text: Although in the aforementioned example, oxic conditions were always considered with the reduction of dissolved  in the cathodic zones, pitting corrosion may also occur under anoxic, or reducing, conditions. Indeed, the very harmful reduced species of sulfur (, , , , , S and ) can only subsist under reducing conditions. Moreover, in the case of steel and stainless steel, reducing conditions are conducive to the dissolution of the protective oxide layer (dense γ-) because  is much more soluble than , and so reducing conditions contribute to the breakdown of the protective oxide layer (initiation, nucleation of the pit). Reductants exert thus an antagonist effect with respect to the oxidants (chromate, nitrite) used as corrosion inhibitors to induce steel repassivation via the formation of a dense γ- protective layer. Pitting corrosion can thus occur both under oxidizing and reducing conditions and can be aggravated in poorly oxygenated waters by differential aeration, or by drying/wetting cycles.
  Under strongly reducing conditions, in the absence of dissolved oxygen in water, or pore water of the ground, the electron acceptor (oxidizing agent) at the cathodic sites, where reduction occurs, can be the protons () of water itself, the protons of hydrogen sulfide (), or in acidic conditions in case of severe pyrite oxidation in a former oxic atmosphere, dissolved ferric ions (), known to be very potent oxidizers. The presence of harmful reduced species of sulfur and microbial activity feeding the sulfur cycle (sulfide oxidation possibly followed by bacterial sulfate reduction) have also to be taken into account. Strictly abiotic (i.e. inorganic) corrosion processes are generally slower under anoxic conditions than under oxic conditions, but the presence of bacteria and biofilms can aggravate the degradation conditions and causes unexpected problems. Critical infrastructures and metallic components with very long service life may be susceptible to pitting corrosion: for example the metallic canisters and overpacks aimed to contain vitrified high-level radioactive waste (HLW) and spent nuclear fuel and to confine them in a water-tight enveloppe for several tenths of thousands years in deep geologic repositories.