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This work analysed the effect of chloride deposition on the susceptibility to atmospherically induced stress corrosion cracking (AISCC) of stainless steel type AISI 316L used to manufacture containers for radioactive intermediate level waste in the UK. Using U-bend specimens contaminated with MgCl 2 , a threshold deposition for AISCC occurrence has been found above chloride contamination levels of 10 and 25 mg cm 22 at 50 and 30uC respectively at the equilibrium relative humidity (RH) of the contaminant salt (,30%RH). Higher contamination levels were required to produce cracking at 60%RH. Based on crack depth data and contaminated area characterisation, it was found that susceptibility to AISCC is affected by the liquid film volume, thickness and continuity.

In situ synchrotron radiography has been used to observe the evolution of two-dimensional pits growing in stainless steel foils under electrochemical control in chloride solutions. A method for extracting the key kinetic parameters from radiographs is under development to provide data for validating and calibrating a two-dimensional finite element model previously developed by Laycock and White. The local current density along the boundary of a pit is directly measured from the radiographs. Then, the local metal ion concentration and potential drop inside the pit cavity are backcalculated using transport equations and the requirement to maintain charge neutrality, giving the relationship between current density, solution composition and interfacial potential. Preliminary comparisons show qualitative correlation between the model and extracted data; quantitative comparison is under way.

Two forms of high resolution X-ray tomographic experiments (i.e. synchrotron based X-ray microtomography and desktop microfocus computed X-ray tomography) are demonstrated in the present paper to illustrate the wide application of these techniques for qualitative and quantitative studies of localised corrosion and environmentally assisted cracking. Specifically, synchrotron based X-ray tomography was used to investigate the localised corrosion morphology within aluminium specimens when exposed in situ to a chloride environment while microfocus computed X-ray tomography was used to investigate the morphology and quantify the transition from localised corrosion to stress corrosion cracking in steel specimens exposed ex situ to a simulated corrosive condensate environment.