Effect of haloazines on corrosion of Steel 3 in hydrochloric acid

• A.G. Berezhnaya, V.V. Chernyavina, I.I. Krotkii and A.V. Gulevskaya

Southern Federal University, ul. Zorge 7, 344090 Rostov-on-Don, Russia

Abstract: The protective effect of 6-iodo-5-(4-methoxyphenyl)naphtho[2,1-a]phenazine (1), 6-iodo-5-(p-tolyl)benzo[a]phenazine (2), 3-bromo-2-(naphthalen-2-yl)pyridine (3), 5-iodo-6-(4-methoxy¬phenyl)naphtho[1,2-f]quinoxaline (4), 6-iodo-5-phenylnaphtho[2,1-a]phenazine (5) and 8-iodo-7-phenylnaphtho[1,2-a]phenazine (6) on steel corrosion in 1 M hydrochloric acid was studied using gravimetry, potentiodynamic polarization and impedance spectroscopy. The new haloazines studied, depending on their chemical structure, provide 61–98.6% steel protection at the highest concentration at 25°C. The effectiveness of the additives decreases with increasing temperature. The best inhibitor is 3-bromo-2-(naphthalen-2-yl)pyridine. At a temperature of 80°C and a concentration of 0.05 mmol/L, the efficiency of this inhibitor is 60%. Quantum-chemical calculations of the key parameters of the organic molecules were performed. A good correlation of efficiency with the calculated parameters of the molecules obtained within the scope of the density functional theory (DFT) B3LYP/3-21G has been found. It was found that the additives inhibit both partial electrode reactions of the corrosion process. The mechanism of the inhibitors’ protective action was determined.

Keywords: inhibitor, low-carbon steel, hydrochloric acid, haloazines, DFT

Int. J. Corros. Scale Inhib., 2026, 15, no. 1, 107-116
doi: 10.17675/2305-6894-2026-15-1-5

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