The proof of concept of the effectiveness of sol-gel coatings doped with carboxylic acid for the protection of copper-bearing heritage metals was demonstrated in a first PhD-thesis conducted within a NIMBE LAPA/LEDNA collaboration. In order to optimise the formulation of this coating on metals with a Corrosion Product Layer (CPL) of several tens of micrometres thickness that needs to be preserved, it is necessary to develop an in-depth study of the physico-chemical mechanisms of the protection. In this new thesis project, a multi-technique and multi-scale characterisation methodology will be implemented on old CPC samples as well as on model CPC samples. On the one hand, the formulation parameters (TMOS and/or TEOS precursors) will be adjusted to favour brush or spray application. On the other hand, the protection mechanisms will be studied through electrochemical measurements as well as through re-corrosion experiments in marked media (D2O/18O2, KBr under aggressive immersed conditions). The analytical protocol will be based on analyses at the global scale (viscosity, BET, mercury porosimetry, ATG, DRX), at the micrometric scale (SEM-EDS, Raman spectrometry) as well as at the nanometric scale (TEM on FIB slides) in order to understand the systems obtained during the treatments.