AZ31镁合金表面防腐涂层的制备及耐蚀性研究

【作者】 黄荣；

【导师】 陈明安；

【作者基本信息】 中南大学 ， 材料加工工程， 2011， 硕士

【摘要】 选择聚吡咯(PPy)作为涂层材料,在经硅烷预处理后的AZ31镁合金表面化学氧化合成PPy。运用傅立叶变换红外光谱(FTIR)研究了膜层结构,用扫描电镜(SEM)及能谱分析(EDS)研究了膜层表面形貌及成分分布特征,用电化学极化曲线、交流阻抗(EIS)测试和盐水浸泡实验评定了金属/膜层体系的耐蚀性能。研究了BTESPT和APS两种硅烷偶联剂对AZ31镁合金预处理后的耐蚀性能,硅烷在镁合金表面形成SiOSi网状薄膜结构,并通过SiOMg键与镁合金表面相连,由于硅烷的阻挡作用提高了镁合金的耐腐蚀性能。不同pH的3.5wt%NaCl溶液以碱性环境对金属/硅烷体系的腐蚀程度最轻,中性其次,酸性最严重。由于亲水的氨基基团,氨基硅烷对镁合金基体的保护性能比含硫硅烷略差。研究了预处理、氧化剂、反应温度和聚合时间等多种聚合参数对PPy形貌、耐蚀性的影响规律。PPy膜对镁合金腐蚀有一定的抑制作用,腐蚀电流密度降低了1个数量级；硅烷预处理提高Mg/PPy体系的耐蚀性能,使腐蚀电位正移了110mV,腐蚀电流密度减小了约2个数量级。其余聚合条件相同时,过硫酸铵((NH4)2S2O8)合成的PPy膜耐蚀性要比氯化铁(FeCl3)相对好。掺杂阴离子的存在对Mg/APS/PPy体系具有一定的缓蚀作用。以(NH4)2S2O8作氧化剂、十二烷基苯磺酸钠(SDBS)作掺杂剂时化学原位聚合的最佳时间是10min。5～10℃的聚合温度比室温好。探讨了PPy的成膜机理。PPy与基体之间是通过物理吸附连接,PPy的附着性和连续性较差,对镁合金的防护性能有限。经硅烷预处理后,硅烷膜一方面与金属基体通过SiOMg键结合,另一方面与PPy通过化学键连接,增强了PPy和镁基体的结合力,生成的薄膜附着力好,缺陷也相对较少,使Mg/silane/PPy的耐腐蚀性相应提高。更多还原

【Abstract】 Polypyrrole (PPy) was chemically synthesized on the surface of the silane pretreated AZ31 magnesium alloy. Fourier transform infrared spectroscopy (FTIR) was used for structural characterization of the formed silane and PPy films. Scanning electron microscope (SEM) and energy dispersive X-ray (EDS) analysis were used for observation of surface morphology and elements analysis of the films. The corrosion behavior of silane film and PPy film was studied in 3.5wt% NaCl solution using electrochemical polarization test, electrochemical impedance spectroscopy and immersion test at room temperature.The corrosion behavior of AZ31 Mg pretreated with BTESPT and APS silane respectively was studied. The silane moleculars were cross-linked through SiOSi, and the silane film was linked to the Mg alloy by SiOMg. Silane pretreatment can improve the corrosion protection performance of AZ31 Mg alloy and a lower corrosion rate correlated with higher pH. Mg/APS played worse anti-corrosion performance than Mg/BTESPT because of hydrophilic NH2 group.The anti-corrosion performances of PPy films through different polymerization processes were investigated, including pretreatment, oxidant, reaction temperature and time. The PPy film showed a certain corrosion inhibition on the AZ31 magnesium alloy, with a decrease in the corrosion current density by one order of magnitude. Silane pretreatment can improve the corrosion protection performance of the Mg/PPy system, causing a positive shift of the corrosion potential by 110 mV and a decrease in the corrosion current density by two orders of magnitude. PPy using (NH4)2S2O8 as an oxidant showed better protection performance than FeCl3. Doped anion played a certain corrosion inhibition in Mg/APS/PPy system.10min was the best polymerization time of PPy using sodium dodecyl benzene sulfonate (SDBS) as a doping agent and (NH4)2S2O8 as an oxidant. And polymerization at temperature of 5～10℃was better than at room temperature.The mechanism on formation of PPy film was discussed. PPy was connected to the Mg alloy by physical adsorption, which induced the poor adhesion and continuity of PPy film, decreased its corrosion protection performance. After silane pretreatmen, silane film was linked to the Mg alloy by SiOMg, while linked to PPy by chemical bond, which enhanced the adhesion between PPy and Mg matrix, made the arrangment uniform and reduced the defects of PPy film.更多还原