添加剂对镁合金表面Ce-Mn转化膜组织和耐蚀性能的影响

Effect of additives on the microstructure and corrosion resistance of Ce-Mn chemical conversion coating on magnesium alloy

以Ce(NO3)3-KMn O4为主要成膜剂,向体系中分别加入NH4HF2、Na F、Sr Cl2、Na BF4、十二烷基苯磺酸钠(C18H29-Na O3S)、Na B4O7添加剂,室温下在镁合金表面制备了Ce-Mn转化膜。用扫描电镜(SEM)及能谱仪(EDS)对转化膜的微观形貌和成分进行分析,并用极化曲线研究转化膜的耐腐蚀性能。结果表明,添加剂不改变膜层成分,但对膜层组织结构及耐腐蚀性能有较大影响,较佳的添加剂为十二烷基苯磺酸钠,添加十二烷基苯磺酸钠生成的转化膜,膜层裂纹细小,耐蚀性更好。

With Ce（ NO3）3-KMn O4 as the main film former,Ce-Mn-based chemical conversion coating was prepared on the surface of magnesium alloy by adding the additives of NH4HF2,Na F,Sr Cl2,Na BF4,,C18H29 Na O3S,Na B4O7 correspondingly into the system at room temperature. The surface morphology and the composition of the conversion coating were analysed by SEM and EDS,respectively. The corrosion resistance of the specimens was investigated by potentiodynamic polarization curves. The results show that the additives have great impacts on the microstructure and corrosion resistance of the coating without changing its compositions. The optimal additive for Ce-Mn chemical conversion coating is C18H29 Na O3S. Homogeneous Ce-Mn chemical conversion coating can be formed on the surface of magnesium alloy in the solution with the additive of C18H29 Na O3S. The Ce-Mn conversion coating can increase the corrosion resistance with tiny cracks in the coating.