Al-Zn-Sn-Ga合金点蚀行为及扩展机理  

Pitting behavior and mechanism of Al-Zn-Sn-Ga alloy

作　　者：贺俊光[1] 文九巴[1] 周旭东[1] 

机构地区：[1]河南科技大学材料科学与工程学院,河南洛阳471023

出　　处：《材料热处理学报》2013年第8期31-36,共6页Transactions of Materials and Heat Treatment

基　　金：河南省科技创新杰出人才计划(094200510019);河南省自然科学基金项目(092300410132)

摘　　要：通过分析Al-7Zn-0.1Sn-0.015Ga(质量分数,%)合金在3.5%NaCl溶液中的点蚀形貌及电化学阻抗谱(EIS)研究该合金的点蚀行为及扩展机理。结果表明:该合金析出相界面处由于Cl-吸附和微电池的共同作用优先溶解引发点蚀。蚀孔内金属离子浓度增加,Cl-向孔内迁移导致孔内Cl-浓度升高,同时孔内金属离子水解使孔内H+浓度升高,蚀孔迅速纵深发展。随着析出相溶解及孔深增加,腐蚀产物在蚀孔处堆积造成金属离子传质阻力增大,产生浓差极化导致蚀孔底部电位正移,纵向腐蚀速率减慢;回沉积在蚀孔处的Ga和Al形成Ga-Al汞齐,分离氧化膜使铝基体不断溶解,也使腐蚀产物不断脱落,使点蚀坑横向扩展。Pitting behavior and its propagation mechanism of Al-7Zn-0. 1Sn-O. 015Ga （mass%） alloy was investigated by observation of pitting morphology and electrochemical impedance spectroscopy （ EIS）. The results show that pitting occurs at the interface of precipitated phase and ct-A1 matrix preferentially caused by the combined effects of the C1- absorption and the micro-corrosion cell. The pits grow rapidly to the depth at first due to the high concentration of C1- and H＋ within the pits caused by the migration of Cl- and hydrolysis of metal ion. With the dissolution of precipitated phases and increase of the hole depth, the mass transfer resistance of metal ions increases because of the accumulation of corrosion products, resulting in concentration polarization which leads to the positive shift of the potential at the hole bottom, the corrosion rate in vertical slows down. Ga-A1 amalgam separates the oxide film and or-A1 matrix by the redeposition of Ga ion back to around the pits vicinity, making the lateral extension of pits.

关 键 词：铝合金 牺牲阳极 电化学阻抗谱 点蚀行为 点蚀机理 

分 类 号：TG174.41[金属学及工艺—金属表面处理]