有机涂层/金属腐蚀无损检测技术研究进展

综述了4种有机涂层/金属体系无损检测技术(包括交流阻抗谱、X射线检测、脉冲涡流检测和超声波检测)的基本原理、使用方法和研究进展,指出了有机涂层腐蚀检测方面目前存在的问题,展望了无损检测技术的发展趋势。     

盐雾对环氧涂层防腐蚀性能影响的电化学研究

制备了新型环氧富锌、环氧铁红、环氧云铁3种有机涂层材料。在此基础上，采用交流阻抗技术，对各种环氧涂层在盐雾前后进行了阻抗谱测定，并研究了涂层在盐雾环境中的失效机理。结果表明：3种涂层材料在盐雾实验后，阻抗圆直径均大幅减小，涂层耐腐蚀性能较盐雾前降低。盐雾实验后各涂层的耐腐蚀性能由强到弱依次是环氧云铁、环氧铁红、环氧富锌。通过对盐雾实验前后涂层阻抗谱的分析，比较了几种涂层材料的性能，提出了可能的腐蚀破坏机制。     

利用电化学阻抗谱和电化学噪声分析薄有机涂层的腐蚀过程

电化学阻抗谱与电化学噪声是方便、有效的监测有机涂层腐蚀破坏的测试技术,EIS数据能够反映出涂层破坏机制的变化,而电化学噪声数据处理简单.本实验在一个改进的电解池中对同一涂层同时进行电化学阻抗谱和电化学噪声的监测,结果发现:对于薄的聚氨酯和环氧/聚酰胺涂层,谱噪声电阻R0/sn(f→0)与噪声电阻Rn在涂层腐蚀破坏过程中的发展趋势基本一致,但R0/sn(f→0)小于Rn值;同时,腐蚀反应的极化电阻Rt与噪声电阻Rn的值更接近,变化趋势也基本相同.     

聚氨酯涂层在3.5%氯化钠溶液浸泡作用下的失效机理

采用电化学交流阻抗谱研究了聚氨酯涂层在3.5%氯化钠溶液浸泡作用下的性能变化,用FTIR对涂层失效前后的组成进行了分析,用SEM研究了涂层表面形貌变化,用能谱研究了腐蚀产物的成分,对聚氨酯涂层在腐蚀环境中的失效机理进行研究和分析。     

某有机涂层在盐雾环境下性能分析

在Q235基体上制备有机涂层,利用交流阻抗(EIS)测试、SEM(扫描电子显微镜)分析及涂层结合力测试等方法探讨了涂层在盐雾环境下的腐蚀防护性能。结果表明,腐蚀介质到达涂层/基体界面前,有机涂层的耐蚀性能优异,到达基底后涂层阻抗数值急剧减小;经1 200 h SST(盐雾试验)后,涂层内有大量孔隙及裂纹缺陷生成,但涂层与基体的结合强度仍然较高;根据实验结果提出了相应的特征等效电路。     

聚酯粉末涂层在工业污染环境中的腐蚀行为研究

采用金相显微镜和交流阻抗谱研究了涂层缺陷以及不同前处理工艺对建筑铝合金6063在0.04 mol/LNa2SO4溶液(pH=3.0)中的腐蚀行为。研究结果表明:未经铬酸钝化处理的铝合金缺陷粉末涂层在0.04 mol/L Na2SO4(pH=3.0)溶液中浸泡50 d后,其划痕处堆积满腐蚀产物,划痕两侧局部出现明显翘起和气泡;浸泡相同时间的经铬酸钝化处理的铝合金粉末涂层其腐蚀速率低约1个数量级,铝合金钝化膜能延缓腐蚀,提高缺陷涂层和完整涂层的阻抗。     

