The Effects of Cassia Siamea Lam. Root Extract on the Corrosion and Kinetics of Corrosion Process of Copper in Alkaline Solutions

Abstract

The effect of Cassia siamea lam. (CSL) root extract as a corrosion inhibitor of copper in 0.50 M NaOH solutions was investigated using absorbance difference technique at 30 °C and 40 °C. CSL root extract inhibited the corrosion of copper in 0.50 M NaOH solutions and the inhibition efficiency (% IE) increased to a maximum of 78.3±2.3% with increasing concentration of the extract but decreased with increasing temperature. The adsorption of CSL root extract on copper surface followed the Langmuir adsorption model with the average heat of adsorption, Q_ads and free energy of adsorption, ΔG_ads of -8.98 kJmol^-1 and -8.70 kJmol^-1 respectively. A kinetic treatment of the data revealed a first order kinetics with respect to copper in the presence and absence of the extract.