Sol-gel-derived amorphous Al2O3-ZrO2/SiO2 (AZS) and Al2O3-(Y2O3) ZrO2/SiO2 (AYZS) nanocomposite coatings were developed on stainless steel (SS) 316L specimens. The corrosion resistance of identical AZS and AYZS specimens in 5 wt.% HCl, H2SO4, and NaCl electrolytes was investigated using electrochemical polarization plots and impedance spectroscopy. The EIS results indicate that the corrosion resistance follows the order NaCl > H2SO4 > HCl, with the highest charge-transfer resistance observed in the NaCl electrolyte at low frequencies. Moreover, the lower current density observed in the NaCl and H2SO4 electrolytes suggests that the coatings were relatively crack- and defect-free, thereby providing superior corrosion protection. Surface-coating stability, degradation, and corrosion products were observed using SEM and optical microscopy. The developed silica sol-based AZS and AYZS ceramic coatings provide enhanced protection for metallic specimens in both acidic and alkaline environments.

Foreign