• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.485-490
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• 2009

The inhibitive action of the aqueous extract of lawsonia, licorice root and carob toward the corrosion of tin electrode in 0.1 M $NaHCO_3$ 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.