This proposal aims at better understanding intergranular corrosion in molten salts. Molten alkali-alkaline earth chloride salts are promising heat transfer fluids for solar power plants and future molten salt reactors, where they could also act as fuel components. Their use raises important challenges related to the selection of structural materials in contact with molten salts. Indeed, Fe- and Ni-based alloys are corroded in contact with molten salts and often display intergranular corrosion. To solve this urgent concern, one needs to understand corrosion mechanisms and kinetics, especially the evolution of grain boundaries (GB). To do so, we want to monitor corrosion in situ by using 3D X-ray diffraction (3DXRD) and tomography (PCT). These experiments will be coupled with ex situ 3D diffraction contrast tomography (DCT) and scanning XRD (SXRD) before and after corrosion to access higher spatial resolution and retrieve a multiscale overview of corrosion in molten salts.