Moringa Oleifera Seed Oil as Green Corrosion Inhibitor for Ductile Cast Iron in Cassava Fluid

Abstract

Cassava fluid is acidic and corrodes the ductile cast iron parts from which many machineries used in processing cassava, a staple source of carbohydrates in most West African countries are made. The corrosion behavior of ductile cast iron cassava fluid with Moringa Oleifera seed oil as inhibitor was studied using 0, 0.2, 0.4, 0.6, and 0.8 %v/v concentrations and at two different temperatures of 40oC and 60oC by potentiodynamic polarization (Tafel) technique. Some thermodynamic, Corrosion inhibition and adsorption studies were also addressed. Moringa Oleifera seed oil extract was found to successfully inhibit the corrosion of cast iron in cassava fluid. Moringa Oleifera acted as a mixed type inhibitor. The corrosion inhibition efficiency was found to increase with increase in concentration of the extract but decrease with rise in temperature. The maximum inhibition efficiency of the extract on ductile cast iron corrosion was noted to be about 73%. Adsorption studies showed that Langmuir isotherm describes the manner in which the inhibitor was adsorbed on the metal surface. The adsorption process was found to be spontaneous as all the free energy of adsorption values calculated were negative and ranged from -3.43 kJ/mol to -1.34 kJ/mol, signifying a spontaneous physical adsorption on metal surface. The stereo-micrograph images of the metal surface after immersion in corrosive medium confirmed the protection offered by the Moringa Oleifera extract on the surface of the metal. It was further shown that the corrosion rate was influenced by the combined interactions of temperature of operation and concentration of the inhibitor.