An in-depth comprehension of the protection mechanism of Al alloys by aniline-based silane

•Aniline-based silane studied by different experimental approaches.•Metallo-complexation related to charge transfer NH⋯N complexes in solution.•Metal–aniline interactions activated in the absence of Cl−, regardless of Al alloy nature.•Relationships between semiconducting properties and corrosion protection mechanism.

The protection mechanism of Al alloys by aniline-based silane (AnSi) was investigated by different experimental approaches. In particular, spectroscopic techniques were used for studying the chemistry of AnSi solution as a function of pH and water content, as well as in the presence of different metal ions. In addition, monitoring of structural changes of AnSi-based films deposited on different Al alloys during exposure to mild aggressive conditions (humidity and laboratory environments) was carried out. Electrochemical techniques, namely impedance measurements (Mott–Schottky analysis) and potentiodynamic polarization were applied for investigating relationships between the semiconductor behavior and the protection capacity of AnSi-based films in NaCl. Overall results converge to confirm that the protection capacity of the hybrid AnSi-based films is strictly determined by both charge transfer NH⋯N complexes and metal–aniline interactions during the surface treatment step.