Corrosion Mechanism of Nickel-Containing Stainless Steels in Concentrated Aqueous Solutions of Sulfuric Acid
Bibliographic record
Abstract
The present investigation was undertaken to interpret the spontaneous oscillating activation-passivation corrosion behavior of nickel-containing stainless steel (SS) in concentrated sulfuric acid (H2SO4) solutions using a galvanic passivation model. This was attempted by modeling the oscillating sequence of UNS S30403 in 93.5 wt% H2SO4 at 60°C using a nickel sulfide/nickel (NiS/Ni)-UNS S43000 (a nickel-free SS with similar chromium content to UNS S30403) galvanic couple. Electrochemical measurements showed that galvanic passivation of UNS S43000 is possible when connected to NiS. The behavior is due to the ability of NiS to depolarize the reduction of undissociated H2SO4 molecules to a level that stabilizes the passive film. The model system was found to reproduce the major process involved in the oscillating sequence, namely passivation induction, passivation, and activation. Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) analyses on the surface of UNS S30403 provided evidence to support the model, namely the presence of a chromium-rich oxide-hydroxide film and NiS after spontaneous passivation. The major processes involved in the oscillating sequence are considered to relate to the manner in which NiS grows and subsequently dissolves during corrosion. The findings have meaningful implications regarding the development of more corrosion-resistant SS.
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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) | 0.000 | 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".