WBE技术研究水线区破损涂层的剥离机制-Ⅱ

应用阵列电极(WBE)联合电化学阻抗谱(EIS)技术,研究了气/液界面水线处破损涂层在3.5%(质量分数)NaCl溶液中的水线区破损涂层剥离行为。对比涂层剥离过程的腐蚀电流密度和阻抗谱分布行为,探讨了破损涂层在水线区的剥离机制。结果表明,涂层破损区和固有缺陷区均能够加速附近涂层阴极剥离过程。水线区破损涂层剥离行为特征为,破损区和固有缺陷区附近涂层首先发生阴极剥离,进而向外部涂层/金属界面扩展。此外,研究发现,破损区位于水线上方和下方时,其推动阴极剥离能力不同,即,加速水线下方涂层剥离作用弱于水线上方区域,致使水线及水线上方涂层剥离速率明显大于水线下涂层剥离速率。其原因显然与阴极剥离区溶解氧含量有关,即富氧区阴极剥离扩展速率大于乏氧区阴极剥离速率。     

应用灰色系统理论预测沥青涂层在土壤模拟液中的寿命

目的基于灰色系统理论预测模型建立涂层腐蚀寿命的预测模型,利用该模型计算不同厚度的无溶剂环氧煤焦沥青涂层在滨海氯盐土模拟液中的涂层寿命。方法采用电化学方法,测定不同厚度无溶剂环氧煤焦沥青涂层涂覆的碳钢在滨海氯盐土模拟液中的交流阻抗值。基于灰色系统理论GM(1,1)模型将滨海氯盐土模拟液中测试的无溶剂环氧煤焦沥青涂料的低频阻抗模值和浸渍时间关系,建立涂层腐蚀寿命的预测模型。结果三种不同厚度无溶剂环氧煤焦沥涂层试样在侵蚀性溶液中浸泡240 d时,低频阻抗模值仍保持在8.3×10~8Ω·cm~2以上,应用预测公式计算的滨海氯盐土模拟液中三种无溶剂环氧煤焦沥涂层低频阻抗模值的实测值与预测值的相对误差小于6.0%,C0.35,P=1,该模型的预测精度好。涂层厚度为200μm的无溶剂环氧煤焦沥青层预测寿命t=781 d,涂层从浸泡初期阶段进入中期阶段。随着涂层厚度的增加,涂层寿命愈长,当涂层厚度为600μm时,其预测寿命达到2926 d。结论所建涂层腐蚀寿命的预测模型表现出较好的拟合精度和预测可靠度。     

剥离涂层下L245管线钢不同缝隙深度处的腐蚀行为

通过电化学测试和宏观形貌分析,研究了剥离涂层下机坪管道用L245管线钢在不同缝隙深度处的腐蚀行为。结果表明：剥离涂层下不同位置L245钢电极自腐蚀电位的大小与缝隙深度有关;距破损点90 mm处钢电极腐蚀速率有先下降后回升而后再下降的显著变化,并且出现了warburg阻抗扩散弧和明显的弥散效应,是该腐蚀体系下缝隙腐蚀最明显的一个点;距破损点90 mm处钢电极表面腐蚀产物层有明显裂纹,150 mm处钢电极表面点蚀情况突出;涂层剥离会造成L245管线钢缝隙腐蚀,在机坪管道防护中应引起重视。     

WBE技术研究水线区破损涂层的剥离机制

应用阵列电极(WBE)和电化学阻抗谱(EIS)技术,研究了破损涂层在3.5%(质量分数)Na Cl溶液中的电流分布及阻抗谱,并根据电流分布和涂层阻抗变化探究了破损涂层在水线区的剥离机制。结果表明:人为破损和涂层固有缺陷均对其附近涂层有加速阴极剥离的作用。浸泡初期,缺陷处涂层最先剥离,此后,涂层剥离主要在破损处和缺陷处附近优先发展。并且在水线作用下,缺陷处附近的涂层剥离向水线方向发展。水线上涂层较水线下剥离较晚,其剥离速率主要受水在涂层中的渗透速率控制。     

