New insights of Auger spectroscopy for the identification of Fe-Si compounds in iron/glass corrosion systems at nanoscale

•Use of Scanning Auger electron microscopy to analyze insulating surfaces.•Creation of a new Si-KLL Auger database of reference spectra obtained on iron-phyllosilicate.•Multi-technical characterization (Auger, TEM) to identify iron-silicate.•Crystallized Fe-rich serpentine detected in glass/iron/claystone system altered at 90°C for 2 years in contact with COx water. In the context of high-level radioactive wastes (HLW) storage, long term alteration of glass and corrosion of metallic containers leads to the formation of sub-micrometric phyllosilicate phases in the iron Corrosion Product Layer (CPL). The nature of these phases, their properties (porosity, electronic, passivation…) and their spatial distribution must be identified to determine their exact role in the iron corrosion process and to efficiently predict the long-term alteration of nuclear wastes package. In this work, the capabilities of localized Auger spectroscopy, combining surface chemical determination and high spatial resolution, to characterize these phyllosilicate phases is presented. In the present context, the main challenge to overcome was the insulating character of the different compounds and samples, presenting a real disadvantage for Auger implementation. A specific experimental protocol had to be developed to enable acquiring exploitable spectra at sufficiently high resolution to obtain identifiable fingerprints. The main Si-KLL Auger transition of different types of phyllosilicates representative of those encountered in the CPL of the glass-iron systems was acquired to determine if different chemical signatures and chemical shifts could be observed in function of the structure of reference phyllosilicates phases. Indeed, the Si-KLL kinetic energy position value of the phyllosilicate increases with the structure according the following order: smectite group