Inhibition of Corrosion of Zinc in H2SO4 Medium by the Schiff Base, 4-Hydroxy Phenyl Methylidene-2-(1-Phenyl Ethylidene) Hydrazine Carbothioamide (4-HPMHC)

Inhibitive effects of Schiff’s base, 4-hydroxy phenyl methylidene-2-(1-phenyl ethylidene) hydrazine carbothioamide (4-HPMHC) on the corrosion of zinc in H₂SO₄ at temperatures 303 K, 313 K and 323 K were studied using weight loss method. Inhibition efficiency of 4-HPMHC was found to depend on concentrations of inhibitor and the acid, temperature of the process and period of contact. The study revealed that 4-HPMHC inhibits the corrosion of zinc with maximum inhibition efficiency of 86.87% at 0.0005 M of the inhibitor. The kinetics of uninhibited and inhibited corrosion reaction was found to follow first order. Activation energy (Ea) value (18.22 J mol^-1) of the inhibited corrosion system was higher than that of the uninhibited system with value of 4.919 J mol^-1 at 0.0005 M of inhibitor and in 0.05 M of the H₂SO₄ acid. The calculated thermodynamic parameters viz; enthalpy, entropy and free energy of the inhibited reaction suggest that the process is spontaneous and exothermic. An adsorption characteristic of the studied inhibitor was best described by Langmuir adsorption isotherm.

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