Effect of pH on hydrogen pick-up and corrosion in zircaloy-4
<p>Thermal Desorption Spectroscopy (TDS) has been used to investigate the hydrogen pick-up behaviour in different samples of Zircaloy-4. This includes as-received, cold rolled, hydrogen charged, and autoclave-oxidised in pure water and at an elevated pH (with 50% deuterated water) compared to...
| Main Authors: | , , , |
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| Format: | Conference item |
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Springer
2017
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| _version_ | 1797078622610128896 |
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| author | Sayers, J Ortner, S Li, K Lozano-Perez, S |
| author_facet | Sayers, J Ortner, S Li, K Lozano-Perez, S |
| author_sort | Sayers, J |
| collection | OXFORD |
| description | <p>Thermal Desorption Spectroscopy (TDS) has been used to investigate the hydrogen pick-up behaviour in different samples of Zircaloy-4. This includes as-received, cold rolled, hydrogen charged, and autoclave-oxidised in pure water and at an elevated pH (with 50% deuterated water) compared to commercial reactors. A characteristic desorption peak for hydrogen has been found at ~650°C, which is theorised to come from hydrides1. Cold rolled samples show the same general shape spectrum as the as-received samples, with more hydrogen detected per unit volume of sample. This suggests more hydrogen is in trapping sites or outward diffusion paths are facilitated by dislocations, since no more hydrogen has been added. The peak broadens towards higher temperature, which indicates that additional dislocations could provide trapping sites with a slightly higher energy than the average in the as-received samples. The hydrogen charged samples form a hydride rim, which contains much more hydrogen than the as-received samples. The peak broadens but on average does not shift.</p> <br/> <p>The surface oxide, when present, layer acts as a barrier to the desorption of hydrogen, until the temperature rises enough for the oxygen to migrate into the bulk. The oxide itself only contains a small amount of hydrogen, as is evidenced when the oxide layer is removed, whereupon the desorption peak returns to the characteristic shape seen in as-received samples.</p> <br/> <p>Samples oxidised in pure water exhibit a slightly higher oxidation rate, and pass through kinetic transition much earlier than samples exposed to an elevated pH. Before transition, pH has little effect on the hydrogen pick-up. After transition, the hydrogen pick-up is much higher in pure water, which implies that the H+ concentration in the environment affects hydrogen pickup at this stage. The elevated pH samples showed peaks for D-H and D2, which follow the H2 peaks. The hydrogen content in these samples increases at around 70% of the time to the first transition. This may correlate with development of through-thickness percolation paths, which could lead to the pH inside cracks being modified to a lower value, increasing the availability of H+ ions.</p> |
| first_indexed | 2024-03-07T00:34:24Z |
| format | Conference item |
| id | oxford-uuid:80e4943d-b46c-468d-8a1a-639b2c42d3f9 |
| institution | University of Oxford |
| last_indexed | 2024-03-07T00:34:24Z |
| publishDate | 2017 |
| publisher | Springer |
| record_format | dspace |
| spelling | oxford-uuid:80e4943d-b46c-468d-8a1a-639b2c42d3f92022-03-26T21:26:33ZEffect of pH on hydrogen pick-up and corrosion in zircaloy-4Conference itemhttp://purl.org/coar/resource_type/c_5794uuid:80e4943d-b46c-468d-8a1a-639b2c42d3f9Symplectic Elements at OxfordSpringer2017Sayers, JOrtner, SLi, KLozano-Perez, S<p>Thermal Desorption Spectroscopy (TDS) has been used to investigate the hydrogen pick-up behaviour in different samples of Zircaloy-4. This includes as-received, cold rolled, hydrogen charged, and autoclave-oxidised in pure water and at an elevated pH (with 50% deuterated water) compared to commercial reactors. A characteristic desorption peak for hydrogen has been found at ~650°C, which is theorised to come from hydrides1. Cold rolled samples show the same general shape spectrum as the as-received samples, with more hydrogen detected per unit volume of sample. This suggests more hydrogen is in trapping sites or outward diffusion paths are facilitated by dislocations, since no more hydrogen has been added. The peak broadens towards higher temperature, which indicates that additional dislocations could provide trapping sites with a slightly higher energy than the average in the as-received samples. The hydrogen charged samples form a hydride rim, which contains much more hydrogen than the as-received samples. The peak broadens but on average does not shift.</p> <br/> <p>The surface oxide, when present, layer acts as a barrier to the desorption of hydrogen, until the temperature rises enough for the oxygen to migrate into the bulk. The oxide itself only contains a small amount of hydrogen, as is evidenced when the oxide layer is removed, whereupon the desorption peak returns to the characteristic shape seen in as-received samples.</p> <br/> <p>Samples oxidised in pure water exhibit a slightly higher oxidation rate, and pass through kinetic transition much earlier than samples exposed to an elevated pH. Before transition, pH has little effect on the hydrogen pick-up. After transition, the hydrogen pick-up is much higher in pure water, which implies that the H+ concentration in the environment affects hydrogen pickup at this stage. The elevated pH samples showed peaks for D-H and D2, which follow the H2 peaks. The hydrogen content in these samples increases at around 70% of the time to the first transition. This may correlate with development of through-thickness percolation paths, which could lead to the pH inside cracks being modified to a lower value, increasing the availability of H+ ions.</p> |
| spellingShingle | Sayers, J Ortner, S Li, K Lozano-Perez, S Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title | Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title_full | Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title_fullStr | Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title_full_unstemmed | Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title_short | Effect of pH on hydrogen pick-up and corrosion in zircaloy-4 |
| title_sort | effect of ph on hydrogen pick up and corrosion in zircaloy 4 |
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