Electrochemical Properties of X-65 Pipeline Steel in Dilute HCO3−/CO32− Solutions
Bibliographic record
Abstract
Abstract In this study, the electrochemical behaviour of X65 pipeline steel was investigated in three dilute HCO3− solutions, i.e., 10 mM, 20 mM, and 50 mM, purged with 5% CO2/N2 or 100% CO2 to achieve the typical pH of the trapped water under a disbonded shielding coating, i.e., pH 5.5 to 7.5. The measurements of corrosion potential (Ecorr) showed that the free corrosion process of X65 carbon steel in dilute HCO3− solutions involves Fe – 2e− → Fe2+ as the anodic reaction coupled with H+ + e− → ½H2 as the cathodic reaction. The investigation of the anodic polarization behaviour of X65 carbon steel in dilution HCO3− solutions purged with N2 + 5% CO2 confirmed that the anodic reaction, Fe – 2e− → Fe2+, was under mixed diffusion-electrochemical control. The anodic Tafel slope displayed a value of ~60 mV/decade in the 10mM HCO3− solution. As the HCO3− concentration was increased from 10 mM to 50 mM, the anodic Tafel slope constantly increased from ~ 60 to ~ 90 mV/decade. Cathodic polarization curves displayed a current-peak region at the low cathodic polarization range, -0.95 V to -0.75 V, and a typical Tafel region at potentials beyond -0.95 V. The current-peak within the low cathodic polarization range could be due to the catalyzing effect of the partially oxidized surface on the hydrogen evolution reaction (HER), and this catalyzing effect was enhanced by increasing HCO3− concentration or/and pH. A high cathodic Tafel slope, i.e, ~ 200 mV/decade, was observed for the HER at E < -0.95 V.
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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 | 0.000 |
| 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 | 0.000 |
| 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".