Atomistic insights into chloride-induced depassivation mechanisms of protective Cu2O films in marine environments

Abstract

Copper (Cu) is widely utilized in industrial and marine engineering due to its exceptional thermal and electrical conductivity . In alkaline environments , a passivation layer, primarily composed of Cu 2 O, forms on copper surfaces, effectively inhibiting corrosion. However, in marine environments, this protective film becomes vulnerable to attack by aggressive Cl - ions, leading to film detachment. Several mechanisms have been proposed to explain the depassivation of Cu 2 O, including stress-induced fracture, local thinning, and void-induced collapse mechanisms. Nevertheless, the precise atomic-scale processes at the Cu 2 O/seawater interface remain poorly understood, leaving the exact mechanism by which Cl - promotes Cu 2 O depassivation debated. To elucidate the atomic-scale mechanism of Cl - -induced Cu 2 O corrosion, this study employs advanced computational techniques: ab initio thermodynamics, machine learning potential-based molecular dynamics , and constrained molecular dynamics . Our results reveal that under marine conditions, Cl - undergoes extensive chemisorption on the Cu 2 O(111) surface. This adsorption markedly reduces the energy barrier for lattice copper dissolution. Furthermore, we demonstrate that the formation rate of surface Cu + vacancies far exceeds their longitudinal diffusion rate into the bulk. Based on this kinetic disparity, we propose that Cl - -mediated Cu 2 O depassivation primarily proceeds via the local thinning mechanism. Overall, this work clarifies the breakdown mechanism of passive films on copper and provides a critical theoretical basis for designing corrosion-resistant Cu-based alloys used in marine environments.

Topics & Concepts