Effect of the addition of oxo-anions on the corrosion and passivation of tin in synthetic industrial water

Effect of the addition of oxo-anions MoO42−, SiO42−, HPO42− and HCO3− on the corrosion and passivation of tin in a synthetic medium similar to industrial water has been studied by using electrochemical techniques. The results show that tin manifests a passivation phenomenon with breakdown of passivity. Addition of oxo-anions leads to retard a breakdown of passivation and the inhibition of pitting process of tin. The more marked inhibiting effect is obtained in the presence of MoO42− and SiO42−. The detailed study of the influence of the MoO42− shows that the pitting sensitivity of tin decreases when the molybdate concentration increases in solution. Then, these ions offer a good efficiency even at high temperature and for a chloride concentration up to 0.5 M.