EFFECT OF INORGANIC ACID SOLUTIONS ON ELECTROCHEMICAL BEHAVIOR OF TIN ELECTRODE

Document Type : Original Article

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

Abstract

The electrochemical behavior of tin metal was studied in some inorganic acid solutions; HCl, HNO3, H2SO4 and H3PO4, using the open circuit potential measurements and the potentiodynamic polarization technique. In addition, the metallographic structure of tin electrode was examined before and after immersion in test solution by using scanning electron microscope (SEM). The identification of the elements presented in the surface of specimen after immersion in different solutions was performed using an energy dispersion X-ray analysis(EDAX). The obtained results demonstrated that the aqueous dilution of HCl, H2SO4 and H3PO4 retarded the corrosion of tin electrode, (hydroxyl ion plays a part in basic salt formation), while dilution of HNO3 acid accelerated the corrosion. It is evident from SEM image that, there were grain boundaries and the surface was more active and rougher in case of mechanically polished electrode. In non-polished electrode, the surface was covered with a protective layer; generally SnO2. In potentiodynamic polarization study, the formation of basic salt Sn(OH)Cl was  preference to any other oxide in HCl solutions. The increase in NO2 concentration was responsible for the increase in the rate of dissolution in HNO3. The tin dissolution in sulphuric acid occurred through an intermediate of (SnHSO4OH) species. 

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