镁合金表面硅烷化及阴极电泳涂层的研究

Research on Silane and Cathodic Electrophoretic Coatings on Magnesium Alloys

硅烷和磷化预处理后采用阴极电泳技术在AZ31B镁合金表面制备有机涂层,并与传统喷漆涂层性能进行对比。测试了涂层的硬度,结合力及耐冲击性能。采用盐水浸泡、盐雾试验及阻抗谱测试(EIS)研究了涂层的耐腐蚀性能。利用扫描电镜分析了涂层的表面形貌。结果表明,硅烷和磷化处理均有助于提高电泳涂层与基体的结合力,阴极电泳涂层的综合机械性能要优于喷漆涂层。硅烷处理后电泳试样盐水浸泡24 h后,低频阻抗值达到109Ω,远远高于磷化处理后电泳及传统喷漆试样,其耐腐蚀性能更好。盐雾试验结果表明,硅烷处理后电泳试样1 000 h表面无变化,其耐腐蚀性能最佳。

Organic coatings were deposited using cathodic eleetrodeposition （E-coat） on AZ31B magnesium alloys pretreated by sialne and phosphate. The performance of organic coatings was compared with that got by traditional paint technology. Surface morphology of the coatings was obtained by scanning electron microscope （SEM）. Hardness, adhesion and impact resistance of the coatings were tested. Besides, corrosion resistance of the coatings was evaluated by salt solution immersion, salt spray test and electrochemical impedance spectroscopy （EIS）. The results showed that the adhesion of the E-coat on AZ31B magnesium alloys could be improved by silane and phosphate pretreatments. The mechanical properties of E-coat, Compared with painting, revealed much better. The impedance value of the coating pretreated by silane was 10^9 Ω at low frequency after 24 hours immersion in 3.5 % NaCl solution, which was higher than those of painting and coating pretreated by phosphate. Therefore, the coating pretreated by silane on AZ31B magnesium alloys had the best corrosion resistance among three coatings. Furthermore, this result was also proved by 1000 h slat spray test.