1. Introduction
The aluminium alloy 2024 properties, such as high strength-to-weight ratio, good fracture toughness and low cost, have
maintained its dominant position in aerospace industry [1]. This kind of aluminium alloy has a complex distribution and
composition of intermetallic particles. It is well known that corrosion process initiate in intermetallic particles, specifically
in the S-phase with preferential dissolution of Al and Mg [2,3]. The localized corrosion constitutes the main degradation form of this alloy [2,4,5]. According to some authors the formation of stable pits evolves the cooperative mechanism, by galvanic coupling of intermetallic particles [6]. The cooperative corrosion process comprise the appearance and development of corrosion rings, whose intern surface act predominantly as a cathode and drives the anode into the surface, resulting in the grain boundary network. The grain boundaries attack evolves into an intergranular
attack, leading to mechanical failure of this aluminium alloy [7]. One of the most important methods for corrosion protection is the employment of organic coatings, such as anticorrosive paints. A key feature in lifetime of organic coatings is its adhesion with the metal surface when exposed to corrosive medium [8], i.e., the adhesion is one of the fundamental properties for a good corrosion protection. The physical-chemistry properties in the interface between metal and paint are usually improved by a pretreatment. The chromatization was a pretreatment widely used for light metals such as aluminium and its alloys, especially in the aerospace industry [9] due to its role as both anchoring for the organic coating and as corrosion inhibiting system. Nevertheless, the environmental restrictions have forbidden its utilization. In this context, the sol–gel process based on silica precursors are able to form bonds with both metal substrate and reactive groups of organic paint thought their functionalized organic group, due to silane bifunctionality [10]. Thus, as silane films assist the interaction and adhesion with ensuing organic coating layer,