氢氟酸-硝酸体系中Ti-6Al-4V的腐蚀加工溶解特征

Corrosion Processing Dissolution Characteristics of Ti-6Al-4V in Hydrofluoric –Nitric Acid System

摘要:

本文利用E-t曲线、动电位极化曲线研究了氢氟酸-硝酸体系中溶液主体成分、温度对Ti-6Al-4V腐蚀加工溶解行为和特征的影响，通过测试阳极与阴极反应动力学揭示钛合金腐蚀加工动力学规律。研究结果表明，在该溶液体系中钛合金的腐蚀加工是侵蚀-溶解-钝化循环往复的过程，硝酸的钝化作用与氢氟酸的溶解作用同时存在，当钝化膜的生成速度和钛基体的溶解速度达到动态平衡时，腐蚀速度处于相对稳定的状态。腐蚀加工初期阶段氢氟酸浓度会影响钛合金表面氧化膜的破坏，浓度较低时，氧化膜较难破坏，自腐蚀电位正移；浓度较高时，氧化膜容易被腐蚀溶解，自腐蚀电位负移。腐蚀加工速度与氢氟酸浓度和温度有关，氢氟酸浓度和温度增加，反应活化能减少，腐蚀溶解加剧。氢氟酸浓度较低时，温度对加工速度的影响占主导地位；浓度增加到80mL/L，温度的影响减弱，氢氟酸起主要作用。

Abstract:

The effects of main solution ingredients, temperature on dissolution and characteristics of corrosion processing for Ti-6Al-4V in hydrofluoric-nitric acid system were investigated by means of E-t curve, potentiodynamic polarization curve. Moreover anodic and cathodic reaction rate measurements were used to discuss corrosion dynamics. The process of “attack→oxidation→dissolution” repeats continuously during the course of corrosion dissolution of titanium alloy in this solution system. The growth and destruction of passive film simultaneously occur. Corrosion processing rate tends to be stable when the growth of passive film and dissolution of the substrate achieve dynamic balance. At the early stage of corrosion processing, corrosion potential changes to a more positive value when the concentration of hydrofluoric acid is low, indicating that oxide film is difficult to be attacked, while in case of higher concentration, corrosion potential becomes negative quickly as oxide film is easily dissolved. Corrosion dissolution rate is affected by hydrofluoric acid concentration and temperature. With the increase of hydrofluoric acid concentration and temperature, the activation energy declines, corrosion dissolution is enhanced. Temperature plays a leading role under the condition of lower concentration of hydrofluoric acid. When the concentration reaches 80mL/L, the influence of temperature attenuates and the concentration of hydrofluoric acid becomes the major factor.