材料期刊网

目的：提出一种镁合金微弧氧化膜层的退除工艺,提高镁合金的二次利用率。方法以硝酸、氟化钾、柠檬酸、十二烷基苯磺酸钠( SDBS)及缓蚀剂为组分配制退膜液,设计正交试验,以退除速率、表面粗糙度作为评判标准,优化退膜液配方。分析退膜液中各组分的作用,研究退膜过程中退膜量与时间的关系,讨论膜层厚度与腐蚀率、表面粗糙度的关系。采用优化的退膜液对镁合金微弧氧化膜层进行退除,观察表面宏观及微观形貌。结果退膜液各组分针对退膜速率和退膜后镁合金基体表面粗糙度的极差由大到小均依次为：R硝酸>R氟化钾>R柠檬酸>RSDBS>R缓蚀剂。对退膜速率和表面粗糙度影响最大的是硝酸浓度,其次是氟化钾浓度,柠檬酸、SDBS及缓蚀剂浓度的影响最小。在整个退膜过程中,膜层退除量与退膜时间并不呈线性关系。退膜开始阶段及完成阶段,膜层退除量大,退膜速率高；退膜中期,膜层退除量与退膜时间基本呈线性关系,且退膜速率小于初始退膜速率。 XRD分析显示,退膜后的镁合金表面无残余腐蚀产物。二次微弧氧化膜层的SEM图像显示,微孔结构致密,分布均匀,与一次微弧氧化的膜层无明显差别。结论镁合金微弧氧化膜层退除液的最佳配方为：硝酸90 mL/L,柠檬酸8 g/L,氟化钾35 g/L,十二烷基苯磺酸钠5 g/L,缓蚀剂6.5 g/L。该退膜液退膜效果良好,对镁合金基体损伤小,退膜速率快,成本低廉,可用于不合格镁合金零部件微弧氧化膜层的多次退除返修。

Objective To propose a stripping process of the magnesium alloy micro-arc oxidation coating, so as to improve the reutilization of the magnesium alloy. Methods The chemical solutions which contained nitrate acid, potassium fluoride, citric acid, SDBS and corrosion inhibitor was used to strip of the coating, and the orthogonal experiment was designed to optimize the formula-tion of the coating stripping solution, using the stripping rate and surface roughness and the judgment criteria. The role of each component in the coating stripping solution was analyzed. The relationship between the weight loss and time during the stripping process, and the relationship of coating thickness with corrosion rate and roughness were discussed. The optimized coating stripping solution was then used to strip the magnesium alloy micro-arc oxidation coating, and the macro- and microstructure of the surface was observed. Results The extreme difference of the chemical reagents on the stripping rate and surface roughness of the magnesi-um alloy substrate after stripping was in the order of Rnitrate acid>RKF>Rcitric acid>RSDBS>Rcor osion inhibitor , indicating that the concentration of nitrate acid had the biggest effect on the stripping rate and surface roughness, followed by the concentration of potassium fluo-ride, and the concentrations of citric acid, SDBS and corrosion inhibitor had the least effect. During the whole process, the weight loss and the time did not have a linear relationship. The weight loss and the stripping rate were high in the beginning and at the end of the process, while in the middle of the process the weight loss and the time had a linear relationship, with a stripping rate lower the initial stripping rate. There were no corrosion products on the surface of the magnesium alloy according to the XRD pattern. As shown by SEM, the pores in the layer after the second micro-arc oxidation treatment on magnesium alloy were compact and uni-form, which had no obvious difference with the coating after the first treatment. Conclusion The best composition of the stripping so-lution for of the magnesium alloy micro-arc oxidation coating was nitric acid 90 mL/L, citric acid 8 g/L, potassium fluoride 35 g/L, dodecyl benzene sulfonic acid sodium 5 g/L, and corrosion inhibitor 6. 5 g/L. This solution led to good stripping of the magnesium al-loy arc oxidation coating, causing little damage to the magnesium alloy substrate, and with high stripping rate and low cost. It can therefore be use to repeatedly strip and repair the unqualified magnesium alloy parts covered with the micro-arc oxide coating.