Beyond Breakaway Corrosion: Secondary Corrosion Protection of Iron-based Alloys
In order to address, and systematically investigate the corrosion behaviour after breakaway, this thesis introduces the concept of primary and secondary corrosion protection for the oxide scales formed before and after breakaway, respectively. The concept is considered to be important for the development and selection of materials to be used in applications where the breakaway event cannot be prevented, e.g. in biomass- and waste-fired boilers, as well as for the development of lifetime predictive modelling tools for corrosion. A systematic study of the secondary corrosion regime is performed by well-controlled breakdown of the primary corrosion protection of Fe-based model alloys. The resulting oxide scales are subjected to detailed microstructural investigation to study the general aspects of the secondary corrosion protection and how its properties and microstructure changes e.g. by altered alloy composition.
The results show that the oxide scales formed after breakaway exhibit similar microstructural features on all the exposed FeCr(Ni/Al) model alloys and that the growth of the secondary corrosion protection is mainly diffusion-controlled. Thus, lifetime predictive tools using diffusion-based simulations, such as DICTRA, could be developed to predict corrosion both before and after breakaway. However, it is also shown that corrosive species (e.g. KCl) may affect the mechanical integrity of the oxide scale, resulting in growth processes that requires other types of models. Furthermore, the results show that the growth rate in the secondary corrosion regime may be influenced by the alloy composition, for example by adding Ni or a combination of Al/Cr. This behaviour is not directly connected to how well the primary corrosion protection withstands the exposure environment (i.e. the incubation time to breakaway). Thus, these findings indicate that research on the secondary corrosion protection has a large potential to improve the selection and development of alloys for use in corrosive environments, such as biomass- and waste-fired boilers.
High temperature corrosion
Chalmers, Kemi och kemiteknik, Energi och material, Oorganisk miljökemi
Oxidation of Fe-2.25Cr-1Mo in presence of KCl(s) at 400 °C – Crack formation and its influence on oxidation kinetics
Corrosion Science,; Vol. 163(2020)
Artikel i vetenskaplig tidskrift
A. Persdotter, J. Eklund, J. Liske, T. Jonsson, Beyond Breakaway Corrosion - Influence of Chromium, Nickel and Aluminium on Corrosion of Iron-based Alloys at 600 °C. Accepted in Corrosion science 2020.
Metallurgi och metalliska material
Chalmers tekniska högskola
Seminar room 6055, Kemigården 4, Campus Johanneberg, Chalmers University of technology
Opponent: Dr. Javier Pirón, Vallourec Research Center Germany (VRCG), Düsseldorf, Germany.