Abstract
In order to contribute to the corrosion protection of aluminum alloys, silane-based hybrid coatings have been widely studied in the aerospace industry for their good adhesion to aluminum substrates, compatibility with organic paintings and to protect the underlying material, in addition to being much less toxic than the commonly used chromatization process. In this work, hybrid and inorganic sol-gel coatings were evaluated as corrosion inhibitor films for AA2024-T3 alloy. The films were characterized by linear polarization resistance (LPR) and scanning electron microscopy (SEM), which indicated that these coatings provide a lower tendency for the substrate corrosion.
Highlights
Aluminum and its alloys are among the most widely used metallic materials
Though aluminum itself has good corrosion resistance, determined by the presence of a natural oxide layer formed on its surface, aluminum alloys show improved mechanical properties, determined by the presence of alloying elements that precipitate in the form of intermetallics and cause localized corrosion
By the linear polarization results, the inorganic sol-gel coating contributes insignificantly to both the corrosion potential of the substrate and to its current density, which is attributed to the presence of cracks in the film
Summary
Aluminum and its alloys are among the most widely used metallic materials. In the aerospace and automotive sectors, their presence is justified by some of their properties, such as lightness, high fracture toughness, high fatigue performance, high moldability, increased damage tolerance and durability (Santos Junior et al 2016). Though aluminum itself has good corrosion resistance, determined by the presence of a natural oxide layer formed on its surface, aluminum alloys show improved mechanical properties, determined by the presence of alloying elements that precipitate in the form of intermetallics and cause localized corrosion This problem shows up as a consequence of the electrochemical activity difference between the intermetallic precipitate and the aluminum matrix, which is especially high in the case of copper-containing aluminum alloys (Zhang et al 2017). For these materials, the exceptional, but toxic and carcinogenic, chromatization process has been banned and a potential substitute is the hybrid silane-based coatings obtained from sol-gel process, since it provides good adhesion to aluminum and less environmental damages, with improved corrosion inhibition (Osborne, 2001). The application of inorganic and hybrid systems obtained by the sol-gel process as corrosion protection coatings for aluminum alloy 2024-T3 is the focus of this study
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