不同链长的烷基硫醇自组装膜在不同腐蚀介质中的抗腐蚀性阻抗研究

文章通过在铜表面上制备高质量的不同链长的烷基硫醇自组装膜并研究烷基硫醇自组装膜在不同腐蚀介质NaCl、HCl、H2SO4中的抗腐蚀能力,从而对其抗腐蚀性能进行比较研究。结果表明:铜电极上组装的C18SH、C12SH、C6SHSAMs在不同的腐蚀介质中对基底均有相当好的腐蚀保护作用;在其它条件相同的情况下,烷基硫醇的碳链越长,自组装膜对铜基底的腐蚀保护能力越强。     

添加剂对镀锌层钝化膜耐蚀性的影响

利用极化曲线和交流阻抗谱,研究了不同添加剂对镀锌层烷氧基硅烷钝化膜腐蚀性能的影响,并与加速腐蚀试验结果进行了对比.实验结果表明:添加剂的加入明显改变了钝化膜层的腐蚀电位,提高钝化膜在低频区的交流阻抗值,烷氧基硅烷钝化膜的耐蚀性明显提高.     

锰酸锂的SEI膜研究

通过循环伏安(CV)、电化学交流阻抗谱(EIS)及恒流充放电研究锰酸锂表面的成膜性能及电化学性能。结果表明,锰酸锂表面的SEI膜在电池首次充电过程中就开始形成,充放电循环至3周时,SEI膜得到较大程度的修补和完善。但循环到一定次数后,SEI膜会逐渐变厚,直接影响电池的电化学性能。     

镀锌钝化膜耐蚀性能的研究

简单介绍了新开发的ＣＨ钝化工艺及其特点,用恒电量技术对比测试了ＣＨ钝化工艺形成的经膜和常规钝和化膜,ＣＨ钝化膜的Ｒｐ、Ｒｆ值大,Ｃｄ、Ｃｆ值小;再应用循环伏安法在－１．０２－－１．６８Ｖ范围进行测试,发现ＣＨ钝化膜的循环伏安图经１０次循环后仍与第一次的一样。两种测试说明了ＣＨ钝化膜常规钝化的耐蚀性高。两种电化学测试的结果与其它方法的结果的一致。     

镀锌钢板墨绿色钝化膜的腐蚀行为

采用极化曲线、电化学阻抗谱和中性盐雾试验,研究了镀锌钢板墨绿色钝化膜的耐蚀性.在质量分数为5%的NaCl溶液中,钝化试样的腐蚀电位较未钝化试样明显正移,腐蚀电流密度大幅降低.镀锌未钝化及钝化试样的Nyquist谱图呈现2个较为完整的容抗弧,说明腐蚀体系受电化学控制.墨绿色钝化试样的容抗弧半径较未钝化试样大,因为钝化膜的形成增大了腐蚀过程的反应电阻,从而提高了试样的耐腐蚀性能.在中性盐雾试验中,镀锌墨绿色钝化试样的耐白锈时间达到400 h.     

聚苯胺纳米纤维的合成及其在环氧树脂中对Q235钢的防腐蚀性能

分别采用直接混合氧化法和界面聚合法在四种不同的无机酸体系中制备了聚苯胺纳米纤维。扫描电镜表征发现采用直接混合氧化法可以得到高品质的聚苯胺纳米纤维,且在硫酸体系中可以得到直径均匀,长度达几个微米的优异的纤维形貌;通过红外光谱和紫外光谱对聚苯胺产物进行结构表征显示所得产物为掺杂态聚苯胺。进一步,选择硫酸掺杂的聚苯胺与环氧树脂共混制备了复合涂层,电化学阻抗谱研究发现,聚苯胺的加入提高了环氧涂层对Q235钢的初始屏蔽保护效果,但浸泡后,保护效果迅速下降。     

超声波清洗对镀锡钝化膜耐蚀性能的影响

钢板经镀锡、软熔及重铬酸盐电解钝化后,在其表面残留的六价铬和黑灰严重影响锡层的耐腐蚀性能。利用超声波清洗钝化后的镀锡板,达到去除镀锡板缺陷处的六价铬和黑灰而不影响镀锡板表面性能的目的。研究了超声波频率、清洗时间和温度对镀锡板耐腐蚀性能的影响。结果表明:超声波清洗能够提高镀锡层的耐蚀性。     

硝酸镧对锌铝镁合金表面钝化膜耐蚀性的影响

为解决锌铝镁钢板的耐蚀性问题，以硝酸镧作为稀土添加剂在其表面制备丙烯酸树脂-硅烷-稀土钝化膜层。采用扫描电子显微镜、X射线衍射光谱分析、电化学工作站、中性盐雾试验等方法，研究了不同硝酸镧添加量对钝化膜结构及耐蚀性的影响。结果表明，钝化膜以堆积方式沉积到基材表面，硝酸镧添加量为0.5%时，耐盐雾试验时间可达到72 h，腐蚀电流密度降低至1.11×10^-6A·cm^-2，相较于基体降低了两个数量级，耐黑变性良好。     

