有机涂层防护性能与失效评价研究进展

简要综述了近年来评价有机涂层防护与失效的宏观与微观电化学方法。介绍了直流电化学极化、电化学阻抗谱(EIS)、电化学噪声(ENM)等宏观电化学测试方法,此类方法主要反映涂装材料的整体防护特性和老化失效规律;而微区电化学测量方法,如局部电化学阻抗(LEIS)、扫描开尔文探针(SKP)、扫描振动电极(SVET)、扫描电化学显微镜(SECM)和原子力显微镜(AFM)等,主要用于涂层局部或微缺陷的检测,以及界面层物理化学变化规律的研究。简述了应用这些方法所取得的成果,对进一步研究涂层失效具有一定指导意义。     

基于Image-J图像法和电化学法的微弧氧化涂层孔隙率评价

为精确量化和评价微弧氧化(MAO)涂层的孔隙率,在硅酸盐电解液中通过恒压MAO方法于AZ31B镁合金表面制备氧化物涂层。利用线性极化、电化学交流阻抗谱(EIS)和Tafel曲线分别计算涂层的极化电阻并考察其腐蚀防护性能,重点采用Image-J图像法和两种极化电阻比值法评价了涂层孔隙率,提出了适合MAO涂层孔隙率的评价方法。结果表明:当氧化电压由260 V升至290 V时,MAO样品的自腐蚀电流密度由2.8μA/cm~2增加至5.6μA/cm~2。结合线性极化电阻和EIS拟合结果,证实涂层腐蚀防护性能随氧化电压的升高而降低。同时,Image-J图像法计算的表面孔隙率由10.14%增加至11.48%,线性极化电阻计算的通孔孔隙率由3.51%增加至7.08%,表明涂层腐蚀防护性能与其孔隙率呈负相关,即随孔隙率增加而降低。与电化学交流阻抗谱或Tafel曲线所得极化电阻比值法相比,简单的线性极化电阻比值法更适合量化MAO涂层的通孔孔隙率,而Image-J图像法适合通过MAO涂层的表面SEM像量化表面孔隙率及孔径大小的分布情况。     

2A12铝合金表面有机复合涂层的耐蚀性能研究

以氟碳面漆、丙烯酸聚氨酯面漆、环氧玻璃鳞片胶泥中间漆、铝合金防腐底漆和底面合一铝合金专用防腐漆为原料,采用不同的配套方案在2A12铝合金表面制备了有机复合涂层,通过扫描电子显微镜(SEM)、中性盐雾实验、极化曲线测试和电化学阻抗谱(EIS)测试对有机复合涂层的耐蚀性能和耐蚀机理进行了研究。结果表明:有机复合涂层与2A12铝合金基体之间,以及有机复合涂层中各层之间均结合良好;中性盐雾腐蚀30 d后各有机复合涂层仍具有表面光泽,没有出现开裂和剥落;(底漆+中间漆+氟碳面漆)方案的有机复合涂层耐蚀性能最佳,使腐蚀电流密度下降了3个数量级,极化电阻上升了3个数量级,阻抗值提升约2个数量级。     

小波噪声电阻与EIS结合评价涂覆层性能

用电化学阻抗谱和电化学噪声方法研究常用碳钢基底高绝缘性能防护层.在中高频范围测试涂层体系的电化学阻抗谱,在低频范围测试电化学噪声.用电化学阻抗谱中高频信息得到评价参数等效电容.用小波多分辨分析分频特征,建立了小波噪声电阻方法,可以得到较低频率下的噪声电阻信息.得到的评价涂敷层性能的等效电容和小波噪声电阻有很好的对应性.     