喷涂聚脲应用于悬索桥主缆防护涂层的耐腐蚀性能研究

应用电化学阻抗谱技术(EIS)研究了处于模拟海洋环境中的镀锌涂层钢绞线、镀环氧涂层钢绞线、热挤高密度聚乙烯(HDPE)套防护钢绞线和喷涂聚脲涂层钢绞线在干湿交替环境中涂层的腐蚀程度。研究结果表明:镀锌涂层和镀环氧涂层的涂膜阻抗值均在涂层失效阻抗106Ω·cm2之下,涂层已经处于腐蚀后期;HDPE防护层的涂膜阻抗值的数量级为106,涂层即将进入腐蚀后期;喷涂聚脲防护层仍具有较大阻抗,防护性能良好。     

16MnR钢表面复合涂层耐蚀性的电化学阻抗谱研究

在16Mn R钢上用电弧喷涂制备了铝涂层,然后涂装了纳米环氧涂层体系作为其封闭涂层。通过电化学阻抗谱(EIS)和浸泡试验研究了铝/纳米环氧封闭复合涂层在3.5%Na Cl溶液中的耐蚀性以及防护机制。复合涂层体系对基体的保护过程可以分为4个阶段:介质渗入有机涂层阶段,铝涂层与介质接触阶段,铝涂层腐蚀产物形成屏蔽层阶段,以及腐蚀产物渗透封堵有机涂层孔隙阶段。腐蚀介质不断渗透到有机涂层的孔隙,使其体积膨胀,孔隙增大,导致涂层电阻Rc随浸泡时间延长而减小。     

电化学方法研究有机涂层中锌铬黄防锈机理

采用交流阻抗、动态恒电位极化曲线和腐蚀电位时效变化测量等电化学技术，研究了有机涂层中锌铬黄防锈机理。研究结果表明，在５％ＮａＣｌ水溶液中，锌铬黄作为阴极缓蚀剂起防锈作用。试验也表明，用电化学方法研究有机涂层的防锈机理可行。     

铝锌系阳极型强屏蔽涂层电化学阻抗谱分析

利用电化学交流阻抗方法研究了铝锌阳极型强屏蔽涂层的电化学阻抗谱特征。通过对涂层交流阻抗图谱解析，提出其特征等效电路；讨论了阻抗谱特征变化与铝锌涂层结构及性能变化的关系，探讨铝锌阳极颜料在涂层中的作用机理。     

Mixed metal oxide inorganic/organic coatings

Mixed metal oxide ceramer coatings were developed using linseed oil as the organic phase with titanium i-propoxide, and zirconium n-propoxide as the inorganic sol-gel precursors. The overall goal of this study was to develop a primer that will provide corrosion protection and better adhesion to metal substrates with minimal environmental impact. Zinc acetate dihydrate was introduced to the system as an anticorrosive agent. Various coatings properties such as adhesion, hardness, impact resistance, flexibility, and tensile properties were investigated as a function of sol-gel precursor type and content. In addition, electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion properties of these mixed metal oxide inorganic/organic coatings. Department of Polymers and Coatings, Fargo, ND 58105.     

Study of degradation of organic coatings in seawater by using EIS and AFM methods

In this article, electrochemical behaviors and their topography observation for four organic coatings used in seawater, by using both electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) methods to study environment behaviors of different coatings as well as the effects of their film formation, pigments, and fillers on anticorrosion behaviors, were measured. The results show that polyurethane, epoxy, and chlorinated rubber coatings all present one capacitive loop in their tested EIS which contains phenomenally only one time constant, whereas alkyd coating presents two capacitive semicircle arcs. With two capacitive loops, the capacitive semicircle in the high frequency range represents barrier layer property, but the semicircle in the low frequency range represents corrosion reaction of metals under the film. Polyurethane coating used in seawater has well anticorrosion property in seawater immersion test. The appearance features of different layers are visible different between different layers of tested coatings at their surface topography. The property of polyurethane paint film coated on metal is better than other layers, and film of alkyd coating has many pits at its surface by observing the layer's images. AFM photos imaged have also been used to further detail surface topography for four organic coatings, and to approve effects of topography of these coatings on its electrochemical behaviors, from two views of both height and phase modes. It is beneficial to explain deeply the environment behaviors and degradation mechanism of organic coatings. To further study failure of these organic coatings and dynamic processes of corrosion of metal under the film, two equivalent circuit models, according to these tested EIS, have been suggested to explain the corrosive kinetics of these four coatings. To polyurethane, epoxy, and chlorinated rubber coatings used in seawater which have good protection effects for substrate metal, the diffusion process for water, from their layer's surface to interface of film/metal, is mainly controlled factor for degradation. However, the electrochemical reaction process has may become a control procedure for corrosion of alkyd coated metal. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

