N?-[4-(diethylamino)benzylidine]-3-{[8-(trifluoromethyl) quinolin-4-yl]thio}propano hydrazide) as an effective inhibitor of mild steel corrosion in acid media

Abstract

N?-[4-(diethylamino)benzylidine]-3-{[8-(trifluoromethyl)quinolin-4-yl]thio}propano hydrazide (DEQTPH) was newly synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H<inf>2</inf>SO<inf>4</inf> (0.5 M, 1 M) solutions using weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization method. The corrosion inhibition efficiencies measured by all the above three techniques were in good agreement with each other. The mild steel samples were also analyzed by scanning electron microscopy (SEM). The results showed that DEQTPH is an excellent inhibitor for mild steel in acid media. The inhibition efficiency in different acid media was found to be in the order, 0.5 M H<inf>2</inf>SO<inf>4</inf> > 1.0 M HCl > 2.0 M HCl > 1.0 M H<inf>2</inf>SO<inf>4</inf>. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. It acts as an anodic inhibitor. In the 30-60 °C temperature range, the DEQTPH adsorption follows Langmuir isotherm model. The protection efficiency increased with increasing inhibitor concentration in the range 0.2 × 10-4 to 10.5 × 10-4 M and slightly increased with increasing temperature. Thermodynamic characteristics were discussed. Chemisorption mechanism is proposed. © 2009 Elsevier B.V. All rights reserved.