Corrosion Inhibition Potentials of Fresh Extracts of Matured Avocado Pear (Persea americana var. Americana) Seed Using Gravimetric and Electrochemical Methods

This chapter highlights about Corrosion inhibition verification of fresh extracts from matured seed of Persea americana var. Americana on mild steel in 0.5 M H2SO4 using gravimetric and electrochemical methods. Avocado pear (Persea americana Mill.) crop is cultivated and highly demanded internationally because of the growing demand for fruit and food products. Gravimetric methods were conducted on mild steel coupons of stated dimensions. The tests were carried out at room temperature for 24 hours, and also for higher temperature from 40oC to 70oC for 1 hour. The results showed that the seed extracts have appreciable corrosion inhibition potentials which decreased with increase in temperature. Inhibition efficiency varied considerably with temperature. The Langmuir isotherm, which is a sign that the extract constituents were adsorbed on the steel surface, was compatible with the experimental data. The general increase in the Arrhenius equations suggests that physisorption rather than chemisorption is more common. The values of the heat of adsorption are all negative for temperatures at 40oC, indicative of the fact that inhibition efficiency decreases with rise in temperature, a proof that the inhibition trend was physisorption. Increase in inhibitor concentration leads to a corresponding increase in inhibition efficiency, though the values are less than the case of the experiment at room temperature. The adsorption of natural corrosion inhibitors on metal surfaces is influenced by a number of factors including nature of metal, testing media, chemical structure of inhibitor, nature of substituents present in the inhibitor, presence of additives, solution temperature, and solution concentration. At temperatures of 70oC, the values are mixed, some negative and some positive. This indicates that both physisorption and chemisorptions abound at higher temperatures. According to the results of potentiodynamic tests, a mixed inhibitor is implied by a decrease in current potential when the inhibitor is present at both concentrations.