柠檬酸对Ni-P合金化学镀沉积速度和镀层性能的影响

研究了柠檬酸浓度对乙酸盐缓冲体系Ni-P合金化学镀沉积速度、镀层含磷量及其耐蚀性与结构的影响，并对镀层在镀态下和经热处理后的耐蚀性与结构进行了比较。结果表明，随柠檬酸浓度的增加，沉积速度先增加后l牵低，而镀层中磷含量则先降低后增加；镀态时高磷合金为非晶态结构且具有较好的耐蚀性，中磷合金则为非晶 微晶结构，耐蚀性较低，而所有镀层经350℃热处理1h后，结构都转变为晶态，且耐蚀性明显提高。     

阴极极化处理微孔铬工艺

一概述机械,电器,日用五金等所用的装饰防护性镀层,国内外普遍采用Cu-Ni-Cr或Ni-Ni-Cr体系,这种体系的发展方向是减薄镀层的总厚度,节约贵重金属,提高镀层的防腐蚀性。由于Cu-Ni-Cr这种复合镀层的电极电位,从上而下都比钢铁基体正,不能起到电化学防护作用。而阳极镀层和腐蚀分散型镀层耐蚀性好。近几年这两种类型的镀层结合成一体,组成高耐蚀性镀层,镀层的总厚度减薄,防腐蚀性能进一步提高。     

化工机械材料的腐蚀分析及防腐蚀研究

介绍了化工机械材料的腐蚀类型,并重点研究了化工机械材料的防腐蚀措施。通过化学镀Ni-Fe-P合金镀层对化工机械材料进行了表面处理。在室温下进行了全浸试验,并测试了极化曲线和电化学阻抗谱,分别从宏观和微观上评价了施镀前后化工机械材料的耐蚀性。结果表明:与施镀前的试样相比,施镀后试样的平均腐蚀速率大幅度降低,自腐蚀电位正移,电荷转移电阻提高了一倍多。这证明了化学镀Ni-Fe-P合金镀层是提高化工机械材料耐蚀性的有效措施。     

金属腐蚀速度的电化学噪声检测:理论模型研究进展

金属材料腐蚀速度的测定是评价材料在服役环境中耐蚀性的重要指标。电化学噪声技术由于其原位无损无干扰的优势,用于金属材料的腐蚀监检测的应用已有50多年的历史,可以实现对金属材料在各种环境下的腐蚀速度和腐蚀形态的评估。目前制约电化学噪声技术应用的关键科学问题之一是如何建立理论模型进而得到表征腐蚀速度的特征参数。目前腐蚀速度评价主要采用噪声电阻或谱噪声电阻来表征,但很多情况下2个参数本身缺乏严格的物理意义。本文综述了目前用于金属腐蚀速度定量分析的3种理论模型(电极过程动力学模型、等效电路模型、散粒噪声理论),并深入讨论了每种模型的优缺点,最后指出了该领域的发展方向。     

轮胎噪声评价指标研究

分析了人听觉系统的特性和轮胎噪声的特点,阐述了用Ｚｗｉｃｋｅｒ响度替代Ａ声级作为轮胎噪声客观评价指标的优点,并对Ｚｗｉｃｋｅｒ响度的Ａ声级两种客观评价指标进行对比试验。结果表明,在评价精度要求下高时可以采用Ａ声级等常规指标进行粗略比较,而Ｚｗｉｃｋｅｒ响度评价结果和主观评价结果能较好吻合,宜作为轮胎噪声客观评价指标。     

非晶Ni-P合金镀层的制备及应力腐蚀研究

为了探究非晶Ni-P合金镀层对304不锈钢应力腐蚀的影响,通过优化工艺配方制备非晶Ni-P合金镀层,并对其结构和耐蚀性进行了分析。结果表明:非晶Ni-P合金镀层表面平整,P的质量分数为10.72%;非晶Ni-P合金镀层的耐蚀性优于304不锈钢的,接近耐腐蚀材料等级;非晶Ni-P合金镀层的应力腐蚀敏感指数更低,起到较好的机械隔离和电化学保护作用。     

