Effects of silica and Ag on the electrochemical behavior of titania-based nanocomposite coatings deposited on 2024 aluminum alloy by the sol-gel method

To enhance the service lifetime and effectiveness of Al 2024-T4 in medical applications, the corrosion and wear characteristics can be improved by deposition of ceramic coatings. Herein, titania, titania-Ag and titania-silica-Ag nanocomposite coatings are deposited on 2024 aluminum substrate by the sol-gel and dip-coating techniques and the corrosion behavior is investigated in 0.05 M NaCl, 0.5 M NaCl, and Ringer's solutions. The adhesion strength and thickness of the coatings decrease from 23 to 19 mN and 516 to 508 nm, respectively, with addition of Ag, but increase from 23 to 28 mN and 516-547 nm, respectively, when silica is added. Owing to the formation of favorable protective layers, the corrosion resistance of the titania-silica-Ag coating is better than that of the other two coatings. The presence of calcium and potassium ions leads to more rigorous reactions on the surface and formation of a protective compact oxide layer on 2024 aluminum substrate.