Collect. Czech. Chem. Commun. 1993, 58, 2013-2020

Corrosion and Passivation of Tin Anode in Na2CO3 Solutions and the Effect of Halide Ions

Sayed S. Abd El-Rehima, Fouad Tahab, Mohamed B. Salehb and Said A. Mohamedb

a Chemistry Department, Faculty of Science, Ain Shams University, Cairo, Egypt
b Chemistry Department, Faculty of Science, Minia University, Minia, Egypt


The corrosion and passivation of tin anode in Na2CO3 (0.01 to 1.0 M) was investigated using potentiodynamic and cyclic voltammetry techniques and complemented by X-ray and scanning electron microscopy. The polarization curves exhibit two anodic peaks assigned to the electroformation of Sn(II) and Sn(IV) species, respectively, prior to permanent pssive region. The anodic dissolution reactions are controlled by diffusion. X-Ray diffraction showed that the permanent passive layer is duplex and consists of SnO and SnO2. A multiplicity of cathodic peaks is related to the electroconduction of the anodically formed compounds. Addition of Cl-, Br- or I- ions into the carbonate solutions enhances the anodic dissolution of tin to some extent depending upon the sodium carbonate concentration. In the passive region, addition of the halide ions causes pitting of the halide ions causes pitting corrosion at a critical pitting potential. The pitting potential decreases with increasing both the halide ion concentration and the scanning rate but increases with increasing the sodium carbonate concentration. SEM examination confirms the occurance of pitting corrosion.