基于高频电化学阻抗谱测试的涂层防护性能评价方法

研究了施加掺杂铁红粉的环氧涂层的Al在3.5 mass%NaCl溶液(模拟海洋环境)中的电化学阻抗谱(EIS)随浸泡时间的变化,提出了两种基于高频EIS测试数据的快速评价涂层防护性能方法:局部拟合涂层电阻法和修正的特征频率法。结果表明,虽然局部拟合所得的涂层电阻值与全谱拟合所得值有一定偏差,但它们的变化趋势吻合,且很好反映了涂层的失效过程,说明局部拟合涂层电阻的方法有望被用于涂层防护性能的监检测。此外,针对传统涂层快速评价所用的特征频率法未考虑涂层电容弥散效应的不足,提出了考虑涂层电容弥散效应时特征频率的修正方法。实验观察到,在涂层浸泡过程中涂层电容对应的n值逐渐下降,而修正值与传统特征频率值差别也越来越大,说明在涂层防护性能监检测中对传统特征频率法进行修正十分必要。     

Ti纳米粒子对环氧涂层防护性能的影响

应用电化学阻抗法(EIS)、示扫描量热法(DSC)、X射线光电子谱(XPS)研究了添加Ti纳米粒子对环氧涂层防护性能的影响.结果表明:添加Ti纳米粒子可以提高环氧涂层的防护性能,添加量在0.5%(以w/w计)时最好.这是由于添加Ti纳米粒子虽然可增加涂层孔隙率,但Ti纳米粒子与环氧树脂之间存在的相互作用可改善涂层对腐蚀性介质的屏蔽性能,提高涂层的防护性能.     

镁合金水基金属耐蚀涂层的研究

针对镁合金化学性质活泼、不易直接涂装等特点，研究开发了一种主要由微米金属粉、有机硅烷等组成的新型环保水基金属防护涂层.中性盐雾试验、3.5%NaCl溶液浸泡、电化学阻抗和附着力测试等研究结果表明，该涂层具有良好的结合力、耐热性以及对基体的防护性能.用扫描电子显微镜(SEM)等分析手段研究了涂层的片状层叠组织结构，并探讨了涂层的成膜机理与防护作用.     

2024铝合金化学转化膜与磷化底漆耐蚀性的研究

通过盐雾实验、稳态阳极极化曲线和电化学阻抗谱3种测试方法，对磷化底漆和阿洛丁(1200)化学转化膜进行了测试，结果发现磷化底漆的耐蚀性明显优于阿洛丁化学转化膜．在中性盐雾实验10个周期中，阿洛丁化学转化膜腐蚀明显，而磷化底漆完好如初．在稳态和弱极化区，两者抗蚀性能相似，而在强极化区，磷化底漆明显优于阿洛丁化学转化膜、在电化学阻抗谱上，磷化底漆极化电阻(Rp)比阿洛丁转化膜高1个数量级．     

霉菌对A04-60氨基烘干磁漆的侵蚀作用研究

通过采用霉菌实验、扫描电子显微镜(SEM)、原子力显微镜(AFM)、电化学阻抗谱(EIS)等方法与手段研究了霉菌侵蚀对A04-60氨基漆表面微观形貌、防护性能等的影响,鉴定了侵蚀菌种。结果表明,导致A04-60氨基漆变质的主要因素是黑曲霉,霉菌生长提高了涂层表面粗糙度,表面缺陷不断扩大和深入,使得涂层的阻抗值和防护性能下降。     

镀锌钢表面硅烷掺杂电泳漆涂层的腐蚀电化学行为研究

将γ-(2,3环氧丙氧) 丙基三甲氧基硅烷 (GPTMS) 掺杂到不含颜料的水性环氧树脂中,通过一步电泳法在镀锌钢表面构建得到硅烷掺杂的电泳漆涂层。采用电化学阻抗谱和扫描电化学显微镜技术研究了涂层体系的防护性能,并结合其它手段开展了机理研究。结果表明,有机硅烷的加入能够显著提高环氧电泳漆涂层在腐蚀介质中的防护性能,硅烷掺杂抑制环氧涂层的吸水和溶胀。提出了硅烷掺杂电泳漆涂层的如下防护机理：一方面,GPTMS的掺杂增加了涂层的交联程度;另一方面,电泳过程中促进GPTMS组分在金属与涂层界面的优先沉积形成富集层,从而提高了基体与涂层间的结合力。     

Effect of Si nanoparticles on the corrosion protection performance of organic coating on carbon steel in chloride environment

This work examines the effect of silicon (Si) nanoparticles on the corrosion protection performance of epoxy coating over carbon steel by Electrochemical Impedance Spectroscopy (EIS) and Transmission Electron Microscopy. The EIS was performed in a 0.1 M NaCl solution after a wet/dry cyclic corrosion and continuous immersion test. The addition of Si nanoparticles increased the film resistance (R_f) and the charge transfer resistance (R_ct) of the coated steel. The surface analysis showed that uniform and fine Si-Fe complex oxides layers were formed acting as barrier layers that enhanced the corrosion protection of the coated steel in the wet/dry cyclic corrosion test. The results of the EIS of the coated steel with Si nanoparticles suggested that Si nanoparticles play a beneficial role in enhancing the corrosion resistance of organic coated steel.     

