Recent progress and challenges of using smart corrosion inhibitors in reinforced concrete structures

Corrosion of steel in reinforced concrete (RC) structures has become a major problem worldwide, inevitably leading to very high maintenance and repair costs. Directly admixing corrosion inhibitors in cementitious materials when concrete casting or migrating them to RC structures at the later stage can delay or mitigate steel corrosion to a certain extent, which is a low-cost and high-efficient traditional strategy towards corrosion protection. However, it is also accompanied by several negative impacts on the hydration process of cementitious materials and the mechanical properties of RC structures. Therefore, based on the encapsulation of corrosion inhibitors in micro/nano-containers, the application of smart corrosion inhibitors provides a promising approach to delay the corrosion process of steel and extend the service life of RC structures. These smart corrosion inhibitors can be triggered to release as needed, offering responsive protection against corrosion. In this paper, a variety of environmental stimulations and active response mechanisms of smart corrosion inhibitors in cementitious materials and coated steels are reviewed. Furthermore, it also highlights the current challenges and unexplored possibilities in the design and synthesis of smart corrosion inhibitors, while future perspectives are provided for their engineering application in RC structures.