LOCALISED CORROSION OF STAINLESS STEELS 316L AND 2205 IN SYNTHETIC BENTONITE PORE WATER AND BENTONITE SLURRY

One concept for Czech canister construction for deep geological repository considers stainless steel as an inner case material. Corrosion resistance to localised (pitting/crevice) corrosion and stress corrosion cracking of austenitic stainless steel 316L and duplex steel 2205 was studied. The environment was synthetic bentonite pore water (SBPOW) of domestic bentonite BaM, or a slurry of bentonite in SBPOW. Tests were carried out between 40 °C and 90 °C under anaerobic conditions of a nitrogen atmosphere. The following methods were used for evaluation: potentiostatic tests at oxidation-reduction potential of the environment, long-term exposure tests in SBPOW and slurry, slow strain rate tensile test (SSRT), exposure test of U-bends, and optical microscopy. Results showed no susceptibility of either material to stress corrosion cracking. No localised corrosion was observed up to 70 °C. There was no localised attack observed in SBPOW at 90 °C, but there was localised corrosion detected in the bentonite slurry. Forced breakdown of the passive layer during SSRT, and artificial crevices (O-rings), showed no effect on localised corrosion propagation. The detrimental effect was probably a result of the adsorption ability of the bentonite particles, which allowed breakdown of passive layer and disabled repassivation of metastable pits.

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LOCALISED CORROSION OF STAINLESS STEELS 316L AND 2205 IN SYNTHETIC BENTONITE PORE WATER AND BENTONITE SLURRY

Acta Metallurgica Slovaca ◽

10.12776/ams.v1i1.1197 ◽

2019 ◽

Vol 25 (1) ◽

pp. 24

Author(s):

Jan Stoulil ◽

Liudmila Pavlova ◽

Milan Kouřil

Keyword(s):

Stainless Steel ◽

Stress Corrosion ◽

Pore Water ◽

Stress Corrosion Cracking ◽

Passive Layer ◽

Nitrogen Atmosphere ◽

Corrosion Cracking ◽

Stainless Steel 316L ◽

Exposure Test ◽

Bentonite Slurry

<p class="AMSmaintext">One concept for Czech canister construction for deep geological repository considers stainless steel as an inner case material. Corrosion resistance to localised (pitting/crevice) corrosion and stress corrosion cracking of austenitic stainless steel 316L and duplex steel 2205 was studied. The environment was synthetic bentonite pore water (SBPOW) of domestic bentonite BaM, or a slurry of bentonite in SBPOW. Tests were carried out between 40 °C and 90 °C under anaerobic conditions of a nitrogen atmosphere. The following methods were used for evaluation: potentiostatic tests at oxidation-reduction potential of the environment, long-term exposure tests in SBPOW and slurry, slow strain rate tensile test (SSRT), exposure test of U-bends, and optical microscopy. Results showed no susceptibility of either material to stress corrosion cracking. No localised corrosion was observed up to 70 °C. There was no localised attack observed in SBPOW at 90 °C, but there was localised corrosion detected in the bentonite slurry. Forced breakdown of the passive layer during SSRT, and artificial crevices (O-rings), showed no effect on localised corrosion propagation. The detrimental effect was probably a result of the adsorption ability of the bentonite particles, which allowed breakdown of passive layer and disabled repassivation of metastable pits.</p>

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Corrosion and Stress Corrosion Cracking Susceptibility of Type 347H Stainless Steel in Supercritical Water

CORROSION ◽

10.5006/2459 ◽

2017 ◽

Vol 74 (1) ◽

pp. 83-95 ◽

Cited By ~ 4

Author(s):

Xianglong Guo ◽

Wenhua Gao ◽

Kai Chen ◽

Zhao Shen ◽

Lefu Zhang

Keyword(s):

Stainless Steel ◽

Stress Corrosion ◽

Oxygen Content ◽

Supercritical Water ◽

Stress Corrosion Cracking ◽

Corrosion Cracking ◽

General Corrosion ◽

Scattered Electron ◽

Intergranular Cracking ◽

Exposure Test

The corrosion resistance and stress corrosion cracking (SCC) susceptibility of Type 347H stainless steel (SS) in supercritical water (SCW) were investigated. The general corrosion behavior was investigated by exposure test and the specimens after testing were characterized utilizing scanning electron microscopy (SEM), Auger and x-ray diffraction analysis, optical microscopy, and energy dispersive spectroscopy (EDS). The results show that with the increase of testing temperature, the corrosion rate of the materials is greatly enhanced. The corrosion process is analyzed and the formation of oxide islands on the surface of the corroded sample is attributed to the higher diffusion rate of Cr along the grain boundary. The effects of temperature and dissolved oxygen on SCC susceptibility were investigated by slow strain rate tensile test. The fractographs were characterized by SEM and the cross-section morphologies were characterized with back-scattered electron imaging, SEM, and EDS. The results indicate that, as temperature is increased, the tensile strength and strain of materials is greatly reduced, while the oxygen content in SCW has a limited effect on the mechanical properties. Intergranular cracking and ductile fracture are the main fracture modes for Type 347H SS tested in SCW, independent of temperature and oxygen content. The implications of the results to the mechanisms of SCC are discussed.

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