电极极化对铝合金应力腐蚀断裂敏感性的影响

Effect of Electrode Polarization on Stress Corrosion Cracking of 7075 Aluminum Alloys

为了探讨极化对铝合金应力腐蚀断裂 (SCC)敏感性的影响,采用慢应变速率拉伸技术研究了不同恒电位极化条件下 7075T6, 7075T7351, 7075RRA铝合金的应力腐蚀行为。结果表明,在-1 200^-735mV(vsSCE)电位范围内,无论是阳极极化还是阴极极化,甚至弱极化,都会增加7075铝合金在 3. 5% NaCl溶液中的应力腐蚀断裂敏感性,无论哪一种热处理状态的 7075铝合金在极化电位下的ISSRT均明显高于腐蚀电位下的ISSRT。同时,有阴极极化时ISSRT值随电极极化增强而减小,阳极极化时ISSRT值有随电极极化增强而增大的趋势。但不同热处理状态的 7075铝合金受极化电位的影响程度不同。由此认为,阳极溶解和氢效应都是导致 7075铝合金应力腐蚀开裂的重要因素,电化学保护方法并不适用于 7075铝合金应力腐蚀断裂的防护。

The stress corrosion cracking (SCC) behaviors of various heat treated 7075 aluminum alloys at various polarization potentials were studied using slow strain rate tension (SSRT) method. It was found that the SCC susceptibility of 7075 Al alloy in 3.5% NaCl solution increased in the presence of anodic and cathodic polarization or even weak polarization, within the electric potential range from (-1),200 mV to -735 mV (vs. SCE). The intensity of SSRT of 7075 Al alloy in the presence of polarization potential was much larger than that in the presence of corrosion potential, and it decreased with increasing cathodic polarization potential but increased with increasing anodic polarization potential. Moreover, the effect extent of the polarization potential on the SCC of 7075 Al alloy varied with varying heat treatment states. It was suggested not to use electrochemical method to get rid of SCC of the 7075 Al alloy, because both the anodic dissolution and hydrogen effect play important roles in the SCC of the Al alloy.