Study of Post-World War II French Aeronautical Aluminium Alloy and Coatings: Historical and Materials Science Approach

In many countries, collections of historic aircraft, conserved in Air and Space museums or local associations, reflect the importance of a national or local history. Mostly parked outdoors, aircraft suffer from significant corrosion requiring conservation operations. During renovation, metallic parts are often replaced by association members. This can lead to a major loss of information since industrial archives dealing with materials and processes do not always survive. However, if these elements can be considered, they could be a fundamental source of information on the materials originally used and of the technical history of aeronautics. This work reports a thorough study of aluminium-based alloy parts collected on a Breguet aeroplane dating from the 1950s, during its recent renovation. Thanks to an approach coupling multi-scale material characterisation and research in archives, information on the industrial knowledge is revealed. Several historic grades of aluminium-based alloys were found, namely A-U4G, A-U4G1, and A-U3G, depending on the role of the part. Similarly, different protective coatings were identified (anodic oxidation, primers, and paintings), depending on the role of the metallic part and its location in the plane. Knowledge of the materials from bulk metal to the coated surface is necessary for good conservation practices regarding aeronautical heritage artefacts. Related documents and archives also fundamentally help in understanding such complex artefacts.