Review of Corrosion Inhibitors in Reinforced Concrete: Conventional and Green Materials

The corrosion of metals has been a major technical, environmental, and financial challenge for many industries and has become a widespread problem in concrete structures and buildings. Various techniques such as utilization of synthetic corrosion inhibitors have been developed to provide sufficient corrosion protection to reinforcing steel. The application of green corrosion inhibitors, however, has recently attracted increasing attention since these sustainable materials decrease the rate of corrosion and increase the durability and service life of reinforced concrete structures effectively. Considering the emerging field of sustainable corrosion management, many researchers have evaluated various green corrosion inhibitors, reporting scattered results. Consequently, there is a need for a comprehensive study to review, compare, and consolidate their findings in order to identify research gaps and critical trends for further research. This article reviews the properties and effects of various inhibitors including those nontoxic environmentally friendly inhibitors functioning at high pH in concrete. It classifies a broad range of corrosion inhibitors and identifies their advantages and disadvantages. Furthermore, it proposes a set of selection criteria to choose the appropriate inhibitors based on their characteristics and sustainability requirements. It can be concluded that natural corrosion inhibitors show promising potential for extending the service life of reinforced concrete structures as a cost-effective and sustainable solution. Further investigation, however, is demanded for evaluating their technical properties including modelling functional groups for corrosion protection and their effectiveness under combined attack of corrosive ions. The findings of this paper identify the main research trends and can guide researchers to develop further research in the identified gaps towards sustainable progress in the field of civil engineering and corrosion management. It also helps practitioners in all relevant disciplines to gain effective knowledge on emerging green corrosion inhibitors.