The atmospheric corrosion of 304L and 316L stainless steels under conditions relevant to the interim storage of intermediate level nuclear waste

The atmospheric corrosion of 304L and 3 16L austenitic stainless steels was investigated in conditions relevant to the storage of intermediate level nuclear waste (I L W). Thin electrolyte films were created via automated droplet deposition, allowing multiple tests to be conducted in parallel. In-situ monitoring of droplet arrays on stainless steel samples was conducted with the use of a flat-bed document scanner, allowing large-scale, automated monitoring of corrosion processes. The initiation time for individual corrosion processes was established, showing that corrosion was slower to initiate under less aggressive conditions, and allowing 'true corrosion site lifetimes to be recorded, and compared with their depths. The presence of precipitated species within an electrolyte film was shown to affect the corrosion processes within that film. Both NaCl precipitates and glass shards acted as barriers to ion transport. This affected both the propagation of corrosion, and the electrochemical potential within the droplets; a higher precipitate content decreased the average corrosion depth and the extent of corrosion. The presence of nitrate and sulphate salts, both known corrosion inhibitors in full- immersion conditions, was shown to inhibit atmospheric corrosion when the inhibitor:chloride ratio was above a certain value. This was independent of the absolute amounts of salts, but dependent on the exposure humidity of the test