One of the pillars of developed economics is modern transport, where there is always a high demand for the elaboration of lightweight efficient vehicles and transport facilities. Aluminum and magnesium alloys encounter continuously increasing applications in high-performance aircraft, automobile, and marine vehicles. Various advanced multilayered corrosion protective coating systems have recently been proposed to provide a reliable long-term corrosion protection combined with a number of supplemental beneficial properties. The present brief review is an attempt to summarize the basic trends and concepts regarding the elaboration of environmentally friendly multilayered and multifunctional corrosion protective coating systems. Our work summarizes these recent trends, including recently accepted environmental requirements. We have also distinguished the concepts for active and passive corrosion protection capabilities. The basic approach for the achievement of efficient active corrosion protection properties are outlined with suitable examples, such as inhibitor incorporation into ceramic or carbon nanoparticles, encapsulation of active self-healing compounds, reinforcing phase involvement and coating, finished by ultraviolet absorbers and hydrophobic compounds. As a main result, an entire conceptual model has been proposed based on the state-of-the-art analysis.

The current research presents results following corrosion tests, performed on combined anodic alumina/cerium conversion coatings (Al 2 O 3 /CeCC), thermally sealed for 15 min at 100°C either in boiling water or in hot-air medium. The coatings were formed on AA2024-T3 aircraft alloy substrates, at the optimum conditions of anodization and cerium conversion coating deposition, described in previous works. Prior to the corrosion tests, both the color characteristics and wetting ability of the combined films were evaluated. The corrosion protective properties of the sealed films were assessed by means of Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP). The measurements were performed after 672 hours of exposure to a 5 % NaCl model corrosive medium (MCM). Additional long term (up to 1344 hours of exposure) durability tests were then performed under the same conditions for the samples and superior performance was established. The electrochemical measurements were conducted regularly, once a week. Low-and high-resolution Scanning Electron Microscopy (SEM) studies were performed on selected samples. The experimental results have shown that the sealing procedure in an aqueous environment enhances the corrosion protective ability and durability of the coating, probably due to formation of a hydrate layers, that suppresses the access of corrosive species to the surface of the substrate. This inference was additionally confirmed by the subsequent chemical analysis by means of X-Ray Photoelectron Spectroscopy (XPS). The results acquired have also shown that the incorporated Ce is predominantly in the form of Ce(IV)-oxides/hydroxides and after the thermal treatment almost entirely consists of cerium.