铝电解NiFe2O4基金属陶瓷惰性阳极电解过程表面结构特征演变规律

The new aluminum reduction technology based on inert electrode was received much concern because of the green-house gas elimination. The key to realize this technique is the corrosion rate of inert anode during electrolysis. During a 20kA pilot testing of this technology, a new phenomenon, which is different from previous understanding about the corrosion mechanism of NiFe2O4 based cermet inert anode,was observed.That is to say, because of the effect of the electrolyte, or the nascent state oxygen, or the both together, the phase at the surface of inert anode would transform and form an aluminum-rich compact layer, which the anti-corrosion performance is stronger than its matrix. And at the same time, the compact layer could decrease effectively the corrosion rate of the inert anode. This project would carry out the research on the evolution of the surface structure of NiFe2O4 based cermet inert anode for aluminium reduction during electrolysis porcess. The mechanisms of the formation and the erosion of new produced phase at the surface of NiFe2O4 based cermet inert anode polarized are discovered. And the kinetic characeteristics of the growth and the corrosion in-situ of the compact anti-corrosion layer, which is made of new producted phase, are also illuminated. And then, a controlling method would be founded, which would realize the continuous maintain of this compact anti-corrosion layer. Thus, a theoretical basis of anti-corrosion techology, which bases on the formation of the compact anti-corrosion layer in-situ at the material surface, would be provided. Simultaneously, a referance would also be provided for the development of material anti-corrosion technology under various changeable service condition.

基于惰性电极铝电解新工艺因可彻底消除温室气体排放而备受关注。惰性阳极腐蚀速率是其成功的关键。申请者在参与20kA惰性电极试验时发现与以往对NiFe2O4基金属陶瓷腐蚀认识不一致的现象：阳极表面在电解质、或新生态氧、或两者共同作用下发生物相结构转变，而原位生成具有更强耐腐蚀性能的富铝致密层，有效减缓阳极腐蚀。 本项目拟开展"铝电解NiFe2O4基金属陶瓷惰性阳极电解过程表面结构特征演变规律"的研究，揭示极化状态下NiFe2O4基金属陶瓷阳极表面新生物相的生成与腐蚀机理，阐明由新生物相形成的致密耐蚀层原位生长与腐蚀过程的动力学特征，获得阳极表面新生物相形成的致密耐蚀层持续保持的调控方法，为创建基于阳极表面致密耐蚀层原位形成的腐蚀抑制技术提供理论基础。该项目的研究，也可为其他复杂多变服役环境下，材料腐蚀机理的认识以及防腐蚀技术的开发提供借鉴。

铝电解工业是世界各国十分关注的重要基础材料产业，我国是全球最大的原铝生产国与消费国。迅猛发展的电解铝工业面临巨大的减排与节能压力，高效、节能与清洁铝冶金新工艺、新技术与新装备已成为我国铝工业可持续发展的基础与关键。基于惰性电极铝电解新工艺因可彻底消除温室气体排放，实现铝电解工艺的彻底变革而备受关注。. 本项目针对NiFe2O4基金属陶瓷惰性阳极在电解过程表面生成致密耐蚀层的特点，提出开发基于阳极表面由新生物相原位形成致密耐蚀层的腐蚀抑制技术，运用熔盐电化学、冶金热力学与动力学、熔盐物理化学和材料学等理论与原理，重点研究了：（1）NiFe2O4基金属陶瓷组元在Na3AlF6-AlF3-Al2O3熔体中反应的热力学分析；（2）非极化状态下惰性阳极外层物相结构变化；（3）电解条件下惰性阳极外层物相结构变化；（4）电解条件下阳极新生物相的化学腐蚀；（5）NiFe2O4基金属陶瓷惰性阳极外层结构随电解时间的变化；（6）电解温度对NiFe2O4基金属陶瓷惰性阳极结构变化的影响；（7）电流密度对NiFe2O4基金属陶瓷惰性阳极结构变化的影响；（8）氧化铝浓度对NiFe2O4基金属陶瓷惰性阳极结构变化的影响。. 通过对上述内容研究所获得的结果表明：（1）电解条件下，NiFe2O4基金属陶瓷惰性阳极表面金属相Ni在新生态氧及熔体中Al2O3作用下可以形成具有更高致密度的NiAl2O4；有利于降低阳极的腐蚀速率；（2）NiO的添加有利于形成更致密、结合力更好的耐蚀膜层；（3）电流密度对NiFe2O4基金属陶瓷惰性阳极电解过程中表面新生物相NiAl2O4和NiFe2O4的生成影响最大，Al2O3浓度的影响其次，电解温度最小。在一定条件下可获得表面稳定的致密层，有利于提高阳极抗腐蚀能力。