TC4在液体推进剂单推-3中电化学腐蚀机理研究

Electrochemical Corrosion Mechanism of TC4 in Liquid Propellant DT-3

关键词:  电化学腐蚀  钛合金  液体推进剂  钝化膜  点蚀电位

Key words:  Electrochemical corrosion  Titanium alloy  Liquid propellant  Passive film  Pitting potential

摘要:

为了开发推进剂/金属材料电化学加速试验技术，需要掌握材料的腐蚀特性。本文采用电化学测试方法，结合扫描电镜（SEM）、光电子能谱（XPS）分析手段，研究了钛合金TC4在液体推进剂单推-3中的电化学腐蚀行为与机理。结果表明：TC4在单推-3中的自腐蚀电流密度约为95nA/cm²，腐蚀速率约为0.8μm/a，抗均匀腐蚀性能良好，TC4在单推-3中可长期使用；TC4在单推-3中具有两段不同的钝化电位区间，随着极化电位的正移，最终形成外层为TiO₂薄膜、中间Al₂O₃阻挡层、内层为TiO+Ti₂O₃的三层结构特征的钝化膜，并具有很正的点蚀电位；单推-3中主要组分肼和硝酸肼对TC4钝化膜的破裂溶解过程具有协同作用。

Abstract:

In order to develop electrochemistry accelerated testing technology for propellant/metal materials， it is necessary to master the corrosion characteristics of materials in the propellants. The electrochemical corrosion behaviour and mechanism of titanium alloy TC4 in liquid propellant DT-3 were studied by electrochemical test and scanning electron microscopy （SEM） and photoelectron spectroscopy （XPS）. The results show that the corrosion current density of TC4 in DT-3 is about 95nA/cm² and the corrosion rate is about 0.8μm/a， which indicates that TC4 has good uniform corrosion resistance and long lifetime in DT-3. It also shows that there are two different potential intervals for passivation of TC4 in DT-3. With the positive shift of potential， a three-layer characteristic passive film is finally formed with TiO₂ film as the outer layer and Al₂O₃ as the middle barrier layer and TiO+Ti₂O₃ as the inner layer while it has a very positive pitting potential. Hydrazine and hydrazine nitrate， the main components of DT-3， have a synergistic effect on the rupture and dissolution process of passive film of TC4.