5xxx (Al-Mg) and 6xxx (Al-Mg-Si) series alloys are most commonly used in the marine sector as they can guarantee both a good mechanical behaviour and good resistance to corrosion in the marine constructions. In fact, sea water contains high amounts of chlorides that can cause, after short exposure times, the failure of entire metal structures. Since in a boat there is the coexistence of different materials, it is inevitable that some of them must be welded together. Welds between dissimilar materials often require the use of non-traditional techniques, such as the process of Friction Stir Welding (FSW) and explosion welding. In this work, the resistance to corrosion of FSW joints (AA5083/AA6082) and trimetallic explosion welded joints (AA5083/AA1050/structural steel) combining galvanic coupling and immersion tests with microstructural characterization of corroded regions. In particular the focus of the work is on the corrosion behaviour of thermo-mechanically and nugget zones in FSW joints and on the AA1050/steel interface in the trimetallic joints obtained by explosion welding.