Computational and experimental evaluation on pyrazoles as corrosion inhibitor in HCl solution: DFT and electrochemical analysis

Traditionally for the selection of effective corrosion inhibitors, various organic compounds are synthesized and their corrosion protective ability is measured but out of large number of tested compounds only few are found efficient which results in time loss, chemical loss and finally money loss. To overcome these problems computational analysis is executed on compounds. For this, initially compounds are analyzed by density functional theory (DFT) calculations and if favorable results are found then only those compounds are synthesized for corrosion inhibition studies. Thus, application of computational analysis has paved the way for the costeffective identification of efficient corrosion inhibitors. In this study corrosion preventing ability of pyrazoles, namely, 2-(3,5-bis(4-methoxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl)-4- H-pyrazol-1-yl)-4- phenylthiazole (BMPP) and 2-(3,5-bis(4-chlorophenyl)-4,5-dihydro-1H-pyrazol-1-yl)-4- H-pyrazol-1-yl)-4- phenylthiazole (BCPP) was studied on N80 steel (NS) in 15% HCl solution using DFT, gravimetric and electrochemical methods. The compounds BMPP and BCPP offered corrosion protection ability of 97.98 and 94.95%, respectively, at 500 ppm concentration towards NS facet through mixed adsorption by obeying Langmuir isotherm. Both compounds exhibited mixed inhibitor nature. The computational predictions about corrosion inhibition behavior of both compounds were in agreement with experimental observations. The results of surface analysis performed by FE-SEM, AFM and XPS suggested the fabrication of inhibitor corrosion protective film at the NS facet.