Corrosion inhibition of mild steel in acid media by quinolinyl thiopropano hydrazone

Abstract

3-{[8-(trifluoromethyl)quinolin-4-yl]thio}-N'-(2,3,4-trihydroxybenzylidene)propano hydrazide (TQTHBH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl and H2SO4 solutions using weight loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency results obtained by all the above three techniques were in good agreement with each other. Scanning electron microscopy (SEM) technique is used to confirm the effectiveness of inhibition of mild steel corrosion in acid media. The results showed that TQTHBH is a good inhibitor for mild steel in acid media. The inhibition efficiency of TQTHBH in different media was in the following order: 2 M HCl < 1 M H2SO4 < 1 M HCl < 0.5 M H2SO4. The inhibition was assumed to occur via adsorption of the inhibitor molecule on the metal surface. The adsorption follows Langmuir isotherm. TQTHBH acts as an anodic inhibitor. The protection efficiency increased with increasing inhibitor concentration in the range 0.222 x 10^-4 – 11.086 x 10^-4 M, also slightly increased with increasing temperature. Chemisorption mechanism is proposed. The apparent activation energies and enthalpies for the adsorption process were determined. The fundamental thermodynamic functions were used to gain information about TQTHBH inhibitory behaviour.