Chromenopyridin derivatives as environmentally benign corrosion inhibitors for N80 steel in 15% HCl

This research work was to investigate the corrosion inhibition performance of two newly synthesized chromenopyridine derivatives namely 2,4-diamino-5-(phenylthio)-5H-chromeno[2,3-b]pyridine-3-carbonitrile (PPC-1) and 2,4-diamino-5-phenoxy-5H-chromeno[2,3-b]pyridine-3-carbonitrile (PPC-2) as potential environmentally friendly corrosion inhibitors for N80 steel in 15% hydrochloric acid (HCl). Various techniques like gravimetric, electrochemical impedance spectroscopy (EIS), Tafel polarizations, scanning electron microscope (SEM) and atomic force microscopy (AFM) have been used. The inhibition efficiencies given by PPC-1 and PPC-2 at 200 mg L−1 are 92.4% and 82.1% respectively. Tafel polarization revealed that both inhibitors are cathodic in nature. Langmuir adsorption isotherm was found to be the best fit. The experimental result was further supported by quantum chemical study.