In the railway sector, aluminium is becoming the preferred alloy for the car-body shell construction. Welding aluminium alloys for structural applications has to comply to specific Standards that allow to guarantee the proper design, the manufacturing and the in-service reliability. In the railway market, welding is often defined as Special Process. Indeed, even if the process parameters are controlled, the conformance of the resultant weld can be checked only with destructive tests. Although some destructive tests can be done in the welding validation phase, in the past years, the non-destructive evaluation of these structures has assumed a crucial role both at a manufacturing and at in-service levels.