AZ31B镁合金表面锑酸盐转化涂层的制备、耐腐蚀性及其改进研究

Preparation,corrosion resistance,and its improvement of antimonate conversion coating on AZ31B magnesium alloy

采用化学转化法,在KSb(OH)6和H_(2)O_(2)存在下,在AZ31B合金表面成功制备了同时含有Sb(V)和Sb(Ⅲ)的涂层。研究了锑酸盐转化涂层经添加C6H11O7K和后处理后涂层表面形貌变化及其对腐蚀性能的影响。分别用扫描电子显微镜(scanning electron microscope,SEM)、Raman光谱和光电子能谱仪(X-ray photoelectron spectroscopy,XPS)对涂层的成分、表面形貌和晶体结构进行了表征,采用动电位极化曲线测试,以及中性盐雾试验评估了涂层的抗腐蚀性能。结果表明:涂层主要成分含有Mg^(2+)、Al^(3+)、K^(+)、[Sb(OH)_(6)]^(-)和Sb(Ⅲ)。当KSb(OH)_(6)与C6H11O7K的浓度比为2:1时,有助于涂层的生长;随着KSb(OH)_(6)溶液浓度的增大,涂层的Sb含量增大,生长速度加快;涂层的最低腐蚀电流密度为1.50×10^(-6)A/cm^(2);经过8-羟基喹啉和硅酸钠混合溶液的后处理,腐蚀电流密度进一步下降到6.00×10^(-7)A/cm^(2),中性盐雾试验由24 h提高到120 h以上,明显地改善了镁合金的耐腐蚀性能。

Coatings containing both Sb(V)and Sb(III)were successfully prepared on the surface of AZ31B alloy by chemical conversion method in the presence of KSb(OH)6 and H_(2)O_(2).The changes of the surface morphology of the antimonate transformed coatings after the addition of C6H11O7K and post-treatment and their effects on the corrosion properties were investigated.The composition,surface morphology and crystal structure of the coatings were characterized by scanning electron microscope(SEM),Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS),respectively,and the corrosion resistance of the coatings was evaluated using dynamic potential polarization curve tests,as well as neutral salt spray tests.The results showed that the main components of the coating include Mg^(2+),Al^(3+),K^(+),[Sb(OH)_(6)]^(-),and Sb(III).When the concentration ratio of KSb(OH)_(6)to C6H11O7K was 2:1,it is beneficial for the growth of the coating.As the concentration of KSb(OH)_(6)solution increases,the Sb content of the coating increases and the growth rate is accelerated.The lowest corrosion current density of the coating was 1.50×10^(-6)A/cm^(2).After post-treatment with a mixed solution of 8-hydroxyquinoline and sodium silicate,the corrosion current density further decreased to 6.00×10^(-7)A/cm^(2),the neutral salt spray test indicated that the anti-corrosion times increased from 24 h to 120 h,the corrosion resistance of magnesium alloys could be significantly improved.