Abstract: Specimens stressed at yieiding point in acidic occluded solutions were tested to simulate the mechanical and environmental states within stress corrosion cracks for "1Cr13 steel /0.5mol/L Cl-" system, and to determine the corrosion rates as well as the electrochemical behaviour of crack tips at different propagating stages. The experimental potential / pH diagrams depicting kinetic and thermodynamic behaviours inside cracks as well as mechanical and environmental effects on occluded cell corrosion were constructed. A critical pH value (about 4.1 at 90℃) was found from the "corrosion rate/pH" curve, "potential / time" curves, and potential / pH diagrams, below which passive-active transition occurred at crack tips and corrosion rate increased rapidly. Both stress and acidification caused a higher corrosion rate and a greater critical pH value.

摘要： 模拟1Cr13不锈钢在0.5mol/L NaCl溶液中应力腐蚀裂缝尖端的环境变化和受力状态,进行腐蚀及电化学测试,绘制了描述该体系应力腐蚀裂缝内各阶段热力学和动力学行为的实验电位～pH图.腐蚀率～pH曲线、电位～时间曲线和电位～pH图等均表明上述体系应力腐蚀裂缝内存在1个临界pH值(90℃时约为4.1).低于临界值,裂缝尖端发生钝态向活态的转变,腐蚀速度骤增,电位下降.应力和微区酸化都使裂缝内的钝化效果变差,腐蚀率增大.应力使裂缝尖端开始加速腐蚀的临界pH值升高.