Electrochemical and Quantum Chemical Studies of 3,5-Di(n-Tolyl)-4-Amino-1,2,4-Triazole Adsorption on Mild Steel in Acidic Media

The corrosion inhibition of mild steel by some new synthesized triazole organic-type compounds, the 3,5-di(n-tolyl)-4-amino-1,2,4-triazoles (n-DTAT: n = 2, 3, 4), was investigated in 1 M hydrochloric acid (HCl) and 0.5 M sulfuric acid (H₂SO₄) using weight loss measurements, electrochemical impedance spectroscopy, and polarization curves. The ability of the n-DTAT to inhibit the corrosion of mild steel was dependent on the position of the methyl (CH₃) group on the tolyl substituent. The inhibition efficiency of the tested compounds was found to decrease as follows: 4-DTAT > 3-DTAT > 2-DTAT. Polarization curve studies showed that 4-DTAT is a mixed-type inhibitor in 1 M HCl and cathodic–type in 0.5 M H₂SO₄. This inhibitor acted on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. Study of the effect of temperature showed that the inhibitor efficiency does not depend on temperature. Apparent activation energies were determined. The 4-DTAT appeared to function through the general adsorption mode following the Langmuir adsorption isotherm model in acidic media. The electronic properties of isomers of DTAT, obtained using the Hartree Fock AB initio 3-21G quantum chemical approach, were correlated with their experimental efficiencies.