Corrosion behavior of martensitic/ferritic oxide dispersed strengthened steels in nitric media
- PDF / 304,040 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 111 Downloads / 207 Views
Corrosion behavior of martensitic/ferritic oxide dispersed strengthened steels in nitric media Benoit Gwinner1, Martin Auroy1, Dominique Mas1 and Audrey Saint-Jevin1 CEA, DEN, DPC, SCCME, Laboratoire d’Etude de la Corrosion Non Aqueuse, F-91191 Gifsur-Yvette, France. 1
ABSTRACT The corrosion behavior of three martensitic/ferritic oxide dispersed strengthened (ODS) steels with different chromium contents (respectively 9, 14 and 18wt %) has been studied in hot and concentrated nitric acid. Immersion and electrochemical tests have been carried out in different experimental conditions (temperature and nitric acid concentration). In each case, the corrosion kinetics has been characterized by mass loss measurement of samples (immersion tests) and the electrochemical behavior by linear sweep voltammetry techniques. The dependency of the corrosion rate with the chromium content in the steel, the nitric acid concentration and the temperature, has been quantitatively established and qualitatively discussed. INTRODUCTION The martensitic/ferritic oxide dispersed strengthened (ODS) steels are promising materials for the fuel cladding of the sodium cooled fast nuclear reactors (SFR). Some studies are currently in progress at CEA to elaborate these steels and demonstrate their good properties for this application (mechanical resistance, ageing behavior …). Among them a dedicated research program has been launched to evaluate the impact of the corrosion of the cladding on the fuel reprocessing PUREX process. During the fuel dissolution step by nitric acid, the cladding can indeed be corroded and the corrosion products (mainly iron and chromium) can be released in the dissolution medium. These releases have to be limited for the well working of the process. Thus the corrosion behavior of different potential cladding materials (steels) in nitric acid is studied. The main aim of this work is to quantify the corrosion rate of these different steels in a large range of dissolution conditions (nitric acid concentration and temperature). These results will be helpful for the future industrial decision concerning the choice of the best cladding material and the optimum fuel dissolution conditions. EXPERIMENT Three steels elaborated at CEA are studied. Their crystalline structure and chemical composition are given in table I. Table I. Crystalline structure and chemical composition of the steels (wt %) Steel 9Cr-1W-Ti ODS 14Cr-1W-Ti ODS 18Cr-1W-Ti ODS
Structure Martensitic Ferritic Ferrtic
Fe Bal. Bal. Bal.
Cr 9 14 18
9
W 1 1 1
Ti 0.3 0.3 0.3
Y 0.3 0.3 0.4
Si 0.2 0.3 0.3
Ni 0.4 0.2 0.2
Mn 0.3 0.3 0.3
The corrosion experiments consist in immersion and electrochemical tests on these steels in nitric media. The immersion tests are performed with parallelepiped samples of the steels (10x30x1mm) immersed in nitric acid at different temperatures (70°C-90°C-boiling point) and at different concentrations (3-6-9 mol/L). The ratio S/V (the steel area on the volume of nitric acid) and the test duration are identical for each test (S/V = 4.
Data Loading...
