Polyalthia longifolia as a Corrosion Inhibitor of Brass in Alkaline (KOH) Medium

Abstract

This study evaluates the inhibition efficiency of Polyalthia longifolia leaves extract on brass in an alkaline medium (KOH) using weight loss technique. The weight loss, corrosion rate and inhibition efficiency were determined using standard procedure. FT-IR analysis revealed the presence of some functional groups (- C=O, -C=N, O-H and C-H stretching) indicative of the inherent inhibition potential of the extract. The result showed that the weight loss was higher at 313 K than 303 K and decreased with increasing concentration of the inhibitor. The corrosion rate also increased with increasing concentration of KOH solution and was minimal at 700 mg/dm3. With the addition of inhibitor (Polyalthia longifolia) the inhibition efficiency (% IE) was found to increase in the order: 100mg/dm3 ≤ 1000mg/dm3 at 303K (81.2585% efficiency), and at 313 K (78.3473% efficiency). It also revealed that highest inhibition efficiency was recorded at 303K. The result of SEM analysis showed that the metal surface was protected from corrosion in the presence of plant extract which is acting as an inhibitor. On correlation of the inhibition dynamics to adsorption isotherms, the values of R2; Langmuir (0.5494, 0.2715), Freundlich (0.7950, 0.7948), BET (0.6893, 0.6363) and Temkin (0.8262, 0.8255), showed that of Temkin to be the highest. This indicates that the system under investigation assumes monolayer adsorption on a homogeneous surface and no interaction between adsorbed molecules, making it suitable for chemical adsorption processes.