Thermodynamics and Kinetics of Inhibition of Aluminum in Hydrochloric Acid by Date Palm Leaf Extract

The corrosion behavior of commercial aluminum in HCl was investigated by gravimetric method in absence and presence of date palm leaf extract (DPLE) as inhibitor. Corrosion rates in absence of extract ranged from 2.4-8.0 mg/cm²/h in the temperature range 20- 50ºC but decreased down to 0.30-2.6 mg/cm²/h in presence of the inhibitor. Hot-water extract of date palm leaves has shown inhibition efficiency (IE) of 40- 88% at the tested conditions. IE was found to increase with increasing inhibitor concentration from 0.2 to 0.6 g/L and decrease as temperature increased. Data showed that Langmuir adsorption isotherm represents surface coverage versus extract concentration data indicating that inhibition is due to monolayer adsorption of extract components on aluminum surface. Low activation energy and enthalpy values support physical adsorption mechanism. SEM-EDS microanalysis of aluminum surface supported the inhibitive effect of the extract at the metal surface.

Keywords
Green inhibitor; corrosion rate; inhibition thermodynamics; inhibition kinetics; aluminum; hydrochloric acid; date palm leaf extract; Phoenix dactylifera