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[求助]
翻译成中文，其中一些数字及单位可不管
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After 24 h of free corrosion, the impedance was lowest in the sample without pigment, which reveals the higher activity of this system, and another time constant appeared at the high frequencies. Fitting of the spectra was made using the equiv-alent circuit in Fig. 8, where the high frequency impedance (1 kΩ cm2) is due to the electrolytic solution at the scribe.RHF and QHF describe the high frequency process, and Rct and Qdl correspond to the charge transfer resistance and the double layer capacitance, respectively. Finally, a component describing the mass transfer impedance was considered in some cases in order to account for a small tail appearing below 0.1 Hz. The high frequency process had a resistance of 5–10 kΩ cm2, as shown in Fig. 9, whereas the Y0 for this process has a value of roughly 10−8 to 10−5 Fcm−2. This capacitance is too high for a polymer film, which generally has values in the range of 10−10to 10−8Fcm−2.Further, in the presence of chromate Y0 decreases with time, a behaviour that is the opposite to the known evolution of coating capacitance values (which tend to increase due to water uptake). This high frequency time constant can how-ever be explained by the formation of the passivating film, of either chromium hydroxide or zinc phosphate. The formation of this film starts in the first minutes of exposure, possibly with the precipitation of a monolayer, and grows afterwards, during the first 24–48 h. The low frequency process gives Rct = 20–80 kΩ cm2 and is maximum for the chromate. The double layer CPE grows with time, revealing the growth of the active area underneath the coating, i.e., delamination. The ratio of Y0 with and without pigment is roughly 0.1, mean-ing that the loss of adhesion was weaker in samples with pigment. The delamination rate, estimated from the CPE, was minimum in the epoxychromate coating, followed by the epoxyphosphate and finally by the clear coat. This was the same rate that was determined by visual inspection of the samples at the end of the test. The SVET was also used to study the ionic current distribution above the scribed samples, for the three coatings in 0.1 M NaCl. The evolution of the current maps and the current density values have not show any significant differ-ences among the specimens with the various coatings. As an example, Fig. 10 shows SVET measurements of the scribed HDG sample, coated with the clear epoxy paint. In the first 2–3 days of immersion there was a clear separation between the cathode and the anode along the scribe ( Fig. 10 a) and there were no signs of delamination in the micro-video im-age. For longer exposure times, however, the anodic activity along the scribe increased and the signs of cathodic activity disappeared from the map, as delamination progressed away from the scribe ( Fig. 10 b) |
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RXMCDM: 不想应助就算了！ 2014-05-12 09:16:51
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After 24 h of free corrosion, the impedance was lowest in the sample without pigment, which reveals the higher activity of this system, and another time constant appeared at the high frequencies. Fitting of the spectra was made using the equiv-alent circuit in Fig. 8, where the high frequency impedance (1 kΩ cm2) is due to the electrolytic solution at the scribe.RHF and QHF describe the high frequency process, and Rct and Qdl correspond to the charge transfer resistance and the double layer capacitance, respectively. Finally, a component describing the mass transfer impedance was considered in some cases in order to account for a small tail appearing below 0.1 Hz. The high frequency process had a resistance of 5–10 kΩ cm2, as shown in Fig. 9, whereas the Y0 for this process has a value of roughly 10−8 to 10−5 Fcm−2. This capacitance is too high for a polymer film, which generally has values in the range of 10−10to 10−8Fcm−2.Further, in the presence of chromate Y0 decreases with time, a behaviour that is the opposite to the known evolution of coating capacitance values (which tend to increase due to water uptake). This high frequency time constant can how-ever be explained by the formation of the passivating film, of either chromium hydroxide or zinc phosphate. The formation of this film starts in the first minutes of exposure, possibly with the precipitation of a monolayer, and grows afterwards, during the first 24–48 h. The low frequency process gives Rct = 20–80 kΩ cm2 and is maximum for the chromate. The double layer CPE grows with time, revealing the growth of the active area underneath the coating, i.e., delamination. The ratio of Y0 with and without pigment is roughly 0.1, mean-ing that the loss of adhesion was weaker in samples with pigment. The delamination rate, estimated from the CPE, was minimum in the epoxychromate coating, followed by the epoxyphosphate and finally by the clear coat. This was the same rate that was determined by visual inspection of the samples at the end of the test. The SVET was also used to study the ionic current distribution above the scribed samples, for the three coatings in 0.1 M NaCl. The evolution of the current maps and the current density values have not show any significant differ-ences among the specimens with the various coatings. As an example, Fig. 10 shows SVET measurements of the scribed HDG sample, coated with the clear epoxy paint. In the first 2–3 days of immersion there was a clear separation between the cathode and the anode along the scribe ( Fig. 10 a) and there were no signs of delamination in the micro-video im-age. For longer exposure times, however, the anodic activity along the scribe increased and the signs of cathodic activity disappeared from the map, as delamination progressed away from the scribe ( Fig. 10 b) |
2楼2014-05-11 21:49:59
3楼2014-05-12 08:25:44
jiangguofeng
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【答案】应助回帖
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RXMCDM: 金币+1 2014-05-13 13:39:48
RXMCDM: 金币+1 2014-05-13 13:39:48
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仅供参考 不带颜料的样品自然腐蚀24小时之后电阻最低,显示了这一系统的较高活性，另一个时间常数出现在高频段。 使用图8的等效电路进行光谱拟合，其中的高频阻抗(1kΩcm2)归因于划线处的电解液。 RHF和QHF描述高频过程，Rct和Qdl分别对应于电荷转移电阻和双层电容。 最后，表示传质电阻分量有时被认为是为了说明于低于0.1 Hz处出现一个小拖尾的原因。 如图9中所示这种高频过程具有一个5–10 kΩcm2的电阻,而这一过程的Y0约为10?8到10?5 Fcm?2。。 这种电容，通常值为10?10至10?8Fcm?2，对于高分子膜来说过高。 而且，在铬酸盐存在下Y0随时间而减小,一个与已知的涂层电容值变化（这往往由于吸水而增大）相反的特性。 然而这种高频率时间常数可以用或者是氢氧化铬，或者是磷酸锌钝化膜的形成来解释。 这种薄膜的形成始于暴露的第一分钟,也许会有单层的沉淀，后来在最初24–48小时期间逐渐成长。低频过程得出Rct = 2080 kΩ_cm2,为铬酸盐最大值。双层CPE随时间而逐渐加大,表明涂层下活动面积的增加，亦即,剥离。带有和不带有颜料Y0的比值约为0.1,这意味着带有颜料的样品的粘附力的损失较小。由CPE测定,剥离比例最少的是环氧铬酸盐涂层,其次是环氧磷酸盐，最后是透明涂层。这与在试验结束时样品的目测检查测定的结果相同。 SVET也用来对上述划线样品的于0.1 M NaCl中的三个涂层的离子电流分配的研究。 电流图和电流密度值的变化没有显示出各种涂层样品之间任何显着差异。 例如,图10显示涂有透明环氧树脂涂料的划线HDG样品的SVET测定结果。 在浸入开始的2–3当中阴极和阳极之间沿着划线（图10a）有一个明确的分离，在显微视频图像中没有任何剥离的迹象。 然而，暴露时间更长时沿着划线阳极活度持续增加并且阴极活动性有从图上消失的迹象,正如远离划线剥离的发展那样（图10 b） |
4楼2014-05-12 11:08:35
5楼2014-05-12 18:52:56
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