The Initiation, Progression, and Stifling of Micro‐Galvanic Corrosion on Cu in Anoxic Aqueous Sulfide Solutions

The growth of Cu 2 S films and the initiation and progression of micro‐galvanic corrosion underneath them were investigated after exposure of Cu to anoxic 0.1 M Cl − solutions containing SH − at concentrations ranging from 10 −5 M to 10 −3 M, for up to 3 years. Post‐exposure surface characterization was performed using scanning electron microscopy (SEM), focused ion beam (FIB) cross‐sectioning, atomic force microscopy (AFM), and surface profilometry. At [SH − ] ≤ 5 × 10 −5 M, a thin and porous Cu 2 S film formed on the Cu surface via general corrosion, favoring surface roughening. Increasing [SH − ] to 5 × 10 −4 or 1 × 10 −3 M resulted in the formation of a compact, crystalline, but non‐uniform Cu 2 S film, under which micro‐galvanic corrosion was observed. A time‐dependent characterization of corrosion damage underlying the Cu 2 S film showed the initiation, propagation, and finally stifling as the film thickened with time. Herein, supported by experimental evidence, a mechanistic pathway for the stifling of the micro‐galvanic corrosion is proposed.