Corrosion inhibition of steel by Coriander extracts in hydrochloric acid solution

Corrosion inhibition of steel using an aqueous extracts of coriander (coriander sativum) and some natural additives (paprika,clove,cinnamon,black piper and pomegranate husk) in 0.5 m hcl was investigated using electrochemical polarization and eis methods. the results indicate that the corrosion inhibition efficiency increases with an increasing coriander extract concentration,when coriander extract concentration exceeds 900 ppm the inhibition efficiency decreases. the addition of 87.5 ppm of some additives to a solution containing 0.5 m hcl and 300 ppm of coriander extract enhanced the corrosion inhibition process in the following order: paprika > clove>cinnamon > black piper > pomegranate husk the effect of temperature on the corrosion behavior of steel indicates that inhibition efficiency of the coriander extract decreases with the rise of temperature. the adsorption isotherm of coriander extracts on the steel has been determined and found to follow langmuir adsorption isotherm where the negative value of free energy of adsorption indicates that the adsorption of the coriander extracts on the steel surface occurs spontaneously.