Marianna Orrico

The urgent need to reduce the environmental footprint associated with aircraft manufacturing, particularly by replacing hexavalent chromium Cr(VI), has become a priority of the recent EU legislation and the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) directives. In this studying, the corrosion performance of a Cr(VI)-free metal-based primer (MBP), applied to properly treated aluminium alloy surfaces, was investigated by comparing four different surface treatments: tartaric sulphuric anodising (TSAA) and phosphoric acid anodising (PAA), as eco-friendly alternatives, chromic acid anodising (CAA) and chromate chemical conversion (CCC) as traditional methods. The influence of the pre-treatments on the surface morphology, chemical oxide layer, wettability, adhesion and corrosion resistance was systematically evaluated by scanning electron microscopy (SEM), metallographic analysis, energy dispersive X-ray spectroscopy (EDS), confocal microscopy, contact angle measurements, adhesion tests, electrochemical impedance spectroscopy (EIS), salt spray testing (SST) and accelerated corrosion testing (ACT). This study shows that anodising treatments modify surface porosity, oxide thickness, and wettability, which can directly impact corrosion protection. The analysed results highlight that Cr(VI)-free anodising treatments, particularly PAA and TSAA, combined with a MBP, can provide corrosion protection comparable to traditional chromate-based systems, offering a viable and environmentally sustainable alternative for aerospace applications.

The corrosion of metal surfaces is one of the most critical issues in aviation, where aircraft are subjected to very extreme climatic and operating conditions. Hexavalent chromium, Cr (VI), based coatings provide an effective corrosion protection at relatively low cost, but unfortunately their usage has a significant impact on the environment. To comply with new regulations (REACH) and to ensure effectiveness against corrosion, the current interest of researchers and investors is focused on the synthesis and the design of eco‐friendly and safer coatings, to develop an alternative and innovative corrosion protection coating systems, characterized by specific performance in terms of good adhesion, barrier, and rheological properties. The development of innovative materials and the implementation of new technologies can allow widening the safety window in all the process phases from the production to the disposal. These research activities are focused on the development of anticorrosive and chromate‐free coatings, by modifying metal‐based primer formulations. The aim is toward the improvement in the anticorrosive performance and durability respect to the systems already known in the literature through the incorporation of sustainable compounds or less toxic metals as corrosion inhibitors to reduce the environmental impact.