Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy
Influence of chloride ion concentration on the electrochemical corrosion behaviour of plasma electrolytic oxidation coated AM50 magnesium alloy
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DOI：
10.1016/j.electacta.2010.05.087
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发表时间：
2010-09-01
影响因子：
6.6
通讯作者：
Dietzel, W.
中科院分区：
文献类型：
--
作者：
Liang, J.;Srinivasan, P. Bala;Dietzel, W.
采用动电位极化和电化学阻抗谱（EIS）研究了脉冲直流电源下AM 50镁合金表面的硅酸盐和磷酸盐等离子体电解氧化（PEO）涂层在不同氯离子浓度的NaCl溶液中的电化学降解，0.01 M、0.1 M、0.5 M和1 M。通过光学显微镜和扫描电子显微镜检查50小时的浸泡/EIS测试后的PEO涂覆的试样的表面。结果表明，氯离子浓度对PEO涂层镁合金在NaCl溶液中的腐蚀性能有显著影响。发现硅酸盐基涂层在较低氯离子浓度的NaCl溶液（0.01 M和0.1 M NaCl）中比磷酸盐基涂层对镁基材提供上级耐腐蚀性。另一方面，发现这两种PEO涂层对局部损伤高度敏感，并且在含有较高氯化物浓度（0.5M和1 M）的溶液中不能对镁合金基材提供有效的腐蚀保护。在这两种情况下，随着氯化物浓度的增加，观察到局部损伤的程度更大。(c)2010爱思唯尔有限公司版权所有。
The electrochemical degradation of a silicate- and a phosphate-based plasma electrolytic oxidation (PEO) coated AM50 magnesium alloy obtained using a pulsed DC power supply was investigated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in NaCl solutions of different chloride ion concentrations viz., 0.01 M, 0.1 M, 0.5 M and 1 M. The surface of the PEO coated specimens after 50h of immersion/EIS testing was examined by optical microscopy and scanning electron microscopy. The results showed that the corrosion deterioration of PEO coated magnesium alloy in NaCl solutions was significantly influenced by chloride ion concentration. The silicate-based coating was found to offer a superior corrosion resistance to the magnesium substrate than the phosphate-based coatings in lower chloride ion concentration NaCl solutions (0.01 M and 0.1 M NaCl). On the other hand both these PEO coatings were found to be highly susceptible to localized damage, and could not provide an effective corrosion protection to Mg alloy substrate in solutions containing higher chloride concentrations (0.5 M and 1 M). The extent of localized damage was observed to be more with increase in chloride concentration in both the cases. (c) 2010 Elsevier Ltd. All rights reserved.