海水中带锈Q235钢腐蚀电化学参数测定

利用失重法和电化学方法对在海水中浸泡不同时间的Q235钢电极的腐蚀行为和腐蚀速率规律进行了研究。结果表明，对于长期浸泡的Q235钢电极，失重法和电化学方法得到的腐蚀速率结果存在很大差异。利用XRD测定了长期浸泡后锈层成分的变化，发现长期浸泡Q235钢电极锈层中的电化学活性成分β-FeOOH在测试过程中发生还原反应，导致利用电化学方法测得的Q235钢腐蚀速率大于失重法的结果，并且随浸泡时间的延长，这一偏差增大。对长期浸泡Q235钢电极进行电流密度为-25 μA/cm²阴极恒电流预极化处理后发现，随着浸泡时间的延长极化时间也延长，同时，经过预处理之后的Q235钢电极电化学方法测得的腐蚀速率与失重法的结果具有一致的变化规律，表明施加合适的阴极极化预处理能够减小电化学方法与失重法测试结果的偏差。

Corrosion Electrochemical Parameters Test of Rusted Carbon Steel in Seawater

As it is known that the existence of a rust scale on a steel surface may complicate the electrochemical corrosion process of the steel, thereby it is difficult to accurately measure the corrosion rate of carbon steel by traditional electrochemical methods. In this paper, weight-loss method and different electrochemical tests such as polarization curves (PC), electrochemical impedance spectra (EIS) and linear polarization resistance (LPR) were used to study the corrosion behavior of the Q235 carbon steel immersed in seawater for 1 a. The results show that the corrosion rates measured by both the electrochemical and weight-loss measurement show the same degressive trends during a short immersion period (for about 8 weeks), while those measured by electrochemical measurement turn to increase after 8 weeks' immersion in seawater. The longer the immersion time is, the bigger the deviation occurs for the corrosion rates measured by the two kind methods. It is believed that the rust scale presented on the electrodes had a great influence on its corrosion behavior. The evolution of phase constituents of the corrosion products on the rust steel was characterized by XRD. There is an obvious increasing of β-FeOOH in the corrosion product accumulated on the carbon steel with the immersing time going, and the reductive reaction of β-FeOOH during the electrochemical test process leads an overestimate of the corrosion rate, which caused the deviation between weight loss method and electrochemical tests. In order to solve this problem, the electrode was pretreated by a cathodic galvanostatic polarization with current density of -25 μAcm^-2 to counteract the reduction current during the electrochemical test process. After the pre-polarization, the electrochemical measurement results coincided well with weight loss, which means this pre-polarization showed a good calibration of the deviation between the two measurement methods.