ANTI-CORROSION POTENTIALS OF FRESH EXTRACTS OF OLD PERSEA AMERICANA VAR. AMERICANA SEED IN 0.5 M H2SO4 ON MILD STEEL

Abstract

An experiment to determine effective corrosion inhibition of fresh extracts from matured seed of Persea Americana var. Americana on mild steel in 0.5 M H₂SO₄ conditions was carried out using gravimetric and electrochemical methods. The tests were carried out at room temperature for 24 hours, and also for higher temperature from 40^oC to 70^oC for 3 hours.  The results showed that the seed extracts have appreciable corrosion inhibition potentials which decreased with increase in temperature. Inhibition efficiency showed that it increased with increase in inhibitor concentration across the same temperature, and similarly decreased with increase in temperature within the same concentration range. The experimental data fitted in with the Langmuir isotherm which is an indicator that the extract constituents were adsorbed on the steel surface. The Arrhenius equations showed a general increase implying that physisorption rather than chemisorptions is prevalent. The values of the heat of adsorption are all negative for temperatures at 40^oC, indicative of the fact that inhibition efficiency decreases with rise in temperature, a proof that the inhibition trend was physisorption.  At temperatures of 70^oC, the values are mixed, some negative and some positive.  This indicates that both physisorption and chemisorptions abound at higher temperatures.  The result from potentiodynamic tests shows that reduction in current potential in the presence of the inhibitor at both concentrations implies that it is a mixed inhibitor.

Keywords: Corrosion inhibition; Fresh; Higher temperatures; Langmuir isotherm; Matured; Persea Americana var. Americana.

DOI: 10.7176/CMR/13-2-03

Publication date:June 30^th 2021