涂层防护性能的测试方法研究

通过介绍无机涂层的防腐机理,对涂层/金属体系性能和失效过程进行了探讨。系统阐述了无机涂层的测试方法和技术,重点分析了电化学阻抗谱法(EIS)在评价涂层性能中的应用,为进一步研究无机涂层腐蚀的本质和过程提供了有价值的参考。     

Corrosion protection behaviour of sol–gel derived N,N-dimethylthiourea doped 3-glycidoxypropyltrimethoxysilane on aluminium

The present work describes the anticorrosion features of inhibitor doped sol–gel coating on Al metal. Sol–gel coatings were prepared by using 3-glycidoxypropyltrimethoxysilane (GPTMS) as parent precursor. In order to improve the corrosion resistance property of coating, N,N-dimethylthiourea was added into the sol–gel matrix. The corrosion inhibitor doped sol–gel coating on metal was characterized by Fourier transform infrared analysis (FTIR) and scanning electron microscope (SEM). Inhibition effect of N,N-dimethylthiourea doped GPTMS coating on Al substrates in 1% NaCl solution was investigated using electrochemical impedance (EIS) and polarization studies. EIS results showed that the corrosion resistance of sol–gel coating significantly improved upon addition of N,N-dimethylthiourea. The study had outlined the nuances of doping an organic inhibitor to enhance the protection ability of sol–gel coating on Al metal.     

饮料金属包装实罐产品的腐蚀检测

为了检测饮料金属包装实罐产品的腐蚀情况,研制了适用于罐体产品腐蚀监测的电化学传感器,并研究了传感器在某功能饮料中的有效测试面积。应用所研制的传感器对服役期分别为1个月、3个月,27个月,43个月(编号分别为s1,s2,s3,s4) 的四个功能饮料实罐产品进行了电化学阻抗谱(EIS)测试和电化学噪声(EN)测试。EIS结果表明,实罐s1的EIS尚未发展成为两个容抗弧的特征,涂层电阻值大于108Ω?cm2,表明涂层防护性能良好;实罐s2,s3和s4的EIS均呈现双容抗弧特征,涂层电阻值均小于108Ω?cm2,表明该有机涂层失去了防护性能。EN结果表明：s3和s4电流噪声的暂态峰的数量相比s1和s2多,幅值增大,表明局部腐蚀敏感性增加。电化学测试结果表明4个实罐的性能不同,且与服役期有关,因此所研制的传感器可以进行实罐性能检测,并为评估金属包装产品的货架寿命提供科学依据。     

Studies of the impedance models and water transport behaviors of cathodically polarized coating

Cathodic protection (CP) is usually combined with organic coatings to protect metallic structures exposed to seawater. However, the application of CP would enhance coating failure, such as cathodic delamination. To date, there has been few works characterizing the impedance models and water transport behaviors of cathodically polarized coating. In the present article, the analyses of impedance models and water uptake processes of chlorinated rubber coating subjected to various levels of cathodic protection were studied during coatings aging process by electrochemical impedance spectroscopy (EIS).Four distinguished electrical equivalent circuits (EEC) were used to fit the EIS plots of coatings without CP, while only two were employed for samples with CP. Since no corrosion was expected to take place at the metal/coating interface for sample which was polarized cathodically. Coating capacitance was used to investigate the sorption characteristic of water in coating since the increase of C_c was associated with water penetration into the coating. Compared with the sample without CP, those coating systems under CP have a smaller water diffusion coefficient and a further water uptake process after the saturation period.     