氯化钠型融雪剂中复合缓蚀剂的制备及性能研究

采用失重法确定了在18-wt%氯化钠溶液中复合缓蚀剂的主要组分磷酸二氢锌和葡萄糖酸钠。利用极化曲线法和交流阻抗技术来探究复合缓蚀剂有效抑制碳钢腐蚀的机理。研究结果表明:磷酸二氢锌的添加量为60mg/L,葡萄糖酸钠的添加量为160mg/L时的复配效果较好,腐蚀率为0.0296mm/a,缓蚀率可以达到94.15%。极化曲线和交流阻抗测试显示该复合缓蚀剂对碳钢腐蚀具有明显的协同保护效应,是一种阴极型缓蚀剂。     

添加纳米锌粉环痒涂层腐蚀电化学行为

用电化学阻抗谱(EIS)技术研究了添加不同质量 百分比浓度的纳米锌粉环氧涂层的腐蚀电化学行为，并与环氧清漆(不含颜料)涂层的腐蚀电化学行为进行对比.结果表明，添加不同质量百分比浓度纳米锌粉环氧涂层与环氧清漆涂层具有不同的电化学阻抗谱特征.纳米锌粉的添加量对涂层的防护性能有显著影响，添加不同质量百分比浓度纳米锌粉环氧涂层防腐蚀性能的优劣顺序为：环氧清漆涂层>20mass%>10mass%>2mass%纳米锌环氧涂层.添加纳米锌粉对环氧涂层的防护性能有2方面的影响：一方面使涂层中的微观缺陷大大增多，涂层的防护性能降低；另一方面，由于锌粉的腐蚀产物可将涂层中部分缺陷堵塞，从而对涂层的防护性能有提高作用.由于在所研究的质量百分比浓度范围内(2mass%～20mass%)，前者起了主导作用，所以综合作用的结果是使涂层的防护性能变差.  s.     

酸性土壤中破损防腐层下X80管线钢的应力腐蚀行为

设计加载阵列电极应力腐蚀实验装置,针对我国典型的华南酸性红壤环境,研究高强度低合金(HSLA)X80管线钢在破损防腐层(涂层)模拟缝隙下的应力腐蚀开裂(SCC)行为及影响因素,采用电化学阻抗谱(EIS)监测加载电极的腐蚀电化学过程,利用微电极监测防腐层剥离区局部电位和p H值变化,探讨破损涂层下HSLA管线钢SCC行为和规律.结果表明,防腐层开放破损(漏点)处管线钢发生严重腐蚀:不受力试样表面以阳极溶解占主导的均匀腐蚀为主,而拉伸试样表面出现大量微裂纹和点蚀坑,且沿试样划痕优先生长;封闭的剥离区内部管线钢的腐蚀程度显著减缓.同时,对涂层破损点及剥离区深处管线钢的腐蚀现象和过程进行了讨论.     

交变压力对无溶剂环氧涂层在模拟超深海环境下的电化学行为

通过EIS和LEIS对环氧粉末涂层和无溶剂环氧液体涂层分别在模拟超深海环境中0.1～20和0.1～30 MPa交变压力腐蚀环境下浸泡480 h的失效行为进行了研究,分析了超深海交变压力对涂层耐腐蚀性能的影响,并利用SEM观察了浸泡后涂层/Q345钢界面的表面形貌。研究表明,两种涂层在0.1～30 MPa交变压力作用下涂层的失效过程较为明显,环氧粉末涂层在0.1～30和0.1～20 MPa交变压力浸泡480 h后涂层阻抗值分别下降了2个和1个数量级,无溶剂环氧液体涂层在同样环境下浸泡后阻抗值分别下降了3个和2个数量级,说明了环氧粉末涂层在交变压力条件下对Q345的保护性能更优,阻绝离子渗透能力更强。从LEIS结果分析出在较高交变压力下,涂层微观局部腐蚀扩散速率更快。     