非晶态镀层耐蚀性的研究进展

非晶态镀层具有特殊的微观结构，是很好的耐蚀性材料。综述了近几年来国内外在非晶态镀层耐蚀性方面的研究进展。阐述了非晶态镀层的耐蚀机理。镍系合金、铁系合金、钴系合金及铬系合金的耐蚀性及其应用。此外，介绍了复合表面技术在提高非晶态镀层耐蚀性中的应用。     

电镀黑铬太阳能选择性吸收器的热稳定性及耐蚀性(英文)

黑铬作为最具吸引力的太阳能选择性吸收材料之一,已得到实验证实并用于太阳能收集器.本文评价了黑铬太阳能选择性吸收器的热稳定性和耐蚀性.采用三价铬镀液,在铜基体上电沉积了黑铬镀层.另外,采用六价铬镀液制备了六价铬黑铬镀层作为对比.根据ISO/CD 12592.2标准,评价了热处理循环前后镀层的太阳能吸收,发射性能和热稳定性.分别采用扫描电镜和X射线衍射,表征了镀层的微观结构和化学组成.采用分光光度法测量了镀层的吸收率和发射率.结果表明,镀液中的配位剂对镀层的热稳定性有显著影响.与六价铬镀层相比,三价铬镀层具有更优异的热稳定性和耐蚀性.     

装饰防护镀铬工艺的正交试验研究

给出了3Ni-Cr装饰防护镀铬的工艺路线。通过CASS试验检测了镀层的耐蚀性。以耐蚀性为评价标准,采用正交试验优化了工艺,发现各因素中Cr^3＋对镀层的影响最大,且得出了最佳工艺为：170g／L CrO3,1．7g/L Cr^3＋,1．5g/L H2SO4,pH2．5,θ50℃,J15A／dm^2。介绍了工艺的维护与管理,包括控制CrO2与H2SO4的质量比及Cr^3＋的含量,阳极与电源的要求,抑雾剂的使用等。该工艺性能稳定,镀层光亮,致密,平整,耐蚀性高。     

汽车用镁合金超声波辅助化学镀Ni-P-Al_2O_3镀层的耐蚀性

在汽车用镁合金上分别进行常规化学镀和超声波辅助化学镀,制备了两种Ni-P-Al_2O_3镀层。采用扫描电镜和能谱仪对两种镀层的表面质量和化学成分进行了分析,并通过全浸试验和电化学阻抗谱测试分析了两种镀层的耐蚀性。结果表明:两种镀层的耐蚀性都比镁合金基体的耐蚀性好,并且超声波化学镀层的耐蚀性较常规化学镀层的耐蚀性更好。由于超声波作用使得超声波化学镀层的表面质量更好,所以超声波化学镀层表现出良好的耐蚀性。     

硫酸盐还原菌诱导腐蚀的电化学噪声分析

基于电化学噪声(EN)和信号处理研究硫酸盐还原菌(SRB)对304不锈钢诱导的腐蚀。将304不锈钢电极分别置于硫酸盐还原菌接种前后的培养基中,利用电化学工作站分别对2种试样的腐蚀进程进行电化学噪声测量,将测得的噪声数据去除直流漂移,再对这些数据进行时域、频域和小波分析。结果表明:通过时域分析得到的标准偏差和噪声电阻可表征腐蚀速率,局部因子则可以区分腐蚀类型。通过频域分析得到的功率谱密度曲线,能表征304不锈钢腐蚀的程度。小波分析则能从不同尺度下分解信号,更加直观、清晰地表征腐蚀进程。利用电化学噪声技术能很好地监测SRB对不锈钢的腐蚀影响,根据不同的需求采用不同的分析方法进行电化学噪声数据分析,才能准确表征腐蚀类型、腐蚀速率以及腐蚀程度。     

Self Linear Polarization Resistance-Theory and Examples

Measuring the corrosion rate of a corroding metal is of interest in many situations, including monitoring industrial processes and undertaking fundamental research. The corrosion rate of a metal can be measured electrochemically by determining its polarization resistance, which is inversely proportional to the corrosion rate. What is described in this article is a technique for mathematically extracting from electrochemical noise (EN) data the polarization resistance as well as a measure of the frequency of anodic and cathodic transients. The theoretical framework for self-linear polarization resistance is based on a time-domain analysis of an electrical circuit model of an EN experiment. The analysis indicates that the polarization resistance for one electrode can be interpreted only if the second electrode alone is generating current transients during a given time record. One advantage of this approach, compared with other techniques for obtaining a polarization resistance from EN data, is that short time records, i.e. less than one minute, can be assessed. The self-consistency of the polarization resistance can be assessed with a correlation coefficient. Another advantage is that the nature of localized corrosion events can be attributed to either anodic or cathodic current transients from one of the electrodes.     

