Molecular structural aspects of organic corrosion inhibitors: Influence of -CN and -NO2 substituents on designing of potential corrosion inhibitors for aqueous media

The organic compounds containing -CN and -NO2 substituents are extensively used as metal corrosion inhibitors. The -CN and -NO2 substituents are electron withdrawing in nature and they expected to decrease the inhibition efficiency of organic inhibitors because of their -R-effect and/or -I-effect. However, either in too big or too small organic inhibitors, -CN and -NO2 substituents increase the inhibition effectiveness of the inhibitors. These substituents also affect the solubility of their base compounds in polar electrolytes. Inhibition effectiveness of macromolecules, oligomers and polymers expected to increase in the presence -CN and -NO2 substituents. Computational based analyses using Density functional theory (DFT, molecular dynamics' (MD) and Monte Carlo (MC) simulations showed that -CN and -NO2 substituents greatly affect the charge sharing reactions taking place between metal and organic inhibitors. Orientation of the organic inhibitors over the metallic surface is also greatly depends upon the presence of -CN and -NO2 substituents. In general, the -CN and -NO2 containing moieties acquire vertical orientation and cover fewermetallic surface area. Present reviewarticle features the collection of somemajor publications that are published on recent advancements in the field of corrosion inhibition using -NO2 and -CN substituents containing compounds. The description of present article will leads to the designing and synthesis of effective corrosion inhibitors. (C) 2020 Elsevier B.V. All rights reserved.