Stainless Steel Surface Structure and Initial Oxidation at Nanometric and Atomic Scales

TL;DR

This study uses scanning tunneling microscopy to explore the atomic-scale surface structure and initial oxidation processes of stainless steel, revealing complex surface features and mechanisms critical for enhancing corrosion resistance.

Contribution

It provides new atomic-scale insights into the initial oxidation mechanisms and surface modifications of stainless steel, advancing understanding of passive film stability.

Findings

Reconstructed atomic lattice with self-organized vacancy lines.

Initial oxidation involves step and vacancy mechanisms leading to Cr-rich oxide formation.

Surface structure influences the stability and composition of the passive oxide film.

Abstract

The durability of passivable metals and alloys is often limited by the stability of the surface oxide film, the passive film, providing self-protection against corrosion in aggressive environments. Improving this stability requires to develop a deeper understanding of the surface structure and initial surface reactivity at the nanometric or atomic scale. In this work we applied scanning tunneling microscopy to unravel the surface structure of a model stainless steel surface in the metallic state and its local modifications induced by initial reaction in dioxygen gas. The results show a rich and complex structure of the oxide-free surface with reconstructed atomic lattice and self-organized lines of surface vacancies at equilibrium. New insight is brought into the mechanisms of initial oxidation at steps and vacancy injection on terraces leading to Cr-rich oxide nuclei and locally Cr-depleted terraces, impacting the subsequent mechanism of chromium enrichment essential to the stability of the surface oxide.