Analysis of original chromate-based primers for aluminium alloys' protection collected on heritage aircraft

The remains of historical paints applied on heritage aircraft (wrecks from World War II or collection) are invaluable witness of techniques developed bymanufacturers to preserve aircraft structures from corrosion. The primer, i.e. first layer applied on the Al substrate, contains anticorrosionpigments (chromates). We are studying the chemical processes involved in the formation of the protective layer, involving zinc chromates mixed or notwith complex phosphates on Al alloy. A close investigation of the nature of the formedcompound (Cr, Zn, P, O) is necessary. XRF maps will precisely localise elements and XANES spectra should help understand the environment of Zn and Cr, whichwould provide clues on their potential structure. The analysis of several primers, in various states of alteration, will allow understanding the mechanism of thecorrosion inhibition processes and how the protective efficiency is maintained or lost over the years.