LY12铝合金表面硅烷杂化膜的电化学性能研究

以γ-缩水甘油醚基丙基三甲氧基硅烷(GPTMS)和甲基三乙氧基硅烷(MTES)为前驱体,制备了正硅酸乙酯(TEOS)改性溶胶,并在LY12铝合金表面制得了2种有机硅烷杂化薄膜.对裸铝合金、钝化膜和硅烷杂化膜合金电极进行了动电位极化曲线和电化学阻抗谱(EIS)测试,评价了各化学转化膜的防腐蚀性能.结果表明:有机硅烷杂化膜可有效提高铝合金的耐蚀性,其耐蚀效果与传统铝合金表面钝化膜相当,其中GPTMS/TEOS膜的性能更优于钝化膜.     

Electronic band structure of passive film on X70 pipeline steel

Mott-Schottky analyses and photoelectrochemical measurements were used to explore the effects of film formation potentials, time, and chloride ions on the electronic properties of the passive film on X70 pipeline steel in 0.5 M NaHCO₃. Mott-Schottky analyses showed that with increasing film formation potentials, the capacitance and donor density of the passive film decrease, and the flat band potential and thickness of the space charge layer increases. The addition of chloride ions increases the capacitance and donor density of the film and results in a more negative flat band potential and a thinner space charge layer. Photoelectrochemical measurements imply that photo-generated carriers with a low mobility exist in the passive film and the photocurrents of the film increase when the film formation potential becomes more positive. The bandgap energy, E_g, of the passive film decreases with increasing film formation potentials. The extension of film formation time increases the photocurrents and leads to a decrease in the bandgap energy of the passive film. The effect of film formation time on the photocurrents of the film formed at 0.6 V_SCE was less remarkable than that formed at 0.2 V_SCE. The existence of chloride ions in 0.5 M NaHCO₃ decreases the photocurrents and increases the bandgap energy of the passive film.     

EIS investigation of passive film formation on mild steel in oxalic acid solution

The properties of oxide films on mild steel formed anodically in aqueous solution containing oxalic acid were investigated by means of electrochemical impedance spectroscopy (EIS). The morphology of the passive layers at different stages of film formation was investigated using scanning electron microscopy (SEM). Passivation of mild steel in oxalic acid solution is a multi-stage process that occurs before passive layer breakdown. The influence of potential on the electrochemical behavior of the passive layer was also investigated. Depending on the passive layer potential, the EIS spectra obtained exhibited a one- or two-time constant system. This suggests the formation of either a one layer or two layer oxide film on the mild steel surface, depending on the passivation potential.     

Influence of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in bicarbonate/carbonate buffer solution

The influences of temperature, chloride ions and chromium element on the electronic property of passive film formed on carbon steel in NaHCO₃/Na₂CO₃ buffer solution are investigated by capacitance measurement and electrochemical impedance spectroscopy (EIS). The results show that the passive film appears n-type semiconductive character; with increasing the solution temperature, the addition of chromium into carbon steel and increasing the concentration of chloride ions, the slopes of Mott–Schottky plots decrease, which indicates the increment of the defect density in the passive film. EIS results show that the transfer impedance R₁ and the diffusion impedance W decrease with increasing the solution temperature, with the addition of chromium into carbon steel and with increasing the chloride ions concentration. It can be concluded that the corrosion protection effect of passive film on the substrate decreases with increasing the solution temperature, adding chromium into carbon steel and increasing chloride ions concentration.     

EIS study of potentiostatically formed passive film on 304 stainless steel

Passive film was potentiostatically grown on Type 304 stainless steel at potentials between −0.4 and 0.3 V vs. Hg/HgSO₄ in 50 mV intervals. Electrochemical impedance spectroscopy was used to study properties of the grown passive films. Relevant circuit analogs were selected to fit the electrochemical impedance data obtained at each potential. The resultant parameters were used to calculate film thickness through both film capacitance and resistance. The calculated thicknesses were compared with ellipsometry thickness measurement results. An overestimation occurred when the film resistance was used to calculate the film thickness. On the other hand, when the CPE parameter Q was used, the film thickness was underestimated. Available approaches were employed to calculate the effective capacitance of the film. A comparison between the film thickness calculated from the effective capacitance and ellipsometry measurements suggested a surface distribution of time constants on the surface.     

Effects of solution temperature on electronic properties of passive film formed on Fe in pH 8.5 borate buffer solution

Effects of solution temperature on the electronic properties of passive film formed on Fe in pH 8.5 borate buffer solution were investigated to clarify why the passive current density of Fe increases with solution temperature. The Mott-Schottky analysis and photocurrent measurement were employed to determine the electronic properties of the film. The Mott-Schottky analysis and photocurrent measurement revealed that as solution temperature increased, the concentration of oxygen vacancy in the passive film increased accompanying with an increase in the concentration of Fe²⁺ ion in the γ-Fe₂O₃ passive film due to a charge neutrality reaction in the film. Further, the increase in passive current density of Fe with solution temperature was found due primarily to the increase in the concentration of oxygen vacancy in the passive film, which is well explained by the point defect model (PDM).     

