Aquatic Science and Technology ISSN 2168-9148 2013, Vol. 1, No. 2 www.macrothink.org/ast 135 Corrosion Inhibition of Carbon Steel in 1M HCl Solution Using Sesbania Sesban Extract Hussein H. Al-Sahlanee (Corresponding author) Chemical Engineering Department, Basrah University, Iraq E-mail: Hossein_engineering@yahoo.com Abdul-Wahab A. Sultan Petrochemical Engineering Department, Basrah Technical College, Iraq E-mail: Dr.wahab57@gmail.com Mustafa M. Al-Faize Chemical Engineering Department, Basrah University, Iraq E-mail: Mustafa_alfaize@yahoo.com Received: April 28, 2013 Accepted: June 5, 2013 Published: July1, 2013 doi:10.5296/ast.v1i2.3891 URL: http://dx.doi.org/10.5296/ast.v1i2.3891 Abstract Corrosion inhibition effect of Sesbania sesban extract (SSE) on the carbon steel in 1M HCl solution was investigated by potentiodynamic polarization and weight loss techniques. The corrosion rate of carbon steel was decreased in the presence of SSE. The corrosion inhibition efficiency was found to increase with SSE concentration to attain 91.08% with 2.00 g/l at 25Ԩ. The polarization studies showed that SSE acts as mixed type inhibitor. The effect of temperature, acid concentration and immersion time on the corrosion rate of carbon steel in HCl solution in the absences and presence of SSE was also studied. Values of corrosion inhibition efficiency calculated from weight loss technique were in good agreement with those obtained from potentiodynamic polarization test. The results showed that the adsorption of the extract on the carbon steel surface obeys Langmuir isotherm. The activation parameters, apparent activation energy (E a ሻ, the enthalpy of activation (ΔH a ) and entropy of activation (ΔS a ) for the corrosion of carbon steel in 1M HCl in the absence and presence of SSE were calculated and discussed. Keyword: Corrosion inhibition, Carbon steel, Hydrochloric acid