INHIBITION OF THE CORROSION OF DURALUMIN IN ACIDIC MEDIUM BY GNETUM AFRICANA, OCIMUM GRATISSIMUM AND MUSA ACUMINATA

Author: Ani Chinedum MArtins
Department: Chemical Engineering
Affiliation: Nnamdi Azikiwe University Awka

The inhibitive, thermodynamics and adsorptive properties of ethanol extract of gnetumafricana, ocimumgratissimum and musaacuminata for the corrosion of duralumin in HCL and HN03 solutions was investigated using weight loss technique.The inhibition efficiency of the extract decreased as the temperature and time of immersion increased, but increased with increase in concentration of the extract. The inhibitive potential of the extracts is attributed to the presence of alkaloids, flavonoids, tannin, saponin, cardial glycoside in the extract. FTIR shows that the leaves contain some functional groups such as C-H,aromatic rings and C-O which act as centres of adsorption for the corrosion process and GCMS revealed some organic acids which have corrosion inhibitive property. The heat of adsorption obtained ranged from -7.53to-20.23 kjmol-1 indicating that adsorption of the inhibitors on the surface of duralumin was exothermic,spontaneous and follows the mechanism of physical adsorption. The adsorption of the inhibitors on the surface of duralumin obeyed Langmuir, Temkin,Florry-Huggins,Frumkin and Freundrich adsorption isotherms.Langmuir isotherm best described the corrosion mechanism.The corrosion inhibition process was optimized using the Central Composite Design (CCD) for four factors and the optimization results were analyzed using Design Expert 8.1.0 trial version. The major factors were found to be inhibitor concentration, temperature and acid concentration. Maximum corrosion occurred atacid concentration of 3M, inhibitor concentration of 0.3g/l, time of 5hrs, and temperature of 40oC.The result obtained shows that HCl is more corrosive than HNO3.From the values of the inhibition efficiencies of gnetumafricana, ocimumgratissimum and musaacuminata calculated as 80%, 76.4% and 56.3% respectively, gnetumafricana has the highest inhibition efficiency of 80% .The extracts were found to be good inhibitors for the corrosion of duralumin in HCl and HN03.

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