Protective Mechanism of Weathering Steel Rust Layer in Atmospheric Environment and Its Stabilization Treatment Technology

Corrosion is a major form of steel loss, which results in material thinning, perforation, and stress concentration, triggering deterioration of mechanical properties, ultimately causing failure of the engineering structure and safety accidents. Weathering steels are widely used in various fields (e.g. bridges, buildings, and vehicles) and are recognized as economical and environment-friendly steel materials. Protective rust layers can spontaneously form on weathering steels. Stable, compact and adhesive rust layers can effectively inhibit the contact between corrosive media and steel substrate, which exerts superior corrosion resistance in natural environment. With the increase of exposure time length, the corrosion resistance of the weathering steel rust layer becomes more evident. This paper elaborated the protective mechanisms of weathering steel rust layer from the aspects of inner/outer structure, the composition and the formation mechanism of rust layers. The effects of alloying elements and environmental factors (salinity, temperature, humidity, and irradiation) on the formation and stabilization of protective rust layers have been discussed in details. However, there is still a lack of study on the protective rust layers especially on the effect of complicated atmospheric environment (e.g. marine-industrial complex environment), the negative effect of the co-existence of multi alloying elements. Besides, the forming condition of integral and stable rust layers is strict, and the protective rust layers even cannot form in harsh environments. To resolve problems that may exist before stabilization of the rust layer and to ensure the stable formation of the rust layer on the weathering steels, it is still recommended to take appropriate protective measures. This paper also particularly discussed the available rust stabilization treatment technology, which is highly important for improving the reliability, stability and applicability of weathering steels. The development of efficient and environment-friendly rust stabilization treatment technology would be an important research area in the future.