正极材料钴酸锂表面固体电解质相界面膜的研究

通过循环伏安和交流阻抗（EIS）分析,对锂离子电池正极材料钴酸锂（LiCoO₂）表面的固体电解质相界面膜（SEI膜）的形成进行了研究。循环伏安测试结果表明,钴酸锂表面的SEI膜主要是在第1次循环过程中形成。EIS测试结果表明,在低倍率条件下和常温条件下充放电循环形成的SEI膜更加致密,阻抗值更小;储存时间的长短对电池的阻抗也有影响,储存7 d的阻抗值要小于储存1 d的阻抗值。     

Electrochemical investigation of the effects of hydrogen on the stability of the passive film on iron

The effects of hydrogen on the stability of passive films on iron were investigated by electrochemical methods: open circuit potential decay, cathodic galvanostatic reduction, electrochemical impedance spectroscopy, and breakdown potential measurements. The results show that hydrogen decreases the final static open circuit potential, the cathodic charge for reduction and the charge transfer resistance of the passive film, indicating that hydrogen decreases the stability of the passive film. The charge transfer resistance of the passive film formed on the charged specimen does not change with increasing the film formation potentials, suggesting that increasing film formation potentials under hydrogen charging conditions cannot improve the stability of the passive film. Hydrogen decreases the breakdown potential of the passive film, especially at lower chloride ion concentrations, confirming that hydrogen promotes the susceptibility of the passive film on iron to pitting corrosion. The reasons why hydrogen decreases the stability of the passive film were discussed.     

Photoelectrochemical analysis on the passive film formed on Fe-20Cr in pH 8.5 buffer solution

The electronic properties of passive film formed on Fe-20Cr stainless steel in pH 8.5 buffer solution were examined by the photocurrent measurements of the film. The passive film on Fe-20Cr exhibited an n-type semiconductor, which was confirmed by anodic photocurrent. The photocurrent spectrum for the passive films formed on Fe-20Cr was almost same in shape to that for the passive film on Fe except for the large difference in photocurrent intensity, which demonstrated that the passive film on Fe-20Cr is composed of Cr-substituted γ-Fe₂O₃ involving the d-d and p-d electron transitions. However, the large difference in photocurrent intensity for passive film between Fe and Fe-20Cr was due presumably to the fact that Cr³⁺ ions in passive film act as effective recombination sites of electron-hole pairs. The abrupt increase in the photocurrent intensity for the passive film formed on Fe-20Cr at a transpassive potential is due presumably to the decrease in the recombination site resulting from the reduction of Cr³⁺ content accompanying the oxidation of Cr³⁺ to Cr⁶⁺ in transpassive region.     

The effect of thickness on the composition of passive films on a Ti-50Zr at% alloy

Anodic films were grown potentiodynamically in different electrolytes (pH = 1-14) on a Ti-50Zr at% cast alloy, obtained by fusion in a voltaic arc under argon atmosphere. The thickness of the films was varied by changing formation potential from the open circuit potential up to about 9 V; growth was followed by 30 min stabilization at the forming potential. Films having different thicknesses were characterized by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). Moreover, film composition was analyzed by X-ray photoelectron spectroscopy (XPS).Regardless of the anodizing conditions, passive films on the Ti-50Zr at% alloy consist of a single layer mixed oxide phase containing both TiO₂ and ZrO₂ groups. However, an enrichment of Ti within the passive film, increasing with the film thickness, is detected both by PCS and XPS. This leads to concentration profiles of Ti⁴⁺ and Zr⁴⁺ ions along the thickness, and to different electronic properties of very thin films (more insulating) with respect to thicker films (more semiconducting), as revealed by the photocurrent-potential curves.     

The influence of a mixed radiation environment on the properties of the passive film on tungsten

The properties of the passive film formed on the tungsten (W) in H₂SO₄ (pH 1.6) during proton irradiation (spallation) were characterized with electrochemical impedance spectroscopy (EIS), surface enhanced Raman spectroscopy (SERS), and the Mott-Schottky (MS) method. EIS data were associated with an adsorption pseudocapacitance. Observed changes in the adsorption pseudocapacitance were consistent with thinning of the outer layer of the passive film. SERS experiments found that the spallation environment had no affect on the molecular state of the oxide. Results from MS experiments found that the oxygen vacancy concentration in films formed during proton irradiation were lower than those films formed in the absence of irradiation. In accordance with the point defect model (PDM) for oxide films, a decrease in the oxygen vacancy concentration indicates proton irradiation alters the passive film by either decreasing the oxygen vacancy flux or increasing oxygen vacancy diffusion. Calculations using the LAHET and MCNP transport codes have demonstrated that spallation reactions are capable of generating numerous energetic particles such as, electrons, neutrons, protons, and photons. Each of these species is capable of generating a wide variety of defects in the oxide film altering its electronic and transport properties and, thus, explaining the observed electrochemical phenomena.