Investigation on copper corrosion behaviour in industrial waters by electrochemical noise analysis

This paper represents an attempt to apply electrochemical noise analysis to monitor copper corrosion rates in solutions simulating near neutral or acidic industrial waters, containing chloride, sulphate and bicarbonate ions. The very low noise levels characterizing these systems make the evaluation of the noise resistance possible only with a four electrode arrangement, where the electrode couples used to detect the voltage and current fluctuations have different surface areas. This arrangement is probably a handicap to the evaluation of the polarization resistance values from noise resistance data. Cyclic voltammetries were carried out in order to investigate the nature of the corrosion products obtained in solutions with different pH.     

Dimensional analysis applied to pitting corrosion measurements

In this work, two new indices, S_E and S_G are proposed to evaluate pitting corrosion by dimensional analysis of three parameters of PSD, the slope of high frequency linear region (k), the critical frequency (f_c) and the low-frequency plateau level (W). And then they are employed to analyze the potential electrochemical noise obtained during the corrosion processes of stainless steel 1Cr18Ni9Ti and pure Al, two materials most susceptible to pitting corrosion in NaCl solutions. Meanwhile another two mathematical methods, statistics and wavelet transform techniques, are also carried on the same potential oscillation data to estimate the function (meaning) of these two indices (S_E and S_G) in monitoring corrosion processes. The results suggest that, the index S_E is directly proportional to the rapider potential oscillating and higher fluctuation amplitude and can be used to depict the distribution behavior of electrochemical noise, while the index S_G can be used to depict the slower corrosion processes.     

Embedded electrode electrochemical noise monitoring of the corrosion beneath organic coatings induced by ac-dc-ac conditions

The degradation of urethane topcoat/epoxy primer systems used for military aircraft and industrial applications were monitored using the electrochemical noise method and measured with embedded electrodes. The degradation was induced by the ac-dc-ac method. The trend in the noise resistance parameter was consistent with the trend in the low frequency impedance modulus obtained from electrochemical impedance spectroscopy experiments. The localization index was not informative about the corrosion mechanism. However, the two shot noise parameters, average charge of event and event frequency, were able to characterize the corrosion process beneath the coating. There was a change from uniform corrosion to localized corrosion on the metal substrate associated with the aircraft coating as indicated by the decrease in frequency event as this coating failed. There was an increase in the charge per corrosion event of the substrate of the industrial coating indicating that the uniform corrosion occurring became more severe as the coating failed.     

Cl-污染大气环境下T91钢孔蚀萌生的电化学噪声检测

采用电化学噪声(EN)技术研究了T91马氏体耐热钢在Cl^-污染大气环境下的电化学行为,并针对EN数据进行统计分析,得到表征腐蚀萌生和发展的特征参数。运用Thevenin等效电路模型得到统计参数与腐蚀速度之间的关系并用实验数据进行验证。实验结果表明,EN技术可以有效监测大气环境下T91钢的腐蚀过程,电流噪声幅值大小一定程度上反映了局部腐蚀萌生和发展过程。理论分析结果表明,溶液电阻可影响电位噪声和电流噪声的测量以及噪声电阻的计算结果,但只要溶液电阻值远小于工作电极的阻抗,其影响可以忽略。谱噪声电阻不等于研究电极的阻抗模值,二者之间存在一定的关系。实验数据的进一步分析证实了理论预测的正确性。     

Analysis of raw and trend removed EN data in time domain to evaluate corrosion inhibition effects of New Fuchsin dye on steel corrosion and comparison of results with EIS

The inhibition effect of New Fuchsin dye on the corrosion of mild steel in 1 M HCl was studied using electrochemical noise measurements (ENM) and the electrochemical impedance spectroscopy (EIS) method. The experimental results indicated that, the New Fuchsin is effective inhibitor even in very low concentration (5 ppm). EIS studies showed that the polarization resistance of mild steel in 1 M HCl increases as the inhibitor concentration increases. Experimental results showed that the DC trend can affect the results obtained from analysis of electrochemical noise data in time domain. DC trend of electrochemical noise data was removed by MAR method. After trend removal, electrochemical noise resistance is confirmed to be strongly correlated to polarization resistance.     

