Inhibiting Properties of Some Amines on Corrosion Behaviour of Mild Steel in Phosphoric Acid Solution at Various Temperatures

Abstract

The inhibition effect of triethanolamine, triethlyamine and diethylamine on corrosion of mild steel in phosphoric acid solutions has been studied. The mass loss and polarization techniques have been employed at 302–333 K. Results obtained reveal that all compounds are good inhibitors. The inhibition efficiency of the inhibitors increases with increase in inhibitor concentration. The effect of temperature on corrosion behaviour of mild steel indicates that inhibition of inhibitors decreases with increasing temperature. The inhibition efficiency decreases with increasing concentration of phosphoric acid. At all the inhibitor concentration in 1 and 5 N phosphoric acid solution at 302–333 K for 5 h immersion period, the inhibition efficiency of inhibitors decreases in the order diethylamine > triethylamine > triethanolamine. These inhibitors are fitted to Tempkin’s adsorption isotherm. The values of activation energy and free energy of adsorption have also been calculated. The plots of W_f against time (days) at 302 K give straight line, which suggests that it obeys first order kinetics. The rate constant k and half life time t_1/2 have also been calculated.