摘要
Sol-gel coatings containing various amounts of hydroxylated nanodiamond(HND)particles were applied on the magnesium alloy for corrosion protection.The micrometric defects in the sol-gel coating completely disappeared after adding 0.01,0.02 and 0.05 wt.%of the HND nanoparticles.The AFM analyses showed that average roughness of the sol-gel film is about 6.7 nm which increases to 16.1 and 20.2 nm after incorporating 0.005 and 0.02 wt.%of the HNDs,respectively.The corrosion resistance of the coatings was tested in Harrison’s solution by means of EIS technique after 15,30,60 and 120 min immersion.The corrosion resistance of the sol-gel coating was remarkably enhanced by incorporating different contents of the HNDs and the best result was obtained for 0.01 wt.%.The results of the EIS experiments were confirmed by the potentiodynamic polarization tests.The corrosion resistance enhancement was attributed to the film compactness(due to the chemical interaction with the HNDs),formation of tortuous pathways for diffusion of the corrosive solution,and filling of the defects by the nanoparticles.However,the beneficial effect of the HNDs on the corrosion resistance gradually diminished as the content of nanoparticle was increased.Finally,the micromorphology of the sol-gel nanocomposites was studied after the corrosion tests.
在镁合金表面涂覆含不同比例羟基化纳米金刚石(HND)颗粒的溶胶凝胶防腐蚀涂层。加入0.01%、0.02%和0.05%(质量分数)HND颗粒后溶胶凝胶涂层中的微缺陷完全消失。AFM分析表明,加入0.005%和0.02%的HND颗粒后,溶胶凝胶层的平均粗糙度从约6.7 nm分别增加到16.1 nm和20.2 nm。在Harrison溶液中分别浸泡15、30、60和120 min后,用电化学阻抗谱(EIS)技术测试涂层的耐蚀性。加入不同浓度的HND颗粒可显著提高溶胶凝胶涂层的耐蚀性,并在0.01%时获得最佳结果。通过动电位极化试验验证电化学阻抗谱实验的结果。耐腐蚀性的增强是由于涂层的致密性(由于基体与HND颗粒产生化学作用)、腐蚀溶液曲折扩散路径的形成以及纳米颗粒对缺陷的填充。然而,随着纳米颗粒含量的增加,HND对耐腐蚀性的有利影响逐渐减弱。最后,对腐蚀实验后的溶胶凝胶纳米复合涂层的显微形貌进行研究。
