【作者】 刘昕；

【导师】 朱雪梅；

【作者基本信息】 大连交通大学 ， 材料学， 2006， 硕士

【摘要】 以单宁酸溶液处理Fe30Mn2.7Si恒弹性合金，在其表面形成兰色化学转化膜，并采用溶胶-凝胶镀膜法在Fe30Mn2.7Si合金单宁酸化学转化膜表面提拉TiO₂溶胶-凝胶，经400℃保温30min烧结，获得均匀、致密的单宁酸／TiO₂复合膜。采用X-射线衍射（XRD）、傅立叶红外光谱（FTIR）、扫描电镜（SEM）、能谱（EDS）、电化学阳极极化及电化学阻抗谱等技术研究单宁酸化学转化膜和单宁酸／TiO₂复合膜的表面形貌、结构、成分与电化学腐蚀性能及机理。研究结果表明，单宁酸化学转化膜是由有一定孔隙的非晶态合金单宁酸膜层构成，两层单宁酸／TiO₂复合膜均匀、致密、无明显的孔隙，其膜厚约8μm。 阳极极化测量结果表明，单宁酸／TiO₂复合膜在1mol l^-1 Na₂SO₄溶液中产生自钝化，而单宁酸化学转化膜和原始试样都处于活化溶解状态，两层TiO₂复合膜与单宁酸化学转化膜的自腐蚀电位E_corr分别比Fe30Mn2.7Si合金提高325mV和63mV，自腐蚀电流密度I_corr均降低一个数量级；单宁酸／TiO₂复合膜在1％NaOH溶液中形成的钝化膜由Fe₂O₃、SiO₂与TiO₂复合组成，其稳定性、致密性和均匀性提高，两层TiO₂复合膜与单宁酸化学转化膜的自腐蚀电位E_corr分别比原始试样提高535mV和61mV，两层TiO₂复合膜的致钝电流密度I_c和维钝电流密度I_p比单宁酸化学转化膜降低一个数量级，比Fe30Mn2.7Si合金下降两个多数量级；TiO₂复合膜在3.5％NaCl溶液中呈现自钝化和点蚀击穿过程，两层TiO₂复合膜的点蚀击穿电位E_b为1050mV，远高于1Cr18Ni9Ti不锈钢，但是单宁酸化学转化膜与原始试样一样，处于活化溶解状态。电化学阻抗谱提示，两层TiO₂复合膜的电极反应主要由扩散过程控制，而单宁酸化学转化膜和Fe30Mn2.7Si合金的电极反应主要由电荷传递步骤控制。 单宁酸／TiO₂复合膜阻滞氧气和其他离子在溶液与合金表面之间的迁移和扩散，这种阻碍作用超过单一单宁酸转化膜的阻挡作用。因而单宁酸／TiO₂复合膜更强烈抑制腐蚀电极反应，更有效地降低金属的腐蚀速率，更进一步提高合金的耐蚀性能。更多还原

【Abstract】 A blue chemical conversion film was obtained on Fe30Mn2.7Si alloy by treating the alloy with tannic acid solution, then, tannic/TiO₂ composite film treated at 400 ℃ for 30 minutes was composited on the surface of tannic chemical conversion film prepared on Fe30Mn2.7Si alloy substrate by sol-gel method and the dip-coating process. Surface morphology, structure and compositions, and electrochemical corrosion resistance of tannic chemical conversion film and Tannic/TiO₂ composite film formed on the Fe30Mn2.7Si alloy have been studied by X- ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy, energy diffraction spectroscopy, anodic polarization and electrochemical impedance spectroscopy. The results show that the tannic chemical conversion film is probably constituted of amorphous and pored alloying tannate chelate, and the surface of two-layer T1O2 composite film is homogeneous and compact, and has no visible pore, and the thickness of this film is about 8 μm.In 1 mol l^-1 Na₂SO₄ solution, tannic/TiO₂ composite film can be passivated, but tannic chemical conversion film and Fe30Mn2.7Si alloy are active, and the corrosion potential E_corr of two-layer TiO₂ composite film increases more 325 mV than that of Fe30Mn2.7Si alloy, more 63 mV than that of tannic chemical conversion film, while the corrosion current density I_corr decreases by one order of mangnitude both.The passive film of tannic/TiO₂ composite film is composed of a mixture of Fe₂O₃, SiO₂ and TiO₂ in 1% NaOH solution, which improves the stability, uniformity and compactness of tannic/TiO₂ composite film. The corrosion potential E_corr of two-layer TiO₂ composite film increases more 535 mV than one of Fe30Mn2.7Si alloy, more 61 mV than one of tannic chemical conversion film. The critical passivation current density I_c and passive current density I_p decrease by one order of mangnitude than that of chemical conversion fllm.and two orders of mangnitude than that of Fe30Mn2.7Si alloy. The pitting corrosion potential E_b of two-layer TiO₂ composite film is 1050 mV in 3.5% NaCl solution. It is by far higher than 1Cr18Ni9Ti stainless steel. But tannic chemical conversion film is active, as the same of Fe30Mn2.7Si alloy. The electrochemical impedance spectroscopy更多还原