5052和6061铝合金在中国南海深海环境下的腐蚀行为研究

CORROSION BEHAVIOR OF 5052 AND 6061 ALUMINUM ALLOYS IN DEEP OCEAN ENVIRONMENT OF SOUTH CHINA SEA

通过实海暴露实验,研究了5052和6061铝合金在中国南海海域800和1200 m深海环境下浸泡3 a的腐蚀行为.采用SEM,EDS和XRD技术,分别进行了腐蚀形貌观察、腐蚀产物成分和相组成分析.结果表明:2种铝合金在深海环境下均发生了很严重的局部腐蚀,表面形成了白色的腐蚀产物,腐蚀产物由Al_2O_3,SiO_2,以及少量Mg_3(SO_4)_2(OH)_2和NaCl组成.5052和6061铝合金均在铆接区域产生了缝隙腐蚀穿孔,其中,5052铝合金还在截面形成了沟槽状腐蚀坑.在样品主表面,5052和6061铝合金主要发生点腐蚀,其中6061铝合金表面的点蚀坑深度更大,密度更高,且在800 m深海环境下发生了点蚀穿孔.分析表明,随着水深的增加,5052和6061铝合金的最大点蚀坑深度先增加后降低,最大点蚀坑深度的最大值出现在水深800 m左右.这是由于800 m深海中的溶氧量最低,促进了局部腐蚀的发生.

Aluminum alloys have been found ever-increasing applications in marine environ- ments. The study on the corrosion of aliminum alloys using field test was started in USA in 1940s. Such studies, however, were carried out in China untill 1980s. Although the corrosion behaviours of 11 kinds of aluminum alloys were investigated exposed to tide, splash and full immersion zones at Qingdao, Zhoushan, Yulin and Xiamen area of China, the corrosion behaviour of materials in deep ocean environments is different from that in shallow marine environments. In this work, the corrosion behavior of 5052 and 6061 aluminum alloys in 800 and 1200 m deep ocean environments of South China Sea was studied using field test. The morphology and composition of corrosion products were investigated using SEM, EDS and XRD. The results indicated that severe local corrosion took place in the aluminum alloys. The corrosion products were composed of A1203, SiO2 and a small amount of Mg3（SO4）2（OH）2 and NaC1. The crevice corrosion perforation occurred on the edge of 5052 and 6061 samples. And the groove corrosion pits formed on the cross section of 5052 sample. Pitting corrosion took place on the main area of 5052 and 6061 samples. The size and density of pits formed on 6061 aluminum alloy were higher than those on 5052 aluminum alloy. And the pitting corrosion perforation formed on 6061 aluminum alloy in 800 m deep ocean. Comparing with the data of literatures, the maximum pit depths of 5052 and 6061 aluminum alloys decreased first and then increased with depthincreased. The maximum value of pit depth appeared at about 800 m deep ocean. This is due to the amount of dissolved oxygen is the lowest in 800 m deep ocean, which promotes local corrosion.