Topographical and statistical studies of the corrosion damage underneath a sulfide film formed on a Cu surface

Damage to Cu corroded in sulfide-containing solutions was investigated using scanning electron microscopy and surface profilometry. For dilute sulfide solutions (≤ 5 × 10 −5 M), a thin, porous film was formed, and general corrosion to a depth of < 1 μm observed. At a higher concentration (5 × 10 −4 M), a compact film was formed and micro-galvanic corrosion observed. With increasing exposure time at higher concentration, the extent of micro-galvanic corrosion decreased in favor of general corrosion, as the aspect ratio of the locally corroded sites increased. This indicates that micro-galvanic corrosion will eventually be stifled and only rough general corrosion observed. • A film pickling method to remove the sulfide formed on Cu without causing additional corrosion was developed. • Corrosion damage underneath the sulfide film formed on Cu corroded in sulfide solutions was investigated. • At low SH - concentrations, general surface roughening was observed, with most Cu surfaces corroding to a depth of ≤ 0.5 μm. • At high SH - concentration, film thickening increased Cu(I) transport resistance, reducing micro-galvanic corrosion rate. • The initiation, growth, and stifling mechanism of micro-galvanic corrosion were proposed.