N-hydroxypyrazine-2-carboxamide as a new and green corrosion inhibitor for mild steel in acidic medium: experimental, surface morphological and theoretical approach.

In this research work, N-hydroxypyrazine-2-carboxamide (NHP) is first introduced as a green, new and effective corrosion inhibitor to protect mild steel (MS) surface from corrosion destruction in a 1 M HCl aggressive solution. Experimental techniques such as gravimetric analysis and electron impedance spectroscopy (EIS) were used in the present analysis; the obtained results show that the inhibition efficiency for NHP was 93.51% at 200 ppm and 298K temperature. NHP molecules adsorbed on mild steel surface followed by Langmuir adsorption model. Similarly, the energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM) analyses were used to describe the changes in surface morphology and composition of MS surface, respectively. Quantum chemical analyses based on density functional theory (DFT) were also applied to calculate the frontier molecular orbitals, that is, EHOMO and ELUMO values for NHP inhibitor molecules; the DFT results are in good correlation with experimental results. Additionally, the studied inhibitor molecule does not produce any environmental threats and toxicity as it decomposed into amine and carbon dioxide and also pyrazine molecules are mainly used as drug precursors showing its green nature. [ABSTRACT FROM AUTHOR]