POTENTIODYNAMIC BEHAVIOUR OF TIN ELECTRODE IN SOME CARBOXYLIC ACIDS SOLUTIONS

Document Type : Original Article

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Chemistry Department, Faculty of Science (for Girls), AL- Azhar University, Nasr City, Cairo, Egypt

Abstract

Potentiodynamic behaviour of tin electrode in citric, oxalic, maleic and malic acids was studied at room temperature. The various electrochemical parameters were calculated. In addition, the metallographic structure of tin surface electrode was examined for some solutions using scanning electron microscope (SEM). The anodic E/I curves were characterized by active - passive transition state.  The anodic active region was due to the formation of soluble Sn(II) species. The passivity of tin anode was related to the hydrolysis of Sn(IV) and precipitation of Sn(OH)4 film on the anode surface. The addition of different percentages of sucrose to (1 M) of all organic acids used inhibited the anodic dissolution of tin electrode and enhanced the attainment of passivity. While the addition of sodium chloride accelerated the corrosion of tin and delayed the establishment of passivation. In citric, maleic and malic acids, inhibition was of mixed type and occurred by adsorption of SnL complex molecules following the Temkin isotherm. In case of oxalic acid the inhibition was found to be predominantly anodic occurring by adsorption of SnL2 complex and following the Langmuir isotherm.…

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Al-Azhar Bulletin of Science
Volume 18, Issue 2-A
December 2007
Pages 47-61

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