Electrochemical Corrosion Characteristics of Silica Sol‐Derived Alumina‐Zirconia and Alumina‐Yttria Stabilized Zirconia Amorphous Nanocomposite Coating

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Abstract
Sol‐gel‐derived amorphous Al 2 O 3 ‐ZrO 2 /SiO 2 (AZS) and Al 2 O 3 ‐(Y 2 O 3 ) ZrO 2 /SiO 2 (AYZS) nanocomposite coatings were developed on stainless steel (SS) 316L specimens. The corrosion resistance of identical AZS and AYZS specimens in 5 wt.% HCl, H 2 SO 4 , and NaCl electrolytes was investigated using electrochemical polarization plots and impedance spectroscopy. The EIS results indicate that the corrosion resistance follows the order NaCl > H 2 SO 4 > 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 H 2 SO 4 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.

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