film thickness, governed by the number of deposition cycles (1, 3, and 5) on corrosion protection performance. All films incorporated cerium predominantly as CeO₂ nanoparticles within the polysiloxane matrix, as confirmed by SEM/EDXS and FTIR analyses. Film thicknesses ranged from ∼400 nm to ∼1700 nm, increasing nearly linearly with deposition cycles. Electrochemical measurements and a six-week neutral salt spray test demonstrated that a critical film thickness of ~ 900 nm (3 deposition cycles) is necessary to ensure effective corrosion protection. Thinner film (∼400 nm) exhibited incomplete substrate coverage and insufficient protection, attributed to the underlying surface roughness and porosity of the polymer network. Increasing the thickness to ~ 1700 nm yielded only marginal improvements, indicating the limited protective benefit beyond the optimal thickness. This study highlights the importance of optimizing the deposition parameters to achieve a balance between film performance and material efficiency, and demonstrates a scalable approach for improving the corrosion resistance of L-PBF AlSi10Mg components.