Effect of Cr(VI) - Fe(II) interaction on the corrosion resistances of iron at different pH in dichromate solutions

摘要

Effect of Cr(VI) - Fe(II) interaction on the corrosion resistance of iron in dichromate solutions has been studied under different experimental conditions.The presence of dissolved oxygen (DO) in the solution decreases Cr(VI) reduction by Fe(II) at pH 4 which became quite noticeable at pH 7.This probably influences corrosion of iron to certain extent.A positive shift of OCP and measurements of a higher charge transfer resistances of iron in dichromate solution of pH 2 and 3 suggest the formation of a protective film on iron.Energy Dispersive X-ray Analysis (EDXA) of iron immersed in Cr(VI) solution indicated a greater involvement of chromium in the formation of a protective film at iron surface.On the other hand,the EDXA analysis showed a decrease in chromium concentration in the reaction product film on the immersed iron surfaces in Cr(VI) solution at pH 4 and above.A shift of OCP in the negative direction and the occurrence of lower charge transfer resistance at the above pH as compared to pH 2 and 3 is attributed to a decrease in the protective properties of the film.