利用腐蚀失重和电化学测试方法，并结合SEM和TEM分析技术，研究增强相SiC颗粒的体积分数为2%，5%，10%和15%的SiCp/AZ91镁基复合材料 (MMCs)，在25 ℃条件下，含有饱和Mg(OH)2的3.5%NaCl溶液中的腐蚀行为。结果表明，SiCp/AZ91 MMCs的腐蚀速率明显大于AZ91镁合金，并且随SiC颗粒体积分数的增加而增大。SiC颗粒不与AZ91基体直接构成微电偶，但是SiC颗粒的加入改变了SiCp/AZ91 MMCs的显微结构从而提高了腐蚀速率。主要原因为随着SiC颗粒的加入β相晶粒细化，使β相与α相间的微电偶腐蚀电流密度增大；SiC颗粒的加入使大量的β相在SiC颗粒与AZ91基体界面处优先再结晶，致使该界面处β相与α相间的微电偶腐蚀加速，间接导致SiCp/AZ91 MMCs的腐蚀加速。
The corrosion behavior of the hot-extruded SiCp/AZ91 (MMCs), a magnesium alloy AZ91 based composite containing different amount SiC particles (i.e. 2%, 5%, 10% and 20% in volume fraction), was investigated in 3.5%NaCl solution saturated by Mg(OH)2 at 25 ℃ by means of mass loss method, electrochemical measurements, SEM and TEM observations and XRD. The results indicated that: The corrosion rate of the SiCp/AZ91 MMCs was much greater than that of AZ91 magnesium alloy, and which increased as the increasing volume fraction of micron-sized SiC. The strengthening SiC particles exhibited little tendency with the alloy matrix to form galvanic couple, thereby little tendency to induce galvanic corrosion in micro-scale. But the addition of SiC particles resulted in a highly change in microstructure of SiCp/AZ91 MMCs, as consequence, the corrosion resistance of the composite became significant inferior, in comparison with those of the AZ91 alloy. There were two main reasons responsible for the greater corrosion rate of SiCp/AZ91 MMCs. Firstly, SiC particles promoted grain refinement of β phase, which increased the micro-galvanic corrosion current density between β phase and α phase. Secondly, the addition of SiC particles promoted the dynamic recrystallization nucleation of β phase at the interface SiC particles/AZ91 matrix, which might be beneficial to the microgalvanic corrosion of the coupling of β phase and α phase there, therewith indirectly increased the corrosion rate of SiCp/AZ91 MMCs.
研究了镍基合金800H在550 ℃，25 MPa，600 ℃，25 MPa和650 ℃，25 MPa超临界水中的应力腐蚀开裂敏感性，及其在超临界650 ℃，25 MPa，次临界290 ℃，15.2 MPa水中的均匀腐蚀性能，同时研究了其在空气中不同温度条件下的机械强度。通过慢应变速率拉伸实验得到相应的应力-应变曲线。结果表明，随着温度的升高，800H的机械强度逐渐下降；SEM像表明800H在这3种工况下均具有应力腐蚀开裂的倾向。由其在空气中不同温度下的机械强度可知，其屈服强度和抗拉强度基本上随温度的升高而降低。800H在超临界水条件下的腐蚀实验表明，其腐蚀增重大致符合抛物线增长规律；而其在次临界条件下的腐蚀却呈现出减重的特征。
Susceptibility to stress corrosion cracking (SCC) of nickel based alloy 800H was studied in supercritical water at 550 ℃, 25 MPa, 600 ℃, 25 MPa and 650 ℃, 25 MPa respectively, and its general corrosion behavior in supercritical water at 650 ℃, 25 MPa and in subcritical water at 290 ℃, 15.2 MPa respectively as well. The mechanical properties of alloy 800H were also examined at different temperatures in air. The strain-stress curve of slow strain rate tensile (SSRT) tests shows that the strength of alloy 800H decreases as temperature increases. The ex situ scanning electron microscopy (SEM) observation shows that alloy 800H under the three conditions in supercritical water all exhibits susceptibility to SCC. The SSRT tests in air show that the yield strength and tensile strength of alloy 800H decrease as temperature rises. The results of general corrosion experiment in supercritical waters show that the weight gain of the alloy follows a parabolic law; however, in subcritical water the alloy exhibits mass loss.
