Corrosion of aluminium alloys is frequently observed in the cooling systems of functional vehicles dating from 1920 to 1940 in the Musée National de l'Automobile in Mulhouse, France. This paper shows how DiscoveryMat, a freeware analytical tool, has been successfully used for the in situ analysis of the materials concerned. The tool is based on the monitoring of the electrochemical behavior of metals in different test solutions and relies on a database to propose possible alloy compositions. The analysis of a corpus of detached parts representative of this problem has made it possible to enrich the database, thus enabling the precise identification of the problematic aluminium alloys in real conditions directly on the vehicles. The results of these analyses showed that the corroded parts are all made of AI-Cu(-Si) alloys, whereas the most recent and stable parts are made of AI-Si alloys.