应力应变下TC2钛合金在模拟海水环境中的腐蚀行为

目的研究TC2钛合金在模拟海水中的表面电化学及腐蚀行为,以及不同形变对其的影响。方法制备U形试样,进行模拟海水浸泡试验,采用电位测试、交流阻抗及极化曲线测试、扫描电镜(SEM)、X射线衍射(XRD)等方法进行分析。结果在240 d模拟海水中浸泡试验期间,无形变TC2钛合金表面钝化膜阻抗值随时间延长,先迅速增加,后缓慢增加,腐蚀电位持续升高,因此其表面电化学反应下降,腐蚀速率较低。45°形变TC2钛合金试样的表面钝化膜阻抗值先略微上升,后下降,最终低于初始阻抗值。90°形变试样的表面钝化膜阻抗值持续下降。经过240d浸泡后,无形变的试样表面出现微小的点蚀,45°形变试样表面点蚀密度增加,90°形变试样表面垂直压应力方向出现裂纹。XRD结果显示,形变处Ca~(2+)、Mg~(2+)等离子的吸附增加,这可能与表面粗糙度增大,TC2钛合金表面活性增加有关。结论在模拟海水环境中,无应变试样耐腐蚀性较强,应变导致TC2钛合金表面钝化膜破裂,点蚀增加,甚至出现裂纹,增加了TC2钛合金的应力腐蚀敏感性。

Corrosion Behavior of TC2 Titanium Alloy under Strain-stress in Simulated Seawater

The work aims to study the electrochemical and corrosion behavior of TC2 titanium alloy in simulated seawater and the effect of deformation. U-shaped sample was prepared and simulated seawater immersion test was conducted. Potential test, polarization curve test, electrochemical impedance spectroscopy, SEM and XRD were employed for analysis. During 240 d im-mersion test in simulated seawater, the impedance value of non-shaped sample surface passive film rapidly increased initially and then slowly increased as time prolonged, and the corrosion potential continued to increase, so the surface electrochemical reaction decreased and the corrosion rate was low. The impedance value of 45° deformation sample surface passive film initially increased slightly and then decreased and finally dropped below the initial impedance values. The impedance value of 90° deformation sample surface passive film steady declined during test period. After 240 d immersion test, minor pitting appeared on non-shaped sample surface, the pitting density of 45° deformation sample surface increased, and 90° deformation sample surface had cracks perpendicular to the direction of stress. XRD results showed that the adsorption of Ca2+ and Mg2+ ion increased at the deformation, which may be related to the surface roughness and surface activity of TC2 titanium alloy increase. In simulated seawater, the non-shaped TC2 titanium alloy has strong anti-corrosion properties and strain causes breakage, pitting and even cracks on passive film of TC2 titanium alloy, thus increasing stress corrosion sensitivity of TC2 titanium alloy.