镁合金表面制备耐久性超疏水复合膜及其性能

Preparation of durable superhydrophobic composite film on magnesium alloy and its performance

用磷化工艺在AZ31B镁合金表面制备锌系磷化膜,后均匀涂覆改性硅溶胶,固化后成与磷化膜结合形成复合膜。研究复合膜的微观形貌、成分、静态接触角、耐久性及耐蚀性,与镁合金比较。结果表明:复合膜具有纳米级和微米级凸起或孔隙交错分布的微/纳米分级结构,主要含有Zn、P、O、C和Si,与镁合金基体紧密结合能稳定保持超疏水性,纯水和水性介质在复合膜表面的静态接触角都大于150°。在质量分数为3.5%的氯化钠溶液中浸泡24 h后,复合膜的腐蚀电流密度较镁合金基体降低了近两个数量级,仅为6.79×10^(-7)A/cm^(2),极化电阻约为镁合金的3.3倍,耐久性和耐蚀性良好。由于复合膜具有微/纳米分级结构且表面能低,对纯水和水性介质都表现出强疏水作用,能有效阻隔腐蚀介质,增大腐蚀阻力,为AZ31B镁合金提供理想的腐蚀防护。

A zinc phosphating film was prepared on the surface of AZ31B magnesium alloy by phosphating process as the bottom layer,and then the modified silica sol was uniformly coated and solidified to form a film that was closely combined with the phosphating film to form a composite film.The microstructure,composition,static contact angle,durability and corrosion resistance of the composite films were studied and compared with those of magnesium alloy.The results show that the composite film mainly composed of Zn,P,O,C and Si elements,and has a micro/nano hierarchical structure composed of nano-scale and micro-scale protrusions or staggered pores.The composite film closely combined with the magnesium alloy matrix,which can stably maintain superhydrophobicity,and the static contact angle of pure water as well as water-borne media on the composite film surface are greater than 150°.After immersion in 3.5%sodium chloride solution for 24 h,the corrosion current density of composite film is nearly two orders of magnitude lower than that of magnesium alloy matrix,only 6.79×10^(-7)A/cm^(2),and the polarization resistance is about 3.3 times higher than that of magnesium alloy matrix,showing good durability and corrosion resistance.Since the composite film has a micro/nano hierarchical structure and low surface energy,it exhibits strong hydrophobic effect on both pure water and aqueous media,effectively blocking corrosion media and increasing inhibition of corrosion.The composite film can provide ideal corrosion protection for AZ31B magnesium alloy.