2024-T351铝合金在酸性NaCl溶液中SCC行为的电化学噪声检测

 采用电化学噪声技术对2024-T351铝合金在酸性NaCl溶液中的应力腐蚀开裂过程进行检测,并通过对电流噪声信号进行时域和频域分析,研究裂纹尖端腐蚀行为以及裂纹萌生和扩展过程的电化学噪声特征,并得出裂纹扩展的判断依据。结果表明,在浸泡初期,电流噪声时频谱中的振幅较小,能量主要集中于高频段,表明电极表面主要发生了膜破裂-再钝化等快反应过程,裂纹处于萌生阶段。随着浸泡时间的增加,电流噪声中出现特征峰。此时,低频段能量逐渐增加,表明裂纹进入扩展阶段。通过对电流噪声信号进行小波分解,可以区分应力腐蚀开裂过程中裂纹萌生和扩展的不同阶段。

Electrochemical Noise Detection for SCC Behavior for 2024-T351 Aluminium Alloy in Acid NaCl Solution

The stress corrosion cracking (SCC) behavior of 2024-T351 aluminium alloy in acid NaCl solution was studied by using the electrochemical noise technique. The electrochemical noise signal was recorded during the immersion test of the Wedge Opening Loading (WOL) specimen in the Zero Resistance Ammeter (ZRA) mode. The characteristic parameters were analyzed in time and frequency domains, respectively. The results indicate that SCC process of AA2024-T351 is not continuous. The current noise could be used to analyze the nucleation and propagation processes of SCC. During the nucleation period of SCC, the transient peaks could be observed, which was characterized by the small fluctuation amplitude of the current noise. This implies that the alternating film rupture and re-passivation process is dominant on the specimen surface. With the immersion time increasing, the characteristic peaks are observed. It is indicated that the crack propagation occurs. Meanwhile, the amplitude of the characteristic peaks increases and the periodic character could also be observed. The wavelet decomposition provides a strong tool to distinguish the nucleation and propagation processes of SCC according to the different current energy distribution.