Evaluating the Corrosion Behaviour of Copper during Deliquescent Drying/Wetting Cycles in Humid Air
Bibliographic record
Abstract
Copper and its alloys are highly valued for their moldability, heat/electricity conduction, and corrosion resistance, making them widely used in various industrial applications. One potential application of copper is as the corrosion barrier for used nuclear fuel containers (UFCs) within a deep geological repository (DGR) in Canada, Sweden and Finland. The UFC's copper surface will be exposed to different conditions in the evolving DGR environment, which will transition from warm, dry, and oxic to cool, wet, and anoxic conditions. Deliquescence is a known process in forming the initial corrosive solutions/droplets that may occur as a result of adsorption of moisture by salt particles at the UFC surface during the unsaturated phase in a DGR. The duration over which the surface will remain wet under oxic condition will impact the extent of copper corrosion. To investigate this phenomenon, the quartz crystal microbalance (QCM) technique was used. The QCM consists of a quartz plate, covered by gold electrodes on both sides onto which a layer of copper is deposited using e-beam deposition. In this technique, the change in the resonance frequency of a vibrating quartz crystal is linearly proportional to the change in mass on the crystal's surface (Δm) under certain conditions with a sensitivity in the nanogram range. In this study this effect was used to monitor the adsorption and evaporation of water, the salt depletion, and to quantify the extent of atmospheric corrosion on copper surfaces. To systematically study the atmospheric corrosion of copper surfaces, controlled amounts of different salts (NaCl, CaCl2, and MgCl2) were loaded onto copper-coated QCM crystals using an inkjet printer, and then corrosion tests were performed at different relative humidity (RH) values depending on the deliquescence relative humidity (DRH) of each salt at 75 °C. Results revealed that for NaCl, the surface remained continuously wet above its DRH (75% RH). However, for CaCl2, the time of wetness was relatively short post-deliquescence. Corrosion continued beyond this wet period, eventually depleting all the salt and forming non-deliquescent products. Higher RH levels prolonged the wetness period and accelerated the salt depletion, leading to a stabilized corrosion rate comparable to that of bare copper under similar conditions. Similarly for MgCl2, the time of wetness was also limited, and higher RH extended the wetness duration. Interestingly, corrosion rates differed from those observed with CaCl2. Surface analysis techniques, including focused ion beam (FIB) cutting and energy dispersive X-ray spectroscopy (EDS), were used to examine the composition and structure of corrosion films for CaCl2, providing insights into the underlying corrosion mechanisms. Further analyses are ongoing for both CaCl2 and MgCl2 to better understand their distinct corrosion behaviours.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".