Organic compounds as corrosion inhibitors for reinforced concrete: a review

With the goal of preventing concrete deterioration by means of destructive corrosion processes, the use of single organic compounds or mixtures as organic corrosion inhibitors (OCIs) instead of inorganic chemicals is becoming a very attractive practice. As OCIs are more ecologically friendly in their production and environmental fate, they have several advantages over well-known inorganic additives such as metallic nitrites, chromates, or arsenates. In this article, the application of different single organic compounds (of either natural or synthetic origin) as well as mixtures that have been used to lengthen the lifespan of concrete structures is reviewed. After a small exemplification of the use of single organic compounds bearing amino, hydroxy, formyl, or carboxylic functionalities, the more often used OCIs are reviewed according to their principal functional group. Afterward, the application of compound mixtures of either synthetic or natural origin, the use of natural extracts, and biomass are surveyed. Finally, the effects of functional groups within the top 10 inhibitor molecules, the toxicity of OCIs, their effects on the physical-mechanical properties of concrete, and their long-term performance are discussed.