Abstract
Thermodynamic, kinetic and adsorptive parameters of methanolic extract of leaves of Cochlospermum tinctorium as eco-friendly inhibitor for the corrosion of mild steel in HCl medium were evaluated through the weight loss method at 303 K and 311 K. The inhibition efficiency, %IE, increased with increase in extract concentration, but found to be better at 303 K than 311 K. The decrease in %IE with increase in temperature with the average value of 81.88 kJ/mol for activation energy, E a , and the values of free energy, ÄG, for the adsorption process are all supportive of physical adsorption mechanism. The values of heat of adsorption, Q ads,, are all negative, an indication that the adsorption process was exothermal. The half-life, t 1/2 , value increased with increase in inhibitor concentration and low at high higher, implying the inhibitor performance increased with increase in the extract concentration and decreased with rise in temperature. The data best fitted the Langmuir adsorption isotherm.
Highlights
Humanity has come to terms with the repercussions and the environmental accidents that our behaviour has impacted on the earth, putting it in a compromising future
The extract has inhibitive effect on the corrosion of mild steel in HCl medium as it can clearly be seen from Table 1 that the corrosion rate decreases and IE% increases with increase in the extract concentration at the two temperatures
The inhibitor performance is higher at the lower temperature, suggestive of physical adsorption mechanism for adsorption of the
Summary
Humanity has come to terms with the repercussions and the environmental accidents that our behaviour has impacted on the earth, putting it in a compromising future. The focus on plant extracts, away from synthetic inhibitors, as eco-friendly inhibitors for metal corrosion prevention is due mainly to economic reasons, strict environmental regulations, renewability and biodegradability (Arora et al, 2007; Selviet al., 2009, Alaneme and Olusegun, 2012). The extracts such natural substances contain mixtures of compounds having oxygen, nitrogen, sulphur and phosphorus which help in corrosion inhibition process (Jai and Ali, 2008). The species Cochlospermum tinctorium, the plant of interest in this work, is a widely distributed plant within the savanna areas of West and Central Africa (Etuket al., 2009). The thermodynamic, kinetic and adsorptive parameters of the inhibition process were evaluated at two temperatures of 303 Kand311 K, a narrow temperature range employed to maintain the molecular structure(s) of the component(s) responsible for the inhibition process in the course of the experiment
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