The Study On The Electrochemical Corrosion Characteristics Of A Low-alloy Steel

Electrochemical methods such as potentiodynamic polarization and electrochemical impedance spectroscopy, as well as immersion test, were employed to investigate the influence of temperature and flow velocity on the corrosion behavior of CT80 steel.The results of experiments show: at the temperature range of 20 ℃~ 80 ℃, in the 3.5%Na Cl solution, with the increasing of temperature, The open circuit potential shifted to the negative at first then to the positive. The open circuit potential reaches to the minimum at 60 ℃. The polarization cure results show that the corrosion current density of CT80 increase at first and then decrease with the rising of temperature. The corrosion current density reaches to the maximum with the maximum corrosion rate at 60℃. The result of the electrochemical impedance spectroscopy shows that the Polarization resistance(Rp) decrease at first and then increase as the rising of temperature. The Rp value reaches to the minimum with the maximum corrosion rate. At the range of the flow velocity FV=0~1m/s, as the flow velocity increase, flow of the solution makes open circuit potential and corrosion potential shift to positive direction,corrosion current density increase and polarization resistance of double layer decrease. The increase of flow velocity shorten the time of the open circuit potential reach the stable state. As the flow velocity increase, Flow velocity has the negative effect on the mechanism of anodic reaction in the corrosion process, increase the value of Tafel slope for the cathodic reaction,,the cathode process control the whole corrosion process. The improvement of flow velocity increase the CT80 corrosion current density. Intensified the corrosion process. The Rp value of steel shift to the downward trend with the increase of flow velocity. The Rp value reaches the minimum at flow velocity of 1m/s with the maximum corrosion rate. Under the static corrosion condition, According to the method immersion test, the corrosion rate reach the maximum at 60 ℃. Consistent with electrochemical testing results, the corrosion morphology are all Uniform corrosion. Under the flow corrosion condition, as the flow velocity increase, the corrosion rate of steel Significantly increase, in the flow solution of 1mm/s, the local corrosion occur.