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Corrosion behaviour of Tin in citric acid solutions and effect of some inorganic and organic compounds

E.E.Foad El Sherbini, E.Hamed

The electrochemical Behaviour and corrosion of tin in various concentrations of citric acid solutions (0.1 to 1.0M) has been studied by using cyclic voltametric technique under different experimental conditions. The potentiodynamic anodic polarization curves exhibit active/passive transition. The active dissolution of tin involves one anodic peak. During the active region, tin dissolves as Sn(II), which is oxidized to Sn(IV) to yield either Sn(OH)4 or SnO2 on the anode surface. The active dissolution of tin enhances with increasing acid concentration, temperature and scan rate. The cathodic curve exhibits one cathodic peak corresponding to the reduction of passive layer.Addition of Cl-, Br- or I- ions to the citric acid solution enhances the anodic dissolution of tin. The aggressiveness of the halide ions towards the stability of the passive film decreases in the order Cl->Br- >I-.Addition of some polyethylene glycols to citric acid solution decreases the current density of the anodic peak and shifts its peak potential towards the negative direction. These changes depend on the concentration and molecular weight of the polyethylene glycol added.