Effect of Some Factors on the Behavior of Galvanic Couple of Magnetite and Iron in Aqueous Solutions

In this study, the effect of some factors on the behavior of the galvanic couples between magnetite and iron, were investigated in aqueous solutions containing EDTA and ferrous ion; in which magnetite dissolved reductively. Different ratios between iron areas to magnetite area were studied. The experiments simulate the case of magnetite film partially removed from iron surfaces in the course of chemical cleaning when coupling conditions occur with variable area ratios with time. The effect of ferrous ion concentration, EDTA concentration, solution pH and temperature were studied. The couple potential and individual currents of magnetite and iron were used, which revealed that the reductive dissolution of magnetite increase with either pH decrease or temperature increase. At [EDTA] = 0.02M, and when [Fe2+] increase in the solution, the rate of magnetite dissolution increases. On the other hand, at [Fe2+] = 0.02, the increase in [EDTA] will cause a larger increase in dissolution rate. The effect of pH on the dissolution rate of magnetite and iron was investigated in the range 2.5 – 4.5. Higher current values recorded at pH 2.5 then decreases with the increases in the pH. This effect can be expected from the reductive dissolution equation, which is related with proton concentration. When temperature increases in the range 40oC to 65oC the dissolution rate also increases