Journal ofthe Korean Chemical Society 2009, Vol. 53, No. 5 Printed in the Republic of Korea 중 산소듐 용 에서 납의 부식방지제인 자연산물질들 M. Abdallah*, A. Y. El-Etre, E. Abdallah, and Salah Eid Chemistry department, Faculty ofScience, Benha University, Benha, Egypt ( 2009. 6. 16; 2009. 7. 20; 2009. 8. 6) Natural Occurring Substances as Corrosion Inhibitors for Tin in Sodium Bicarbonate Solutions M. Abdallah*, A. Y. El-Etre, E. Abdallah, and Salah Eid Chemistry department, Faculty ofScience, Benha University, Benha, Egypt (Received June 16, 2009; Revised July 20, 2009; Accepted August 6, 2009) 요 약. 0.1 M     ,                .                   .     .               .       , Freundlich     . ,                 . 주제어:   , , , , , ABSTRACT. The inhibitive action of the aqueous extract of lawsonia, licorice root and carob toward the corro- sion of tin electrode in 0.1 M NaHCO3 solutions was investigated using galvanostatic polarization measurements. It was found that the corrosion rate decreases in the presence of these extracts indicating the inhibiting of these compounds. The inhibition efficiency increases with increasing extract concentration. The inhibition action of these extracts was explained in view of adsorption of its compounds onto the tin surface, making a barrier to mass and charge transfer. The adsorption of these extracts on the tin surface was found to be a spontaneous process and follow Freundlich adsorption isotherm. It is also found that these extracts provide a good protection to tin against pitting corrosion in chloride containing solution using potentiodynamic anodic polarization technique. Keywords: Corrosion inhibitor, Tin, Lawsonia, Licorice root, Carob, Natural products INTRODUCTION The corrosion studies of tin are closely related to its wide application in industry. The corrosion beha- vior of tin and its inhibition has been studied gal- vanostatically and potentiodynamically in alkaline media.1-10 Most of corrosion inhibitors are organic compound having hetero atoms in their aromatic or long carbon chain. However, there is increasing con- cern about the toxicity of most corrosion inhibitors. The toxic effect does not only affect living orga- nisms but also poison the environment.11 Due to the toxicity of some corrosion inhibitors, there has been increasing search for green corrosion inhibitors.12 Inhibitors in this class are those that are environmen- tally friendly and are gotten from natural product -485-