The effect of preferred orientation on the corrosion behavior of hot-pressed and hot-deformed nanocrystalline NdFeB magnet was investigated by electrochemical measurements and materials analysis methods. The results indicated that the preferred orientation had little effect on the corrosion behavior of hot-pressed and hot-deformed nanocrystalline NdFeB magnet. Polarization and electrochemical impedance spectroscopy (EIS) measurements showed that the cross section vertical to the preferred orientation exhibited a higher dissolution rate and susceptibility to localized corrosion in 3.5%NaCl solution rather than that parallel to the preferred orientation. X-ray photoelectron spectroscopy (XPS) revealed that after immersion in 3.5% NaCl solution for 30 min, both of the surfaces of the two sections showed selective corrosion of Nd. The slight differences in the corrosion behavior of the two cross sections were probably ascribed to their differences in the Nd-rich phase proportions and the guantities of grain boundaries.
The crevice corrosion behavior of 5083 and 6061 aluminium alloys was investigated by electrochemical noise and in-situ measurement with microelectrode. The experimental results indicated that concerning the crevice corrosion process, 6061 alloy follows IR drop mechanism, while 5083 alloy follows critical solution composition theory. The corrosion of 5083 alloy was mainly uniform corrosion and transferred to severe localized corrosion with the increasing of crevice depth. But the 6061Alloy suffered from severe localized corrosion. The difference of corrosion behavior between 5083 and 6061 aluminium slloys might be attributed to the presence of different intermetallic phase for the two alloys.
The electrochemical behavior of high nitrogen stainless steel (HNS) in 1 mol/L NaCl solution with different pH values was investigated by means of potentiodynamic polarization curves, electrochemical impendence spectrum and current-time transient curves. The results show that anodic passivation of HNS could occur in alkaline solutions, while the corrosion rate of HNS decreased with the increasing pH value; a porous film might be grown on HNS in neutral NaCl solution due to the companying processes of dissolution and repassivation. In acidic and alkaline NaCl solutions, the formed passive films on HNS exhibit superior protectiveness rather than that in neutral NaCl solution.
Micro-arc oxidation coating on 6061 aluminum alloy was prepared in a Na2SiO3 containing electrolyte by a constant current control mode, and the effect of current density on the microstructure and performance of micro-arc oxidation ceramic coating was studied by a series of tests. Results for the above coatings show that their thickness and surface roughness increase with the increasing current density, however, their corrosion resistance decrease, and their hardness increases first and then decreases with the increasing current density. The ceramic coatings are mainly composed of α-Al2O3 and γ-Al2O3. As a comparison, a novel current control method was adopted to prepare a micro-arc oxidation coating. Accordingly, the amount of micro-cracks was significantly reduced, and the corrosion resistance was obviously enhanced for the coating prepared by the new mode.
利用慢应变速率拉伸 (SSRT) 的方法研究了奥氏体不锈钢AL-6XN，316Ti和TP-347在550/650 ℃，25 MPa的超临界水环境中的应力腐蚀开裂敏感性。结果表明，随着温度由550 ℃升高到650 ℃，其屈服强度和抗拉强度均发生了明显的下降，而三者的延伸率却呈现出了3种不同的变化规律。由试样的断口和侧面形貌可知，AL-6XN在550/650 ℃，316Ti在550 ℃工况下具有应力腐蚀开裂倾向，且其应力腐蚀开裂倾向大小关系为：AL-6XN/550 ℃＞316Ti/550 ℃＞AL-6XN/650 ℃。
The susceptibility to stress corrosion cracking (SCC) of several austenitic stainless steels AL-6XN, 316Ti and TP-347 in supercritical water at 550 ℃/25 MPa and 650 ℃/25 MPa respectively was studied by slow strain rate tensile test (SSRT). The strain-stress curve shows that the strength of these three steels decreases as temperature increases; the change in the fracture elongation of them shows different characteristics. The ex-situ scanning electron microscopy (SEM) observation shows that AL-6XN at 550 ℃and 650 ℃, and 316Ti at 550 ℃ exhibit a tendency of susceptibility to SCC, and the tendency of susceptibility to SCC of the three steels may be ranked as: AL-6XN/550 ℃＞316Ti/550 ℃＞AL-6XN/650 ℃.
采用动电位极化曲线、循环极化曲线研究了固溶温度对904L不锈钢在浓硫酸溶液中电化学性能的影响。结果表明，固溶温度对阴极的电化学行为影响不大，对阳极极化曲线则有较大的差异。固溶温度为1120 ℃，保温时间为0.5 h时，904L不锈钢的耐蚀性最好。
Electrochemical performance was studied for 904L stainless steel after solution treatment at different temperatures in concentrated sulfuric acid by means of measurements potentiodynamic polarization curve and cycle polarization curve. The results show that the solution temperature has little effect on cathodic process, but varies the anodic polarization curve greatly. Whilst 904L stainless steel shows the best corrosion resistance after solution treatment at 1120 ℃ for 0.5 h.
