Aluminum-based PVD protective coatings as corrosion barrier in nuclear plants

Lead alloys are attractive candidates as coolants for future generation nuclear reactors (for both fission fast reactors and fusion plants). However, one of the concerns with the use of liquid metals is their compatibility with the containment structure since they are very corrosive for structural steels. To reduce the corrosion phenomenon, surface coatings may be applied for an enhanced protection against the lead alloys. In this study, T91 steel samples were coated by using two different PVD techniques with two different aluminum-based materials classes. Aluminum Oxide coatings (Al-O) were deposited by Radio Frequency Magnetron Sputtering (RF-MS) and Aluminum Titanium Nitride coatings (AlTiN) were deposited by High Impulse Magnetron Sputtering (HiPIMS). Corrosion tests in stagnant lead were performed at 550°C for 1200 h. Cross-sectional SEM and EDX analysis after molten Pb test revealed no signs of corrosion for both coatings typologies. Since in convective molten metal also mechanical properties such as adhesion and wear resistance will be severely stressed, the tribological performance of the films before and after corrosion treatment have been extensively characterized.