The inhibiting action, thermodynamics, and adsorptive properties of 1, 2, 4-triazolo1, 5-apyrimidine (TP) have been investigated for the corrosion of mild steel in 0.5 M H2SO4 and 0.5 M H3PO4 solutions by means of potentiodynamic, electrochemical impedance spectroscopy techniques and quantum chemical calculations. Results obtained revealed that TP is more effective in 0.5 M H3PO4 than in 0.5 M H2SO4. Theoretical fitting of different adsorption isotherms such as Langmuir, Flory-Huggins, Temkin, and the kinetic-thermodynamic models were tested. The obtained experimental data fitted all the applied adsorption isotherms except Langmuir. The thermodynamic activation parameters were calculated. The potential of zero charge was also determined using AC measurements to clarify the nature of surface charge of the mild steel in both acidic solutions. Quantum chemical parameters were calculated and explained. The data explained that the inhibition of mild steel in both acidic solutions takes place through physicochemical adsorption mechanism.
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