Ca、Mn元素对Mg-Zn系合金在磷酸盐缓冲液中腐蚀行为的影响

Effect of Ca and Mn on Corrosion Behavior of Mg-Zn Alloys in Phosphate Buffer Solution

摘要:

本文采用XRD、SEM、EDS、三维轮廓仪和失重法等手段研究了Mg-6Zn、Mg-6Zn-1Ca和Mg-6Zn-Mn合金在磷酸盐缓冲盐溶液(PBS)中的腐蚀行为,并探讨了三种合金的腐蚀机理。结果表明,添加相同含量的Ca和Mn均能使合金的失重率降低,但添加Mn元素后(浸泡10天时W_r=3.91%)比添加Ca元素后(W_r=6.78%)合金的失重率更低,说明Mn元素更有抗PBS腐蚀能力,这与Mn的加入在合金表面形成致密的氧化膜有关；同时,Mg-6Zn-1Mn合金在浸泡过程中表面存在点蚀现象,经分析是由第二相与基体构成原电池导致。在420 ℃不同保温时间(2~20 h)固溶处理后,合金表面的点腐蚀现象随着保温时间的增加而减弱,表明长时间的固溶处理可以减少第二相与镁基体之间的微电偶腐蚀,增加了合金均匀腐蚀的倾向。

关键词:Mg-Zn合金; 腐蚀行为; 点腐蚀; 第二相; 固溶处理

Abstract:

The corrosion behavior of Mg-6Zn, Mg-6Zn-1Ca and Mg-6Zn-1Mn alloys in Phosphate Buffer Saline (PBS) solution were studied by XRD, SEM, EDS, 3D profilometer and weight loss method, and the corrosion mechanism of the three alloys were discussed. The results show that the addition of Ca and Mn can reduce the weight loss rate of the alloy, but the weight loss rate of the alloy with Mn addition (W_r=3.91 % after immersed for 10 days) is lower than that of the alloy with Ca addition (W_r=6.78 %), indicating that Mn element has better corrosion resistance to PBS, which is related to the formation of dense oxide film on the surface of the alloy with Mn addition. At the same time, Mg-6Zn-1Mn alloy shows that pitting corrosion is caused by the primary battery composed of the second phase and the matrix. After solution treatment at 420 °C for different holding time (2~20 h), the corrosion pit of the alloy surface decreases with the increase of holding time, indicating that long time solution treatment can reduce the galvanic corrosion between the second phase and the magnesium matrix, and increase the tendency of uniform corrosion of the alloy.

Key words:Mg-Zn alloy; corrosion behavior; corrosion pit; second phases; solution treatment