Enhancement of protection of aluminum through dopamine impregnation into hybrid sol–gel monolayers

The present work involves the incorporation of dopamine (DA) into the hybrid sol–gel monolayers (Hy) consisting of (3-glycidoxypropyl)methyldiethoxysilane and Tetraethyl orthosilicate. The resultant doped hybrid layers coated over aluminum surface was characterized by FT-IR, UV–Vis, XRD, EDX and SEM analyses. The corrosion behavior of bare and coated aluminum substrates in 3.5 % NaCl medium was examined by cyclic voltammetry, potentiodynamic polarization and electrochemical impedance spectroscopy techniques. Results from the electrochemical measurements showed that the DA impregnated Hy sol–gel monolayers offered better corrosion protection with superior coating thickness than the Hy sol–gel monolayers without DA. The enhancement of protection could be attributed to the fact that DA promote the formation of strongly bonded and densely packed monolayer films, which show better adhesion than the conventional silane systems.