阴极保护电位对破损环氧涂层阴极剥离的影响

采用电化学阻抗技术(EIS),并结合SEM,EDS和XRD研究了室温、静态模拟海水中不同保护电位对海洋平台研制钢在模拟海水中防腐涂料与阴极保护联合作用效果以及对破损环氧防腐涂层的阴极剥离机理。结果表明:在本实验选择的保护电位中,随着电位的负移,涂层剥离面积逐渐增大。-750 mV (vs SCE,下同)保护电位对于破损涂层的金属基体欠保护。-1050 mV电位极化下发生严重的析氢现象,破坏了钙质沉积层的完整性,界面碱化程度较大,涂层剥离面积最大;-850和-950 mV保护电位均能抑制破损处金属的腐蚀;-950 mV保护电位下生成的CaCO_3和Mg(OH)_2钙质沉积层完整致密,保护效果最佳。     

介孔分子筛纳米微容器装载缓蚀剂对环氧涂层防腐蚀性能的影响

目的 研究添加装载缓蚀剂的介孔分子筛对环氧涂层防腐蚀性能的影响。方法 通过浸渍法分别添加有机缓蚀剂葡萄糖酸锌和无机缓蚀剂硝酸铈对介孔分子筛MCM-41改性获得缓蚀颗粒,将缓蚀颗粒与环氧涂层混合获得具有自修复功能的复合环氧涂层。通过中性盐雾试验、电化学交流阻抗谱和局部电化学交流阻抗谱测试,评价了复合环氧涂层的防腐蚀性能,并通过光学显微镜对腐蚀后形貌进行了观察。结果 当缓蚀颗粒含量为5%时,浸泡50 d后,环氧清漆的涂层电阻从9.93×10⁴ Ω降至3.71×10⁴ Ω,而铈改性复合涂层的电阻从2.33×10⁵ Ω降至1.06×10⁵ Ω,其变化趋势更稳定且阻抗值更大,有机锌盐改性复合涂层在浸泡后的起泡现象也得到了明显改善。缓蚀颗粒含量较多(10%)时,复合涂层中的微孔缺陷含量增高,同时引起渗透压的改变,使得腐蚀介质更易渗透至金属基体表面,加速腐蚀的发生。在带缺陷涂层中,两种改性涂层缺陷周围测得的阻抗值呈现先减小后增大的趋势,涂层均出现自修复现象。结论 适量装载缓蚀剂介孔分子筛颗粒的加入,有效地提高了环氧涂层的防腐蚀性能。Zn²⁺/Ce³⁺在缺陷处形成难溶化合物阻碍腐蚀反应是提高涂层防腐蚀能力的主要原因。     

1,4-丁炔二醇缓蚀剂在环氧涂层中的缓蚀机理研究

用电化学方法和红外光谱技术研究了1,4-丁炔二醇缓蚀剂在环氧涂料中缓蚀作用.结果表明:缓蚀剂的加入可以明显改变涂层的阻抗,当缓蚀剂加入量小于0.5mass%时,涂层的阻抗随着缓蚀剂量的增多而增大;对所测得的缓蚀涂层的交流阻抗数据进行拟合并结合红外光谱分析认为,在基底和涂层之间生成了一层不完整的聚合物覆盖膜,在此基础上采用电化学技术探讨了此覆盖膜在涂层中的缓蚀机理.     

钛酸酯偶联剂对纳米Ti粉在环氧树脂中分散性的影响

研究了几种分散剂对Ti纳米粉在环氧树脂中的均匀分散性.其中JN-114钛酸酯偶联剂可使Ti纳米粉均匀分散.同时,应用EIS交流阻抗测试方法测试了不同JN-114添加量的涂层的阻抗值.添加量在5%（以纳米粉w/w计）时的阻抗值最高,且Ti粉可均匀分散.Ti纳米粉分散均匀可加强Ti纳米粉与环氧树脂之间的相互作用,从而改善涂层耐腐蚀性.     

