AZ91镁合金表面MgFe_2O_4薄膜的溶胶-凝胶法制备及其耐蚀性能

MgFe2O4耐酸耐碱,但目前还未见将其制成镁合金防腐蚀涂层的报道。采用溶胶-凝胶法在AZ91镁合金表面制备了MgFe2O4薄膜,利用正交试验研究了镀膜层数、溶胶中Mg2+与Fe3+的摩尔比、烧结温度、烧结时间对AZ91镁合金膜试样自腐蚀电流密度的影响,得出最优方案,并研究了优化条件制备的膜试样的组织结构及耐蚀性。结果表明:各因素对AZ91镁合金膜试样自腐蚀电流密度的影响程度由大到小依次是镀膜层数、烧结温度、nMg2+/nFe3+、烧结时间;最优条件是镀膜1层,nMg2+/nFe3+=0.35,烧结温度400℃,烧结时间5 h;与AZ91镁合金基体相比,优化条件制备的MgFe2O4薄膜的自腐蚀电流密度降低了1个数量级,自腐蚀电位正移了690 mV,耐腐蚀性能得到很大提高。

Preparation of MgFe2O4 Film on AZ91 Magnesium Alloy via Sol-Gel Route and Evaluation of Its Corrosion Resistance

MgFe2O4 films were prepared on the surface of AZ91 magnesium alloy by sol-gel method. The effects of the layer number of sol-gel coating, molar ratio of Mg2+/Fe3+ in the sol, sintering temperature and sintering time on the corrosion current density of the coated Mg alloy specimens were investigated by orthogonal test. The optimal condition for preparing MgFe2O4 films was established, and the microstructure and corrosion resistance of the sol-gel film prepared under the optimal condition were analyzed. It was found that various factors, depending on their effect on the corrosion current density of the coated Mg alloy specimens, could be ranked as layer number of coating> sintering temperature > molar ratio of Mg2+/Fe3+ in the sol > sintering time. The optimal film-formation condition was determined as layer number of 1, molar ratio of 0.35, sintering temperature of 400 ℃ and sintering time of 5 h. As compared with the Mg alloy substrate, as-prepared MgFe2O4 film obtained under the optimal condition possessed much better corrosion resistance, showing corrosion current density lower than that of the substrate by one order of magnitude and corrosion potential positively shifted by 690 mV.