Study On The Corrosion Behavior Of Carbon Steel Exposed Under The Electric Field In The Atmospheric Environment

The corrosion of metals in corresponding working environments includes three main typies, atmospheric corrosion, soil corrosion and corrosion in water system, atmospheric corrosion is considered as the most common type. Atmospheric corrosion is caused by the moisture abosorbed on the surface of metals exposed to the atmospheric environment. As a matter of fact, it belongs to the corrosion due to the electrochemical recations. In addition, rain fall could be the reason leading to the corrosion in the presence of electrolyte assembled on the metal surface. Among the electric power industry, most of the metal materials are employed in the electric power transmission system. Electric power transmission tower however corroded seriously in the corresponding working atmospheric environment, which is very different from the characteristics of the general corrosion. In addition, a majority of metal materials working in the electronic devises normally experienced a relatively high corrosion rate. A common feature for these metal materials is that they were both exposed to the environment with electric field. Hence,we believe that the electric field generated around the transmission line acts as another critical factor influencing the atmospheric corrosion of metals.In this study, a self-estabilshed system simulated the practical atmospheric environment was employed to investigate the atmospheric corrosion of metal exposed under the electric field. The weight gain, electrochemical tests and characterision ofcorrosion products were also employed to futher study the atmospheric corrosion behavior of the steel exposed to DC electric field and the effects of DC electric field on the corrosion products formed on the steel. The main results obtained on the basis of the experiments were draw as follows:(1) The effects of the DC electric field on the atmospheric corrosion of the steel exposed to the simulated wet-dry cyclic process were investigated through the weight gain, electrochemical experiments and characterization of the corrosion products. The results show that the corrosion rate of steel increased during the initial exposure and then dropped slightly to the relatively stable value. The existence of the DC electric field accelerates the corrosion of the steel in atmospheric environment. The higher the intensity of the DC electric field, the greater value is the corrosion rate.(2) The effects of the DC electric field on the corrosion behavior and corrosion products of steel exposed to the simulated industrial and marine atmospheric environments were studied by means of weight loss, electrochemical tests and characterization of corrosion products. The results show that the DC electric field gives no rise to the corrosion kinetic of the steel. The existence of the DC electric field enhances the growth of the instable γ-FeOOH, as well as inhibits the transformation of γ-Fe OOH to the dense α-FeOOH. All those lead to decrease the protective ability of the rust layer formed on the steel, as a result of accelerating the steel corrosion.