Corrosion behaviour of nano structured sol-gel alumina coated 9Cr-1Mo ferritic steel in chloride bearing environments

A stable boehmite sol was synthesized using Al-isopropoxide as a precursor in an appropriate ratio with water. Afterwards, the 9Cr-1Mo steel specimens were coated with prepared boehmite sol by dip coating technique. AFM analysis of the coated specimens confirmed the presence of nano sized particles (8-12 nm) in the coating. Electrochemical measurements like potentiodynamic and potentiostatic polarisations, electrochemical impedance spectroscopy (EIS) in different concentrations of Cl⁻ ions indicated that the sol-gel alumina coating is able to make an appreciable improvement in the corrosion resistance of the base alloy. It was also observed that the sol-gel coatings can control the pitting attack up to a certain extent in 100 ppm Cl⁻ containing solution. However, the coatings become susceptible towards pitting attack in 200 ppm Cl⁻ bearing solution. The SEM micrographs of the corroded surfaces revealed the occurrence of severe pitting on the uncoated specimens in 100 ppm Cl⁻ solution and also on the coated specimen in 200 ppm Cl⁻ solution.     

富镁涂层对LY12铝合金点蚀的抑制作用

通过动电位极化使LY12铝合金表面产生点蚀后分别涂刷富镁涂层和环氧涂层,利用电化学阻抗等方法研究了富镁涂层对于铝合金基体点蚀的作用。结果表明:富镁涂层使铝合金的开路电位发生明显的负移,并在较长时间保持稳定,基体发生腐蚀的时间显著延迟,说明富镁涂层对于铝合金具有明显的阴极保护作用;点蚀的存在使得富镁涂层中的镁粉溶解速率加快,能更有效地保护基体;富镁涂层试样的铝合金基体浸泡后点蚀无明显的发展,说明富镁涂层能够一定程度上抑制铝合金表面点蚀的生成及发展。     

淡水舱涂层在不同水环境中的失效行为研究

利用附着力测试、吸水率测试和电化学阻抗谱测试等手段,研究了淡水舱涂层在反渗透水、调质水、自来水等淡水以及盐水中的腐蚀失效行为.结果 表明,自来水比盐水具有更快的渗透速度,导致涂层在淡水中会优先失效.淡水舱涂层在反渗透水、调质水和饮用水3种淡水中的腐蚀失效历程相同,根据电化学阻抗谱的变化特征可分为3个阶段:水的快速渗透、...     

The long-term corrosion performance and adhesion properties of 7B04 aluminum alloy/anodic film/epoxy primer system in acidic NaCl solution

The deterioration process and corrosion protective effect of 7B04 aluminum alloy/anodic film/epoxy primer system in acidic NaCl solution for 3024 h were investigated by optical/electron microscopes, electrochemical impedance spectroscopy (EIS), scanning Kelvin probe (SKP), and pull-off adhesion test. The results showed that the protective system of anodic film and epoxy primer can protect aluminum alloy from pitting corrosion after immersion for 2352 h. According to the response characteristics of EIS and SKP, different stages of the failure process could be identified. During the first 100 h of immersion, the water transport in the coating followed Fickian law, and the water diffusion coefficient was 2.03 × 10^?11 cm²/s, which demonstrated that the coating has good impermeability. Anodizing and coating treatment improved the open circuit potential and impedance of 7B04 aluminum alloy and made the distribution of Volta potential more uniform. The decreasing rate of wet adhesion strength was first fast and then slow, which was similar to the variation rule of coating resistance. The anodic film enhanced the adhesion between epoxy primer and substrate so that the failure nature of the adhesion test was mainly the cohesive failure of the epoxy primer.     

