ABSTRACT
The aim of this study was to investigate the corrosion behavior of aluminum alloy AA2024-T3 substrates treated with self-assembled films obtained by combining tetraethylorthosilicate (TEOS) with ODPA (octadecylphosphonic acid)in a 0.05 mol L-1 NaCl solution. The volumetric ratios of TEOS/ethanol/water used were 4:90:6 and 4:80:16, and the corresponding films formed were denoted as 90TEOS and 80TEOS, respectively. The addition of phosphonic acid to TEOS films was tested as a way to obtain a cooperative effect in order to improve the protective characteristics of the coating. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization data showed that the 90 TEOS films in the presence of ODPA had the highest impedance modulus after 168h of immersion in chloride solution. The results obtained indicate that undoped sol-gel coatings do not provide adequate protection against corrosion, evidenced by the existence of synergism between phosphonic acid and TEOS, improving the hydrophobicity of the films.
Keywords:
Aluminum alloy; silane; phosphonic acid; EIS
