鳞片石墨对镁合金表面聚苯胺环氧涂层防护性能的影响

Effect of Flake Graphite on Protection Performance of Epoxy Coating Containing Polyaniline on the Magnesium Alloy Surface

目的针对聚苯胺环氧涂层物理屏蔽性能欠佳的问题,通过引入具有片层结构的鳞片石墨,从而进一步提高涂层对镁合金的腐蚀防护性能。方法利用化学氧化聚合法在鳞片石墨表面合成聚苯胺,通过X射线衍射仪、扫描电子显微镜、傅里叶变换红外光谱仪,对所得到的聚苯胺/鳞片石墨复合粉末进行表征。将合成的复合粉末均匀分散于环氧树脂中后,在AZ91D镁合金表面制备涂层,通过电化学阻抗测试对涂层在3.5%氯化钠溶液中的腐蚀防护性能进行研究。结果聚苯胺可以在鳞片石墨的表面聚合,鳞片石墨的加入使聚苯胺环氧涂层的附着力略有降低,涂层硬度、柔韧性及耐冲击性能没有明显改变,但鳞片石墨的加入明显提高了聚苯胺环氧涂层的阻抗值。在浸泡前1488 h,苯胺与鳞片石墨的质量比为1∶1时,涂层的阻抗值为1.3×10^(8)Ω·cm^(2),防护性能最好。但随着浸泡时间的延长,苯胺与鳞片石墨的质量比为4∶1时,涂层的阻抗值逐渐高于其他涂层,当浸泡4008 h后,其阻抗值为1.6×10^(8)Ω·cm^(2),仍具有较优异的防护性能。结论环氧涂层中添加聚苯胺/鳞片石墨复合粉末后,通过鳞片石墨前期的屏蔽与聚苯胺长期缓蚀的协同作用达到了对镁合金较好的防护效果,而涂层的这一防护效果和苯胺与鳞片石墨比例有关。

Targeting at the poor physical shielding performance of the epoxy coating containing polyaniline,this paper aims to further improve the corrosion protection performance of epoxy coating containing polyaniline(PANI)on magnesium alloys by adding the flake graphite with lamellar structure into the coating.Firstly,PANI was synthesized on the surface of flake graphite via chemical oxidation polymerization.The synthetic PANI/flake graphite composite powder was characterized by X-ray diffractometer,scanning electron microscope and Fourier transform infrared spectrometer.Then different coatings were prepared on the surface of AZ91D magnesium alloy after the composite powder was dispersed evenly in epoxy resin.At last,the corrosion performances of different coatings in 3.5wt%sodium chloride solution was studied by electrochemical impedance test.The results indicate that PANI can be polymerized successfully on the surface of flake graphite,the adhesion of the epoxy coating containing polyaniline was slightly reduced with the addition of flake graphite,and there is no apparent effect on the hardness,flexibility and impact resistance of the coating,but the addition of flake graphite significantly increased the impedance value of the epoxy coating containing polyaniline.When the ratio of aniline to flake graphite was 1∶1,the impedance value of coating was 1.3×10^(8)Ω·cm^(2) after being soaked in the solution for 1488 hours,and the coating had an excellent protection performance.However,with the extension of the soaking time,the impedance value of the coating was gradually higher than that of the other coatings when the ratio of aniline to flake graphite was 4∶1.After being soaked for 4008 hours,its impedance value was 1.6×10^(8)Ω·cm^(2),and the coating still had a good protection performance.Therefore,it can be concluded that,after the addition of PANI/flake graphite composite powder in the epoxy coating,a better protection effect on magnesium alloy is achieved through the mechanism of the synergy between shield effect of flake graphite in the early stage and the long-term corrosion inhibition effect of PANI,and that the protection effect of this coating is related to the ratio of polyaniline to flake graphite.