Significance of Corrosion Phenomena for Magnets of Accelerators, Fusion and High Energy Physics Experiments

Although superconducting accelerator and fusion magnets operate at cryogenic temperature and in most cryogenic applications corrosion is not an issue, it is essential to avoid corrosion phenomena that may occur during production and fabrication of parts and components of magnet systems, or during their installation, assembly or maintenance. A delayed leak or a structural failure that would arise in operation due to onset of corrosion phenomena at an earlier stage could lead to grave consequences due to many such components becoming embedded and virtually unrepairable. Therefore, corrosion prevention is of paramount importance in all the phases of a project involving superconducting or even normal conducting magnets and their vacuum systems, including during storage of components or assemblies before their final commissioning and operation, in order to minimise the associated risks and guarantee their reliability over time. The return from decades of experience in assessing and investigating magnet components and ancillaries, and in analysing their failures is presented, showing the relevance and variety of corrosion phenomena that may affect magnet systems of accelerators, high energy physics experiments and fusion devices and their ancillaries. Through the examples and the failure analyses provided, the paper discusses the most relevant corrosion mechanisms, their prevention and applicable remediation actions, that have been of paramount importance for a reliable operation of the magnet systems.