Study of the copper anode passivation by electrochemical noise analysis using spectral and wavelet transforms

The passivation of copper anode in sulphuric acid industrial electrolyte at 65 °C was investigated by electrochemical noise (EN) technique using three imposed anodic currents 153, 180 and 210 mA cm⁻² (galvanostatic or chronopotentiometric technique). The wavelet transforms and power spectral density (PSD) analyses have been employed to analyse the EN data. It has been found that during active dissolution the electrode surface is dominated by long time scale process and the change of the position of the maximum relative energy from D7 to D8 could be an indication of future passivation. This is associated in fast Fourier transform analyses by the disappearance of the low frequency plateau (white noise). During anodic dissolution the electrode surface was mainly undertaking general corrosion and the relative energy distribution was concentrated on large timescale crystals (D7-D8) with range of scale between 25.6 and 12.6 s. During passivation the electrode surface was dominated by short time scale process (D3), and during trans-passivation by medium (D4) followed by short time scale process (D2) with range of scale between 0.8 and 0.4 s, 1.6 and 0.8 s and 0.4 and 0.2 s, respectively. Crystals D2 and D3 could be related to metastable pitting and crystal D4 to localized corrosion.     

Monitoring of steel corrosion in concrete by electrode arrays and electrical resistance probes

In the present work two relatively new methods were implemented, in order to follow exactly the time and spatial evolution of steel corrosion in concrete. Measuring with a coupled electrode array is by some means the advancement of electrochemical noise (EN) with electrically connected micro-electrodes, which are spatially arranged, the assessment of anodic and cathodic currents distribution in time is possible. An electrical resistance (ER) probe can provide general corrosion rate, which is calculated from the thickness reduction; however, its response to localize corrosion is limited. The measurements were performed in concrete specimens, which were exposed to periodic wetting and drying cycles. The results of both used methods were compared and related to the conditions of the micro-electrodes and the ER probes after the test was finished. It was found that micro-electrode arrays can monitor the time and spatial evolution of steel corrosion in concrete. The measured currents reliable indicate the temporal anodic and cathodic activities of individual electrodes, and the assessment of general corrosion rates is also possible. Two characteristic fluctuations of the measured currents from the micro-electrode arrays were defined: slower fluctuations and shorter transients. It is believed that the slower fluctuations were generated by rather general corrosion of the electrodes, whereas the shorter transients were very probably generated by the initiation of pits. In accordance with the results of our previous study, it was confirmed that electrical resistance probes (ER) are able to measure reliably the cumulative corrosion damage, as well as the average general corrosion rate. The general corrosion rates obtained by using ER probes were generally slightly higher than those estimated from the measured currents. It should be mentioned that due to the relatively short duration of the experiments, the reliability of the methods for long-term practical applications still needs to be assessed.     

Noise resistance and shot noise parameters on the study of IGC of aluminium alloys with different heat treatments

In the present paper, the effect of heat treatment on the susceptibility to intergranular corrosion (IGC) of aluminium alloys is analysed. Samples of aluminium alloys AA2024 and AA7075 were first subjected to different heat treatments. Then the susceptibility of these samples to IGC was determined by means of normalized tests, based on the immersion of the samples in an aggressive medium and the subsequent evaluation of the attack, using metallographic analysis. In order to quantity the IGC suffered by the samples, both the degree and the depth of the attacks were measured. In addition, electrochemical noise (EN) signals were recorded during the normalized tests. This technique is especially interesting for the study of corrosion processes of systems with low impedance, such as those faced in this paper, since it does not modify the corrosion potential of the system. Three parameters were used to analyse the EN signals: noise resistance (R_n) and two shot noise parameters, the characteristic charge (q) and the characteristic frequency (f_n). Finally, the relationship between the results of the metallographic analysis and those obtained from the analysis of EN signals was established. Unfortunately, a poor correlation between the shot noise parameters and the degree of IGC was found, due to both the high localization and high activities of all systems.