Atmospheric Corrosion Mechanisms in Steel Alloys

Atmospheric corrosion of steel alloys arises from the electrochemical interaction of metallic iron with water films, oxygen and airborne pollutants. At exposed surfaces, microscopic anodic regions dissolve to release ferrous ions, while adjacent cathodic areas sustain oxygen reduction. The resulting rust comprises stratified iron oxides and oxyhydroxides whose composition and morphology depend on relative humidity, time-of-wetness, temperature and the presence of aggressive species such as chloride and sulphur dioxide. Localised galvanic couplings between alloy phases or corrosion products can intensify attack, leading to pitting and crevice formation. Alloying elements such as chromium, nickel and copper modify rust composition and adherence by influencing oxide thermodynamics and electronic conductivity. In marine atmospheres, chloride promotes formation of akaganeite and green rust, which alter layer permeability and diffusion paths for corrosive ions and oxygen. In industrial and urban settings, sulphate and nitrate depositions foster complex mixed oxide films. Advances in sensor technologies and data-driven modelling now enable quantification of dynamic corrosivity and prediction of long-term performance. Understanding these mechanisms underpins the design of steel alloys and protective coatings for infrastructure, transportation and energy applications worldwide.

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Atmospheric Corrosion Mechanisms in Steel Alloys publication trend

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Technical terms

Electrochemical cell: Localised circuit formed by anodic metal dissolution and cathodic oxygen reduction enabling corrosion.

Time-of-wetness (TOW): Proportion of time a metal surface remains covered by a moisture film conducive to corrosion.

Corrosion product layer: Stratified film of oxides and oxyhydroxides on steel that governs ion diffusion and layer protectiveness.

Green rust: Mixed Fe(II)/Fe(III) hydroxide chloride phase that forms under chloride-rich conditions and alters rust structure.

Akaganeite: Chloride-stabilised iron oxyhydroxide (β-FeOOH) commonly found in marine atmospheric corrosion.

References

1. Towards understanding and prediction of atmospheric corrosion of an Fe/Cu corrosion sensor via machine learning. Corrosion Science (2020).
2. Reviewing machine learning of corrosion prediction in a data-oriented perspective. npj Materials Degradation (2022).
3. Corrosion of Carbon Steel in Marine Environments: Role of the Corrosion Product Layer. Corrosion and Materials Degradation (2020).
4. The role of chromium content in the long-term atmospheric corrosion process. npj Materials Degradation (2020).