Significance of π–electrons in the design of corrosion inhibitors for carbon steel in simulated concrete pore solution

Chloride-induced corrosion of carbon steel in reinforced concrete is one of the most important failure mechanisms of reinforced structures. Organic inhibitors from different organic groups were analyzed using cyclic potentiodynamic polarization (CPP) to see their effect on the pitting potential of carbon steel in 0.1 M Cl^– contaminated deaerated simulated concrete pore solution (SCPS). It was found that organic compounds with π– electrons functional groups had better performance. This is attributed to the high density of HOMO energies found between the carbon that is double bonded to oxygen, resulting in high tendency of donating π – electrons to the appropriate vacant p or d–orbitals of the carbon steel, resulting in a chemisorption process. It was found that the best corrosion inhibition performance was achieved by polycarboxylates followed by alkanol amines and amines. Another approach to shows the significance of this phenomenon was by developing a quantitative structure-property relationship (QSPR) using a Signature molecular descriptor which correlates the occurrences of atomic Signatures in a dataset to a property of interest using a forward stepping multilinear regression. Data from literature was incorporated in the model, showing that [O](=[C]) is the most influential part of all the inhibitors analyzed demonstrating the significance of π– bond electrons in the adsorption process. Finally, the QSPR model predicted the pitting potentials for the inhibitors used with a high correlation coefficient.