Corrosion inhibition studies of the combined admixture of 1, 3-diphenyl-2-thiourea and 4-hydroxy-3-methoxybenzaldehyde on mild steel in dilute acid media

Mild steel corrosion is responsible for economic and industrial losses due to accelerated deterioration. Synthesized derivatives of thiourea and phenolic aldehydes containing heteroatoms are capable of inhibiting corrosion by adsorption onto the steel through formation of strong bonds. Thus, the electrochemical corrosion inhibition properties of the combined admixture of 1,3-diphenyl-2-thiourea and 4-hydroxy-3-methoxybenzaldehyde on mild steel in 1 M H2SO4 and HCl acid media were studied through weight loss analysis, potentiodynamic polarization method, optical microscopy and IR spectroscopy. Results showed that the organic mixture effectively inhibited the corrosion of mild steel in both solutions with an optimal inhibition efficiency of 97.4% and 97.47% in H2SO4 from weight loss and potentiodynamic polarization test, while the corresponding values in HCl were 94.71% and 89.73% respectively. Thermodynamic calculations showed that the compound chemisorbed onto the steel surface blocking the diffusion of corrosive anions. Observations from micro-analytical images confirmed the effective inhibition property of the compound and its presence on the surface topography of the steel. Infrared spectra revealed the presence of the functional groups of the organic compound responsible for corrosion inhibition. The adsorption of the compound was deduced to obey the Langmuir, Frumkin and Freundlich adsorption isotherm.