Protective mechanism of weathering steel rust layers in atmospheric environments and their stabilization treatment technologies

Corrosion is a major cause of steel degradation, leading to material thinning, perforation, stress concentration, and ultimately deterioration of mechanical properties that can result in engineering structure failures. Weathering steels are extensively used across various applications, such as bridges, buildings, and vehicles, and are recognized for being economical and environmentally friendly. These steels can spontaneously develop protective rust layers, which are stable, compact, and adhesive, effectively inhibiting direct contact between corrosive media and the steel substrate, thereby offering superior corrosion resistance in atmospheric environments. Ideally, the corrosion resistance of the weathering steel rust layer improves with increased exposure time, though various factors can influence this behavior. This study discusses the protective properties of rust layers from multiple perspectives, including their internal and external structure, composition, formation mechanism, the influence of environmental factors and alloying elements on corrosion resistance, and current treatment technologies for rust stabilization. The rust stabilization treatment technology has been examined from its historical development to its current state and future direction. The initial process of rust formation has been described, beginning with localized sites that gradually coalesce. The dual-layered structure of rust has been introduced, and recent studies have proposed a multi-layered structure, with the specific contribution of each layer clarified. The influence of alloying elements and environmental factors, such as salinity, temperature, humidity, and irradiation, on the formation and stabilization of protective rust layers has been discussed in detail. Additionally, the impact of traditional elements like Cr, Cu, and Ni, as well as other elements such as Sn, Mo, and rare earth elements, on the formation of effective corrosion products, the nucleation of rust layers, and the compactness and bonding strength of the rust has also been analyzed. Most alloying elements enhance the protective properties of rust layers by improving their compactness, stability, and ionic selectivity. Research into evaluating the corrosion resistance of rust layers has now expanded to include artificial intelligence, advanced sensors, and big data technologies, making studies more dynamic and efficient. However, there remains a lack of research on the effects of complex atmospheric environments (such as marine-industrial complex environments) and the influence of multiple alloying elements coexisting. Clarifying the impact of each factor is challenging due to potential synergistic effects. Moreover, the conditions required for the formation of integral and stable rust layers are very stringent, and such protective rust layers may not form in harsh environments. Therefore, appropriate protective measures are still strongly recommended. This study specifically discusses the currently available rust stabilization treatment technologies, introducing key technical approaches such as coating technology, spraying technology, and surface reconstruction of the rust layer. These methods are crucial for enhancing the reliability, stability, and applicability of weathering steels. The development of efficient and environmentally friendly rust stabilization treatment technologies represents a promising area for future research.