Thermodynamic, chemical and electrochemical investigation of pandanus tectorius extract as corrosion inhibitor for steel in sulfuric acid solutions

Abstract

The corrosion inhibition characteristics of pandanus tectorius extract on corrosion of steel in 1 M H₂SO₄ were investigated using chemical and electrochemical measurements at various temperatures (30, 40, 50 and 60 °C). The effect of acid concentration on the corrosion rate of steel increases with acid concentration (0.25-2.00 M) showing first order corrosion reaction without changing the reaction mechanism. The results showed that when the concentration of pandanus tectorius extract increased from 5% to 15% (v:v), the rate of steel corrosion is decreased, which indicated that pandanus tectorius extract are good inhibitor for steel corrosion in 1 M H₂SO₄ at 30 °C and attains 88.02% at 15% (v:v) from weight loss method. Electrochemical results showed that the investigated extract was acted as mixed type inhibitor. The free energy of adsorption ΔG_ads for pandanus tectorius, indicates that the process was spontaneous and physically adsorbed (physisorption) onto the steel surface. Also, scanning electron microscopy (SEM) is used to support the obtained result. The trend of inhibition efficiency with temperature suggests physical adsorption of this extract on the corroding steel surface. Thermodynamic functions ∆E_app, ∆H* and ∆S* has been calculated and are discussed.