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中国腐蚀与防护学报  2017, Vol. 37 Issue (3): 279-286    DOI: 10.11902/1005.4537.2016.023
  本期目录 | 过刊浏览 |
7020铝合金在3.5%NaCl溶液中的点蚀行为
戴芸1,2,3,刘胜胆1,2,3(),邓运来1,2,3,张新明1,2,3
1 中南大学材料科学与工程学院 长沙 410083
2 中南大学 有色金属材料科学与工程教育部重点实验室 长沙 410083
3 中南大学 有色金属先进结构材料与制造协同创新中心 长沙 410083
Pitting Corrosion of 7020 Aluminum Alloy in 3.5%NaCl Solution
Yun DAI1,2,3,Shengdan LIU1,2,3(),Yunlai DENG1,2,3,Xinming ZHANG1,2,3
1 School of Materials Science and Engineering, Central South University, Changsha 410083, China
2 Key Laboratory of Nonferrous Materials Science and Engineering, Ministry of Education, Central South University, Changsha 410083, China
3 Nonferrous Metal Oriented Advanced Structural Materials and Manufacturing Cooperative Innovation Centre, Changsha 410083, China
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摘要: 

采用浸泡实验与电化学循环极化曲线测试研究了7020铝合金在3.5% (质量分数) NaCl溶液中的点蚀行为,并结合金相显微镜 (OM)、扫描电镜 (SEM) 及扫描透射电镜 (STEM) 的微观组织观察结果对相关机理进行了分析和探讨。结果表明:7020铝合金的最大点蚀深度随时间变化的曲线为S型,呈缓慢增长-快速增长-保持稳定的过程。合金中α-AlFeSiMn相在点蚀浸泡过程中充当阴极,且发生了去合金化,周围的Al基体充当阳极而被腐蚀,含MnCr的弥散相则伴随Al基体的腐蚀而脱落。浸泡后期点蚀敏感性降低,表面的腐蚀产物可起到一定的保护作用。

关键词 7020铝合金点蚀腐蚀动力学第二相循环极化曲线    
Abstract

The pitting corrosion behavior of 7020 aluminum alloy in 3.5%(mass fraction) NaCl solution was investigated by immersion test and cyclic polarization curve, while the corrosion morphology of the alloy was characterized by means of optical microscopy (OM), scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM). The results show that the curve of maximum depth of corrosion pits versus time exhibits ''S''-like shape. α-AlFeSiMn phase may act as a local cathode, thereby de-alloying occurred around particles of α-AlFeSiMn phase, i.e. Al matrix nearby the particles of α-AlFeSiMn phase was dissolved due to its anode nature, while Mn-and Cr-containing precipitates in the matrix may fall off along with the dissolved Al. Pitting susceptibility reduces in the later stage of corrosion due to that the formed corrosion products may act as a protective barrier for the alloy to some extent.

Key words7020 aluminum alloy    pitting corrosion    corrosion dynamics    second phase    cyclicpolarization curve
收稿日期: 2016-02-04     
基金资助:国家重点研发计划 (2016YFB0300901) 和中南大学“升华育英计划” (2012年)

引用本文:

戴芸,刘胜胆,邓运来,张新明. 7020铝合金在3.5%NaCl溶液中的点蚀行为[J]. 中国腐蚀与防护学报, 2017, 37(3): 279-286.
Yun DAI, Shengdan LIU, Yunlai DENG, Xinming ZHANG. Pitting Corrosion of 7020 Aluminum Alloy in 3.5%NaCl Solution. Journal of Chinese Society for Corrosion and protection, 2017, 37(3): 279-286.

链接本文:

https://www.jcscp.org/CN/10.11902/1005.4537.2016.023      或      https://www.jcscp.org/CN/Y2017/V37/I3/279

图1  7020铝合金的SEM像和第二相EDS分析结果
图2  7020铝合金的HADDF像及弥散相EDS分析结果
图3  7020铝合金浸泡不同时间后截面最大腐蚀深度
图4  7020铝合金浸泡1176 h后的截面SEM像
图5  以最大点蚀深度d表征的腐蚀动力学图
图6  7020铝合金浸泡不同时间后的SEM像
图7  7020铝合金浸泡不同时间后的SEM像和EDS分析结果
Time / h O Al Si Fe Mn
0 --- 68.73~85.74 4.60~5.43 16.39~20.90 3.93~4.19
168 6.71~8.19 55.02~61.11 5.23~6.14 14.75~19.28 3.23~3.41
1176 10.10~17.13 47.42~49.75 3.09~4.47 11.43~13.25 2.64~3.29
表1  7020铝合金在不同浸泡时间后第二相的化学成分
图8  7020铝合金浸泡不同时间后的极化曲线
Timeh EcorrmV EpitmV ErpmV |Epit-Erp|mV IcorrμAcm-2
0 -647 -572 -527 50 0.74
168 -967 -596 -546 50 15.60
504 -922 -622 -577 45 2.16
840 -974 -689 -663 26 137.00
1176 -1122 -642 -534 108 104.00
表2  7020铝合金浸泡不同时间后的极化曲线特征参数
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