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Investigation of chloride-induced depassivation of iron in alkaline media by reactive force field molecular dynamics

Evidence and attribution

Authority of statements

This slug registers a second corpus path (papers/ReaxFF_others/DorMohammedi_NatureMatDeg_2019_FeCl.pdf) for the same npj Materials Degradation article as 2019dormohammadi-npj-material-investigation-chloride-induced. Full protocol locators and evidence anchors follow the canonical page.

Summary

Chloride attack on passive iron in alkaline media matters for reinforced concrete and corrosion-resistant alloys, yet atomistic mechanisms must reconcile thin-film chemistry with macroscopic polarization data. npj Materials Degradation emphasizes interface science accessible to materials and civil engineers, so the simulation cells deliberately isolate Fe electrochemistry from cement pore solution complexity while still capturing chloride-catalyzed vacancy physics argued to be transferable across substrates. DorMohammadi, Pang, Murkute, Arnadottir, and Isgor combine ReaxFF MD with electrochemical measurements and XPS on Fe electrodes in pH ~13.5 NaOH with chloride additions. The npj Materials Degradation article argues chloride accelerates iron-vacancy creation and migration within the oxide, promoting local acidification and Fe dissolution without requiring classical film penetration as the sole mechanism. This wiki slug mirrors [[2019dormohammadi-npj-material-investigation-chloride-induced]] but records a second PDF path under papers/ReaxFF_others/ with distinct SHA-256 provenance.

Methods

This slug is a duplicate corpus path for the same npj Materials Degradation article as [[2019dormohammadi-npj-material-investigation-chloride-induced]].

Experiments + spectroscopy. Follow the canonical page for electrochemical + XPS specimen preparation and measurement narratives.

Reactive MD protocol (same article). [[2019dormohammadi-npj-material-investigation-chloride-induced]] summarizes the LAMMPS/ReaxFF workflow as published: 300 K, NVT with Nosé–Hoover thermostat, 0.1 fs timestep, COM constraint, Fe/oxide/electrolyte supercell with 3D periodic boundary conditions (PBC) (see canonical page for atom counts and slab/vacuum dimensions), energy minimization plus equilibration/production stages out to multi-nanosecond totals discussed in the Results (PDF). Hydrostatic pressure: N/A — NVT cell rather than NPT servocontrol in the excerpted protocol.

Electric fields / enhanced sampling. N/A — not summarized as a distinct applied-field MD workflow on this duplicate-ingest note (see canonical page + PDF for any field-coupling approximations discussed by the authors).

Findings

Depassivation follows a multi-step sequence: local pH drops at oxide defects, Fe dissolves, and Fe vacancies accumulate inside the passive layer; chloride catalyzes vacancy nucleation and hops toward the metal, amplifying breakdown relative to chloride-free alkaline controls. XPS and polarization curves support the qualitative current and composition trends inferred from MD. For figure numbers and SI tables, use the canonical page unless this duplicate PDF is required for manifest auditing. The npj Materials Degradation framing ties atomistic vacancy physics to rebar corrosion contexts where alkaline pore solutions coexist with chloride ingress, even though the simulations use model Fe electrodes rather than cement paste microstructures.

Limitations

Simplified substrates vs industrial steels; MD time and length scales; duplicate PDF only changes provenance, not scientific limits.

Relevance to group

ReaxFF application to corrosion and passivation in alkaline environments; this file preserves hash-disambiguated ingest.

Citations and evidence anchors

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