Study Of Alternating Stray Current On Corrosion Of Q235 Steel In A Simulated Acid Soil Solution

With more and more buried pipelines, electrified railway lines and high voltage transmissions, stray current happens here and there. Meanwhile, the strong corrosive acidic soil,the different rules change of the alternative current and inconsistency of alternating frequency make people not completely know law of stray current corrosion and build reasonable model of AC stray current. Therefore, it is very difficult for researchers to predict, evaluate and protect the stray current corrosion. According to these problems, this paper uses the Q235 steel in simulated acidic corrosion as the research object. Electrochemical test, weight loss method, the morphology analysis, cyclic voltammetry curve analysis are used to study the rule of AC stray current of Q235 steel in simulated acidic soil solution. Results show that:(1) AC stray current accelerates the corrosion of Q235 steel in acid soil. In simulated acid soil solution, the AC frequency makes the corrosion of Q235 steel change exponentially with the applied unchanged voltage. When the voltage is constant, the higher the AC frequency is,the less the acceleration effect of AC stray current on corrosion is, and the lower the frequency is, the greater the acceleration is;(2) In the case of constant frequency, the corrosion rate increases with the addition of AC voltage. The greater the applied voltage is, the more serious the corrosion of Q235 steel is, and the linear relationship between the applied AC potential and the corrosion rate is v=0.045+0.273?;(3) AC voltage makes an opposite deviation to the corrosion voltage of Q235 steel, and positive and negative potential sweep process is opposite. Specifically speaking, while the potential is positive sweeping and the AC voltage increase, the corrosion potential of Q235 steel is negative offset. And when the potential is negative sweeping, the corrosion potential of Q235 steel is positive offset;(4) The reaction of Q235 steel electrode surface under an AC cycle is divided into three stages: ?: anode active dissolution stage; ?: hydrogen evolution polarization stage; ?: hydrogen evolution control stage. During the hydrogen evolution reaction stage, although material loss caused by AC stray current is smaller than the DC stray current under the same conditions; the hydrogen produced by the hydrogen evolution reaction makes the material prone to hydrogen embrittlement. Therefore, the corrosion is more serious;(5) A strong polarization platform emerges near zero current at low frequencies, and electrochemical polarization dominates the electrode. The platform disappears when the frequency is higher, because external current is the main factor, then, electrochemical polarization current is ignored. The platform appears earlier no matter how the current changes,namely, the two platforms not appear consistently in a cycle. The greater the external potential is, the greater the difference between the two platforms is, moreover, the frequency of the platform is less than 1Hz.