镁合金表面高温氧化膜CO_(2)矿化处理研究

Research on CO_(2)Mineralization of High Temperature Oxide Film on Magnesium Alloy Surface

为改善镁合表面高温氧化膜性能,采用CO_(2)矿化技术对AZ80-0.38Nd(质量分数/%,下同)合金表面高温氧化膜进行了处理。对比考察了合金氧化膜CO_(2)矿化处理前后的微观形貌、结构及物相,并采用浸泡和电化学测试技术研究了膜层的腐蚀防护性能。结果表明,AZ80-0.38Nd合金表面高温氧化膜具有典型的裂纹与孔洞缺陷,CO_(2)矿化处理很好地修复了合金表面高温氧化膜缺陷,提高了氧化膜层的致密度,并在合金表面构筑由棒状MgCO_(3)·3H_(2)O和层片状4MgCO_(3)·Mg(OH)2·4H 2O组成的矿化膜。相比于氧化膜,矿化膜可将合金自腐蚀电位(E corr)由-1.41 V SCE提高至-1.33 V SCE,将合金自腐蚀电流密度(i corr)由1.62×10^(-4)A/cm^(2)减小至2.47×10^(-5)A/cm^(2)。此外,矿化膜还能将合金局部腐蚀转变为均匀腐蚀,呈现优异的腐蚀防护性能。

The high temperature oxide film of the AZ80-0.38Nd(wt%)alloy was mineralized with CO_(2)to improve its property.The morphology,microstructure and composition of the oxide film before and after CO_(2)mineralization were observed and analyzed.The corrosion protection performance of the oxide film before and after CO_(2)mineralization were investigated by immersion and electrochemical tests.The results showed that cracks and holes appeared on the high temperature oxide film of AZ80-0.38Nd alloy.While CO_(2)mineralization treatment could eliminate cracks and holes,resulting in densification of the oxide film.The mineralized film consisted of rod-like MgCO_(3)·3H_(2)O and lamellar 4MgCO_(3)·Mg(OH)2·4H 2O was constructed on the oxide film.Besides,compared with the oxide film,the mineralized film increased the corrosion potential(E corr)of the alloy from-1.41 V SCE to-1.33 V SCE,and reduced the corrosion current density(i corr)of the alloy from 1.62×10^(-4)A/cm^(2)tO_(2).47×10^(-5)A/cm^(2).In addition,the mineralized film can also transform the local corrosion of the alloy into uniform corrosion,showing excellent corrosion protection performance.