交变应力频率对E690钢在3.5%NaCl溶液中腐蚀电化学行为的影响

采用电化学技术与微观形貌观察,研究了不同频率(0.1,0.5,1.0,1.3,1.8和2.0 Hz)弹性交变应力下E690高强海洋工程用钢在3.5%(质量分数) NaCl溶液中的腐蚀电化学行为,探讨了加载频率对腐蚀反应机理的影响。结果表明,存在一个临界频率,将交变应力作用下腐蚀电化学行为分为两个不同的阶段。加载频率在临界频率以下时,随着弹性交变应力加载频率的增大,E690钢的应变速率峰值增大,钢的表面产生活性位点增多,腐蚀过程主要受活化控制,腐蚀速率和局部腐蚀面积均随着加载频率的提高而增大。加载频率超过临界频率时,腐蚀过程主要受扩散控制,腐蚀速率和局部腐蚀面积不受加载频率变化的影响。

Effect of Alternating Stress Frequency on Corrosion Electrochemical Behavior of E690 Steel in 3.5%NaCl Solution

The corrosion behavior of E690 steel in 3.5%(mass fraction) NaCl solution by applied elastic alternating stresses of different frequencies(0.1, 0.5, 1.0, 1.3, 1.8 and 2.0 Hz) was studied by electrochemical test and surface characterization. Results show that there is a critical loading frequency for the applied alternating stress that divides the corrosion electrochemical behavior into two different regions. When loading frequency is below the critical frequency, the maximum strain rate of E690 steel and the number of active sites on steel surface increases with the increasing loading frequency. The corrosion process is mainly controlled by activation. The corrosion rate and the portion of localized corrosion area increase with the increase of the loading frequency. When loading frequency is higher than the critical frequency, the corrosion process is mainly controlled by diffusion. Hence, the loading frequency has little impact on the corrosion rate and localized corrosion area.