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使用通过杠杆系统可以加载的模拟闭塞电池,研究了低碳钢在NO_3~-溶液中缝隙或裂缝内化学和电化学状态的变化。本体系存在一个破裂临界电位区。当外加阳极极化时,闭塞区内溶液pH值下降变酸性,而闭塞区电位维持在腐蚀电位附近。应力对电位和pH位变化的影响不明显。但是,在应力为0.85σ_y时,闭塞区试件发生破裂。金相分析表明,在整个破碎晶粒的外表面发生了晶间腐蚀。应力的作用是使晶粒撕裂,从而使裂缝沿着与应力垂直的晶界方向扩展。
Using the simulated occluded cells that can be loaded by the lever system, the changes of the chemical and electrochemical states of the low carbon steel in the cracks or crevices of NO_3 ~ - solution were investigated. The system has a rupture threshold potential region. When anodic polarization was applied, the pH value of the solution in the occluded region became acidic while the occluded region potential was maintained near the corrosive potential. The effect of stress on the potential and pH changes is not obvious. However, at the stress of 0.85σ_y, the specimen in the occlusion zone ruptured. Metallographic analysis showed that intergranular corrosion occurred on the entire surface of the crushed grains. The role of stress is to tear the grain so that the crack grows along the grain boundary perpendicular to the stress.