Vertical vapor phase growth of silver in a sealed quartz tube: Substrate-dependent morphologies on galvanized steel and 316L stainless steel

Sealed-tube vertical vapor phase growth (VVPG) provides a closed-system route for silver (Ag) deposition with minimal liquid waste. This study evaluates substrate-dependent Ag morphologies on galvanized steel (GS) and 316L stainless steel (SS316L) rods in the furnace transition zone (TZ), using quartz-wall (QW) condensates as witness deposits, characterised by SEM/EDS and XRD. SEM/EDS confirmed heterogeneous, discontinuous Ag-rich domains with distinct architectures on Rod–GS–TZ versus Rod–SS–TZ, indicating substrate-controlled nucleation. QW deposits indicate evaporation–transport–condensation, and XRD reveals reflections compatible with fcc-Ag. Preliminary agar diffusion screening (37 °C, 24 h; n = 3 per measurable condition) revealed inhibition limited to GS-associated specimens: Rod–GS–TZ produced a 4.65 ± 0.88 mm halo against Escherichia coli, while QW–GS–TZ yielded 1.15 ± 0.48 mm against E. coli, 3.23 ± 0.49 mm against Staphylococcus aureus, and 1.62 ± 0.23 mm against Candida albicans. Corrosion resistance was assessed separately, on a paint-coated barrier system prepared by mixing Ag-containing sediment from the VVPG-treated quartz-wall deposits into the paint before application, rather than coating the bare Ag/VVPG surfaces directly. Electrochemical screening in 3.5 wt% NaCl (manual Tafel, n = 3) reduced corrosion rates from 0.555 ± 0.126 mm·year⁻¹ (uncoated) to 0.254 ± 0.022 mm·year⁻¹ (paint-coated) and 0.0987 ± 0.0065 mm·year⁻¹ (paint-coated + Ag/VVPG), with mean E_corr of −0.676 ± 0.086 V, −0.358 ± 0.124 V, and −0.436 ± 0.023 V. Overall, sealed-tube VVPG enables substrate-dependent Ag deposition, providing preliminary evidence of selective antimicrobial response and improved, though not yet statistically resolved, corrosion performance for a paint-coated Ag/VVPG system relative to paint alone.