The effect of alkaline etching time on the anticorrosion performance of vanadia film formed on high strength AA2024 in chloride media |
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Authors: | Abdel Salam Hamdy I Doench H Möhwald |
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Affiliation: | 1.Central Metallurgical Research & Development Institute (CMRDI),Helwan, Cairo,Egypt;2.Max Planck Institute of Colloids and Interfaces,Potsdam,Germany |
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Abstract: | Corrosion performance, morphology, and electrochemical characteristics of vanadia-based conversion coatings on high strength
aluminum AA2024-T3 alloy were examined as a function of alkaline etching time prior to vanadia treatment. Corrosion resistance
and coating performance improved after etching in an alkaline solution for 10 min followed by vanadia treatment at room temperature.
Electrochemical impedance spectroscopy and polarization testing correlated to macro- and microscopic surface examination and
visual inspection. Proper etching of aluminum AA2024-T3 panels in alkaline solution prior to vanadia coating is a time dependent
and considers a critical step for improved coating performance and materials durability. Results showed that the optimum alkaline
etching time prior to vanadia treatment was 10 min which offers the best resistance to localized corrosion attack in NaCl
solution. Alkaline etching for 10 min has an important role in increasing the number of OH groups on the aluminum surface,
contributing to the adhesion of the vanadia-rich aluminum oxide layer by promoting covalent bonding. Based on these results,
processes active during alkaline etching are kinetically dependent and strongly influenced by etching time. |
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