使用铝合金在硼-硫酸-草酸电解液中阳极氧化制备有序多孔层。初步探讨了恒流和降压阳极氧化过程膜层生长机理，采用扫描电镜 (SEM) 观察膜层微观形貌，结合电化学阻抗和动电位极化曲线研究不同阳极化工艺制备膜层试样在3.5%NaCl溶液中的耐蚀行为。结果表明，采用三段变压方式制备的阳极氧化膜表面孔密度降低，孔壁增厚，孔径为10~13 nm。疏孔膜层的电化学行为表明孔壁及膜层厚度增大能提高试样电荷传递电阻和耐蚀性能。
A well ordered porous oxide film on aluminum alloy was prepared by a three-stage process in electrolyte of boric-sulfuric-oxalic acids. The relevant growth mechanism of oxide film in the processes with modes of galvanostatic and reduced voltage was elaborated. The morphology and microstructure of the oxide films were characterized by scanning electronic microscopy (SEM). The corrosion performance of the films in 3.5%NaCl solution was examined by electrochemical impedance spectroscopy and potentiodynamic polarization curves. The results show that the anodic film exhibits to be regular and dense with pore diameter of 10~13 nm. Moreover, the electrochemical behavior of anodic oxide film could be described as that the impedance and corrosion resistance was increased with the increasing thickness of the film and the cell wall.
在25 ℃下，将铅丹分别浸泡在NaCl，Na2SO4，混合盐溶液以及去离子水中，并对暴露在空气中的CO2及通入自制CO2的结果进行比较。颜色空间坐标L，a，b的变化结果表明，铅丹在Na2SO4溶液中变色最明显，其次是在水中，再次是在NaCl溶液中，变色最不明显的是在混合盐溶液中。且通入CO2时铅丹的变色速率明显高于不通入CO2时，28 d后色差数值最大相差超过2倍。XRD分析结果表明，无论是否通入CO2，铅丹经浸泡后的组成都由Pb3O4转变为PbCO3和PbO2。
In order to study the influence of CO2 on the discoloration of red lead, which was immersed in deionized water, and solutions of NaCl, Na2SO4 and their mixture for 28 days at 25 ℃ while the test liquors are kept either in static atmospheric CO2 or aerated with gaseous CO2, respectively, then the color of the tested red lead was indexed according to the standard of coordinates L, a, b in color space. The results showed that red lead discolored most obviously in Na2SO4 solution, followed by in water, again in NaCl solution, the last in mixed salt solution. During test in the CO2 aerated liquors, the red lead exhibits higher discoloration rates rather than that in the static atmospheric CO2; the maximum difference of color aberration after 28 days for the two series tests was more than 2 times, specially. XRD tests showed that the red lead transformed from Pb3O4 to PbCO3 and PbO2 no matter test in static atmospheric CO2 conditions or test in the CO2 aerated liquors.
通过电化学方法在10 ℃条件下测试了一次Zn-Ag2O电池材料测试过程中使用的锌皮参比电极的性能。在KOH溶液中浸泡10 min后，锌电极能够提供稳定的 (-1555±5) mV左右的参比电极电位，极化曲线的拟合结果显示随时间的延长腐蚀电流没有发生显著的变化，保持在2×10-5 A/cm2数量级，电化学阻抗谱图各阶段容抗弧实部ZRe和虚部ZIm值变化均不大。测试结果表明，锌电极在7 mol/L的KOH溶液中长时间的腐蚀反应速率变化不大，能够提供稳定的参比电极电位，可以作为Zn-Ag2O电池材料测试及某些碱性电解质中电化学测试的参比电极使用。
Electrochemical methods were applied to investigate the performance of zinc reference electrode in Zinc-Silver oxide primary battery at 10 ℃, which was constructed for trial of materials. After 10 minutes immersion in KOH solution, Zn electrode displayed a steady potential around (-1555±5) mV, corrosion current varied little which maintained at 2×10-5A/cm2 order, and resistances ZRe and ZIm in the capacitive arc of the AC impedance altered little. The results indicated that zinc electrode sustained small corrosion rate for long time immersion in 7 mol/L KOH solution, which provided a stable electrode potential and could be used as reference electrode in measurements such as trial of materials in Zinc-Silver oxide battery and other electrochemical tests in alkaline electrolytes.
概括了保温层下腐蚀 (CUI) 的发生机理，从CUI的防护角度出发，结合工程实际，系统介绍了CUI的防护工艺和防护措施，围绕防护涂层的选择和使用，对CUI防护的研究现状进行了阐述。