Synthesis, characterization of novel coumarin dyes as corrosion inhibitors for mild steel in acidic environment: Experimental, theoretical, and biological studies

The new azo acetyl coumarin derivatives were synthesized and characterized using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H NMR) and mass spectral studies. The ability for these three dyes to act as corrosion inhibitors for mild steel in 1.0 M HCl was confirmed by potentiodynamic polarization (PP) and electrochemical impedance spectroscopy (EIS). The state of mixed adsorption with the PP effect is shown. The azo acetyl coumarin derivatives showed the strongest corrosion inhibition of 85.29–93.01% at a corrosion of 7.5 × 10−4 M. Adsorption of the inhibitory molecules on the mild steel surface followed Langmuir adsorption isotherm. The adsorption phenomenon was verified using UV–Vis, scanning electron microscopy (SEM) and Energy dispersive X-ray spectroscopy (EDX) technique, whereas FTIR confirmed the presence of several functional groups containing heteroatoms. Also, quantum chemical parameters, inductively coupled plasma atomic emission spectroscopy, and the anti-bacterial effect of these new derivatives against sulfate reducing bacteria (SRB) were studied. All obtained results ensure that these derivatives can form an effective blocking layer and control the corrosion process.