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Chemical durability of metallic materials

The SIR group is responsible for wet and dry corrosion activities at SIMaP, from both the fundamental and applied points of view.

 

 Work on wet corrosion (B. Baroux, B. Malki, R. Nogueira, M. Reboul) has led to the development of three well-identified aspects: 

  • the influence of metallurgical parameters on localised corrosion of iron-based or aluminium-based passivable alloys,
  • modelling and simulation of localised corrosion,
  • the microscopic behaviour of interfaces.

     With regard to the first aspect, the most recent results throw light on changes in the semi-conducting properties of passive films depending on the industrial surface state of stainless steels (in collaboration with Arcelor Mittal - postdoc 2007). Work has also focused on the influence of microstructure on the exfoliation corrosion of aluminium alloys in the framework of the ANR SICORAL, work that is being promoted within SIMaP by both the SIR and PM groups. Significant progress has been made with regard to the second aspect by taking greater account of the chemical composition of the solution in pitting and by using several different methods (Monte-Carlo, PLCs). This work has made particular progress within the Reactivity and Engineering of Metallic Surfaces CNRS research group, for which we were largely responsible and which ended recently. Lastly, we developed computer-based simulations of the microscopic behaviour of dissolving metal-electrolyte interfaces followed by experimental studies that confirm the existence of a behaviour pattern that has been postulated theoretically but never previously reported, associated with an abnormal faceted morphology of the interface of a dissolving polycrystalline metal.

 

      Research in the field of high-temperature oxidation and corrosion (A. Galerie, Y. Wouters) has received Carnot "Materials for energies of the future" certification. The industrial and social challenge is to make sure that systems working at high temperature have maximum durability, which is synonymous with economic savings, coupled with prospects of sustainable development by optimising recycling times. The scientific goal is to gain a better understanding of the parameters and mechanisms that condition such durability. Our work has concerned thin FeCrAl alloy strip used for catalytic converters (collaboration with ENP Algiers, thesis by R. Chegroune), zirconium alloys (collaboration with CEA-Saclay), Ni-based alloys (collaboration with AREVA NP), the metal interconnectors of SOFCs (Franco-Thai programme and support from Arcelor Mittal). Research on SOFC interconnectors has expanded through the signing of two successive Franco-Thai partnership agreements (PHC) on this topic, which highlight the behaviour of interconnectors in the presence of gas biofuels on the anode side. A jointly supervised doctoral thesis (P. Promdirek) has been in progress since September 2007. It is also worth noting that the group is a partner in the ANR ICARE (InterConnecteurs en Alliages Revêtus - Coated Alloy Interconnectors) project that is looking at HTE (high-temperature electrolysis) electrodes which have more or less the same problems to those with SOFCs.

 

     From the fundamental standpoint, we have demonstrated experimentally beyond any doubt (G. Bamba et al., Scripta Mater. 2007) that the growth direction of thermal chromium oxide on stainless steel is reversed owing to the mobile hydroxylated chemical species in Cr2O3. We have also become a member of the new CNRS "EVAPE" research group concerned with the "steam" aspects of high-temperature oxidation phenomena. Within this community, we are responsible for carrying out detailed mechanistic studies.

 
 
 Corrosion : experiments and simulation
 
   
 
 Simulation of intergranular dissolution of aluminium alloys  16O/18O  SIMS profiles in two  Cr2O3 scales grown on stainless steel at 850°C in oxygen (top), in water vapour (bottom) 
 

Date of update January 7, 2016

Univ. Grenoble Alpes