Studies on corrosion-resistant behavior of siliconized epoxy interpenetrating coatings over mild steel surface by electrochemical methods

Solvent-free siloxane-modified epoxy coatings were developed by the interpenetrating technique using epoxy resin as base (DGEBA, GY 250, Ciba-Geigy) and hydroxyl-terminated polydimethylsiloxane as modifier (commercially known as silicone) with γ-aminopropyltriethoxysilane as cross-linker, dibutyltindilaurate as catalyst, and 25% zinc powder as additive. Hexamethylenediamine (Aldrich) and polyamidoamine (HY 840, Ciba-Geigy) were used as curatives for the siliconized epoxy coatings containing 25% zinc powder. The corrosion-resistant behavior of these coating systems is assessed by electrochemical methods such as electrochemical potential measurements, potentiodynamic polarization, and electrochemical impedance spectroscopic methods. Based on the results obtained from the electrochemical potential measurements for epoxy and siliconized epoxy coating systems, few samples, namely AX₄ and BX₄, have been found to be the best corrosion-resistant coating systems, and they are used for potentiodynamic polarization measurements, electrochemical impedance, and salt-spray tests. The experimental results reveal that the siloxane (10%) modified epoxy coating system (AX₄) with 25% zinc powder cured by hexamethylenediamine offers the maximum corrosion protection to the steel surface rather than the polyamidoamine-cured system (BX₄). The better protective action offered by the coating system (AX₄) is mainly imparted by the reaction of aliphatic amine hydrogens with oxirane groups of the epoxy resin, which gives coating films with a high cross-link density. The observation is further supported by a capacitive behavior in the Nyquist plot and no spreading of visible corrosion product in the salt-spray test.     

Enhanced corrosion resistance of porous NiTi with plasma sprayed alumina coating

In this study, corrosion behaviour of porous NiTi modified by plasma sprayed alumina coating has been investigated. Scanning electron microscopy and X-ray diffraction techniques were applied for the morphology and microstructure characterisation, while linear sweep voltammetry and electrochemical impedance spectroscopy were used for investigation of corrosion behaviour of coated and uncoated NiTi specimens. Induced couple plasma was conducted to measure ion release of the specimens in simulated body fluid at 37°C. The plasma sprayed Al₂O₃ coating on the porous NiTi improved the surface characteristics for biomedical applications. The alumina coating significantly hampered Ni ion release from the surface. In spite of slight decrease in corrosion resistance of the coated specimens, the corrosion mechanism changed from pitting to general corrosion. The breakdown phenomenon was not detected in the coated specimens, as well. Overall, it can be concluded the longevity of the coated specimen in the simulated biological system was enhanced, comparing to bare NiTi specimens.     

一种新型长效纳米环氧涂料的电位-电容行为研究

采用电位-电容法及Mott—Schottky分析法研究了一种新型长效纳米环氧涂料在5％Na2SO4溶液浸泡过程中的导电行为转变。研究表明，该种新型长效纳米涂料具有非常好的防护阻隔效果。随着浸泡时间的延长，该涂料在失效过程中也存在半导体导电特征。     

Bioactive glass nanopowder and bioglass coating for biocompatibility improvement of metallic implant

Preparation and characterization of bioactive glass nanopowder and development of bioglass coating for biocompatibility improvement of 316L stainless steel (SS) implant was the aim of this work. Bioactive glass nanopowder was made by sol–gel technique and transmission electron microscopy (TEM) technique was utilized to evaluate the powders shape and size. The prepared bioactive glass nanopowder was immersed in the simulated body fluid (SBF) solution at 37 °C for 30 days. Fourier transform infrared spectroscopy (FTIR) was utilized to recognize and confirm the formation of apatite layer on the prepared bioactive glass nanopowder. Bioactive glass coating was performed on SS substrate by sol–gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) techniques were used to investigate the microstructure and morphology of the coating. Electrochemical polarization tests were performed in physiological solutions at 37 °C in order to determine and compare the corrosion behavior of the coated and uncoated SS specimens. Cyclic polarization tests were performed in order to compare the pitting corrosion resistance of the coated and uncoated SS specimens. The results showed that the size of bioactive glass powder was less than 100 nm. The formation of apatite layer confirmed the bioactivity of bioglass nanopowder. Bioactive glass coating could improve the corrosion resistance of 316L SS substrate. Bioactive glass coated 316L SS showed more pitting corrosion resistance in compare with pristine samples. It was concluded that by using the bioactive glass coated 316L SS as a human body implant, improvement of corrosion resistance as an indication of biocompatibility and bone bonding could be obtained simultaneously.