Electrochemical impedance spectroscopy as a tool to measure cathodic disbondment on coated steel surfaces: Capabilities and limitations

The disbondment of protective organic coatings under excessive cathodic protection potentials is a widely reported coating failure mechanism. Traditional methods of evaluating cathodic disbondment are based on ex situ visual inspection of coated metal surfaces after being exposed to standard cathodic disbondment testing conditions for a long period of time. Although electrochemical impedance spectroscopy (EIS) has been employed as an effective means of evaluating various anti-corrosion properties of organic coatings; its application for assessing the cathodic disbondment resistance of coatings has not been sufficiently exploited. This paper reports an experimental study aimed at developing EIS into a tool for in situ measurement and monitoring of cathodic disbondment of coatings. A clear correlation between EIS parameters and the disbonded coating areas has been confirmed upon short term exposure of epoxy-coated steel electrodes to cathodic disbondment conditions; however the degree of this correlation was found to decrease with the extension of exposure duration. This observation suggests that EIS loses its sensitivity with the propagation of coating disbondment, and that in order to achieve quantitative determination of the coating cathodic disbondment localized EIS measurements are required to measure the parameters related to local disbonded areas.     

EIS方法对有机涂层在海水介质中的耐腐蚀性研究

运用电化学阻抗图谱(EIS)实验方法,对不同种类的有机涂层在海水介质中的耐腐蚀性能进行研究。     

EIS study of environmentally friendly coil coating performances

The corrosion protection of metal structures by the application of organic coatings is obtained using complex paint cycles. The metal pretreatment as well as primer, intermediate and top coat are the usual layers composing the protection system. Although chromate pretreatment processes and chromate containing primers are widely used, they require highly toxic chromic acid solutions, with consequent effluent disposal and ecological problems. This fact pushed many research laboratories to develop new chromium-free pretreatments and primer inhibitors. Electrochemical impedance spectroscopy (EIS) proved to be a very useful technique to study the protection properties of the organic coating because of the possibility of evaluating the corrosion process on the metal substrate and to measure the electric and dielectric characteristics of the coating. In this study, new chromium-free pretreatments and new primers containing ecological inhibitors were applied to steel substrates coated using an Al-Zn alloy. The results were compared with those obtained using traditional protection systems. The characterization of the complete system (pretreatment and primer) in sodium sulfate solution clearly showed the different water uptake behavior of the two primers, which highlights the better barrier properties of the one containing phosphate. However the corrosion protection of the primer containing chromates is also due to the inhibitive action of the chromates. Hence such a type of primer better withstands the presence of defects in the coating. Moreover the presence of environmentally friendly pretreatments do not worsen the corrosion protection which appears comparable to that observed when chromatation is employed.     

Electrochemical characterisation of protective organic coatings for food packaging

A very common material for food packaging is steel, in the form of metallic containers (cans), in particular for beverage packaging. The corrosion degradation of the packaging must be carefully controlled, not only because the packaging integrity must be preserved, but also in order to avoid any significant contamination of the food or drink, compromising the flavour. In order to increase the coating performance and the food compatibility, new organic coatings are under development with very high protective properties, with the final aim to increase the shelf life of the product. An electrochemical characterisation is often used to study the protective performance of organic coatings on metal substrate for various applications. Some different coatings for food packaging were considered in the present study, including materials with different chemical composition and different pigments content. The protective properties were quantified using electrochemical impedance spectroscopy (EIS) measurements, comparing the electrochemical substrate activity with electrochemical noise (EN) and scanning Kelvin probe (SKP) measurements. The influence of mechanical deformations on the protective properties was also investigated. The results obtained on the studied coatings confirmed the validity of the electrochemical approach and showed that, in general, the coatings containing pigments (TiO₂) have better performance than clearcoats, while comparing the different polymers, epoxy–phenolic coatings have a better corrosion protection than epoxy–melamine coatings.