Surface finish-dependent stability of stainless steel under long-term cleaning, disinfection and sterilization process: AISI 420 in medical applications.

BACKGROUND

Reusable stainless-steel medical devices are subjected to repeated cleaning, disinfection, and sterilization processes that may progressively alter surface properties, potentially affecting durability, and clinical performance.

METHODS

The long-term effects of up to 1000 processing cycles were investigated on AISI 420 (American Iron and Steel Institute grade 420) stainless steel samples with two surface preparations: mechanically brushed (MB) and glass bead -blasted (GBB). Surface roughness (Ra, Sa, Sq), wettability (contact angle), microhardness, and surface morphology were evaluated before and after processing using profilometry, contact angle measurements, microhardness testing, and SEM/EDX analysis.

RESULTS

GBB surfaces consistently exhibited higher roughness (Ra ≈ 0.58 µm) than MB surfaces (Ra ≈ 0.42-0.46 µm) and remained more hydrophilic, with significantly lower contact angles (≈ 40-50°) compared to MB samples (≈ 65-70°). Microhardness values were higher for GBB samples (≈ 820-870 HV0.05) than for MB samples (≈ 680-705 HV0.05) across all processing cycles. However, SEM/EDX analysis revealed more frequent oxidation-related dark spots on GBB surfaces after extended cycling, indicating increased susceptibility to surface discoloration.

CONCLUSIONS

Surface preparation has a significant influence on the long-term stability and performance of reusable stainless-steel medical devices. While glass bead-blasted surfaces offer higher hardness and wettability, they may be more prone to oxidation-related discoloration during prolonged reprocessing, with potential implications for infection prevention and device longevity.