Abstract
D-glucose derivatives of dihydropyrido-[2,3-d:6,5-d′]-dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone (GPHs) have been synthesized and investigated as corrosion inhibitors for mild steel in 1M HCl solution using gravimetric, electrochemical, surface, quantum chemical calculations and Monte Carlo simulations methods. The order of inhibition efficiencies is GPH-3 > GPH-2 > GPH-1. The results further showed that the inhibitor molecules with electron releasing (-OH, -OCH3) substituents exhibit higher efficiency than the parent molecule without any substituents. Polarization study suggests that the studied compounds are mixed-type but exhibited predominantly cathodic inhibitive effect. The adsorption of these compounds on mild steel surface obeyed the Langmuir adsorption isotherm. SEM, EDX and AFM analyses were used to confirm the inhibitive actions of the molecules on mild steel surface. Quantum chemical (QC) calculations and Monte Carlo (MC) simulations studies were undertaken to further corroborate the experimental results.
Highlights
Against HIV infection, cancer, diabetes, etc. in addition to their antibiotics, anti-inflammatory, antimalarial, antiviral, and glycosylation inhibitors properties[21,22,23]
(1) All studied molecules act as good inhibitors for mild steel corrosion in 1 M hydrochloric acid solution and the order of inhibition efficiencies for both gravimetric and electrochemical results is GPH-3 (97.82%) >GPH-2 (95.21%) >GPH-1(93.91%).The presence of electron releasing hydroxyl (-OH) and methoxy (-OCH3) groups in GPH-2 and GPH-3 respectively, showed the higher inhibition efficiency as compared to inhibitor without any substituents (GPH-1)
(5) Quantum chemical calculations carried out for neutral, protonated and aqueous forms of the inhibitors supported the experimental order of inhibition efficiency
Summary
Against HIV infection, cancer, diabetes, etc. in addition to their antibiotics, anti-inflammatory, antimalarial, antiviral, and glycosylation inhibitors properties[21,22,23]. Chemical transformations that involve using hexoses glucose together with other biologically and industrially useful chemicals has become a top research topic in the recent time. This is because hexoses are comparatively more abundant and remains one of the primary renewable resources based natural feedstock chemicals[24,25]. Careful examination of the literature revealed that carbohydrates and their derivatives such as chitosan show excellent corrosion inhibiting properties[26,27,28]. It is worthy of mention that glucose based compounds were chosen as corrosion inhibitors in this study because, precursors such as glucose and aniline are readily available and relatively cheaper. The results of the weight loss, electrochemical, surface and computational analyses were in good agreement
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