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.

Author(s): Onwu FK, Ogueji C and Mgbemena NM

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