电化学阻抗谱方法研究评价有机涂层

介绍了研究涂层性能的电化学阻抗谱（ＥＩＳ）实验方法以及该方法的在研究,评价有机涂层方面的应用。由于涂层的种类很多,每种涂层的防护机制各不相同,其ＥＩＳ的数学物理模型也各不相同,本文共建立了６种模型（等效电路）来分别处理不同有涂层体系的电化学阻抗谱,介绍了ＥＩＳ数据处理的快速方法－特殊频率法。     

Corrosion inhibition performance of polypyrrole Al flake composite coatings for Al alloys

Polypyrrole (PPy) was deposited on Al flakes in the presence of oxyanions (molybdate, phosphate or vanadate) as inhibiting dopants and the PPy modified Al flakes were incorporated into an epoxy primer as protection pigments for AA 2024-T3. The protection performance of the PPy Al flake coating was assessed by electrochemical evaluations including Scanning Vibrating Electrode Technique (SVET), Electrochemical Impedance Spectroscopy (EIS) and salt spray test. The oxyanion doped PPy Al flake coating shows enhanced protection performance for AA 2024-T3. An oxygen scavenger protection mechanism is suggested for PPy in the composite coating, and the roles of Al flake and oxyanions in the formulation are discussed.     

The effect of copper ion on microstructure,plating rate and anticorrosive performance of electroless Ni-P coating on AZ61 magnesium alloy

In this paper, the effects of copper ion addition on microstructure, composition, deposition rate and anticorrosive performance of electroless Ni-P coating on AZ61 magnesium alloy have been investigated. Deposits were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX) techniques. The corrosion behavior of the deposits was studied by Open Circuit Potential (OCP) measurements and Electrochemical Impedance Spectroscopy (EIS) in 3.5 wt % NaCl. Moreover, the deposition rate of the coatings was determined by polarization tests. The results indicate that introduction of Cu²⁺ improves the characteristics and anticorrosion performance of Ni-P coating.     

Corrosion of magnesium modified with different compounds in chloride solution

The surface of magnesium electrode was coated by immersing in phosphate, tungstate, molibdate and cerium solutions, after polishing with sand paper and abrading in 0.15 M HCl solution for 20 seconds. The corrosion of modificated magnesium with different compounds was investigated by electrochemical methods in 1 M NaCl solution. The results show that phosphate, tungstate, molibdate and cerium cations provide the corrosion protection for magnesium forming insoluble compounds on magnesium surface. The inhibition effect of protective layers prepared on magnesium surface were investigated by using potential-time, current-potential curves and Electrochemical Impedance Spectroscopy (EIS) spectra. The inhibition effect was calculated from corrosion rates and polarization resistance.     

基于电化学阻抗谱的Zn及Zn-Al涂层的自封闭机理研究

目前，热喷涂Zn—Al合金涂层已替代Zn及Al涂层，成为海洋环境下钢结构件腐蚀防护的首选方法。使用高速电弧喷涂和粉芯丝材技术制备了Zn—Al涂层，采用电化学阻抗谱法(EIS)，结合涂层腐蚀产物X-射线衍射(XRD)及涂层腐蚀后表面形貌分析，对比研究了Zn及Zn—Al涂层的耐蚀性，并探讨了涂层的自封闭机理。结果表明，活化溶解是Zn涂层腐蚀的主要机制，在腐蚀过程中Zn涂层表现出自封闭作用，但由于腐蚀产物是疏松的，其自封闭效果微弱；Zn—Al涂层表现出了更好的耐蚀性，涂层表现出一定的自封闭效果。     

Enhanced corrosion protection by powder coatings on hot rolled steel (HRS) for high-temperature applications

Hot rolled steel (HRS) has long been a major product to the motor industry for bodywork, as galvanised steel (zinc coatings), and it is widely used in building and as tinplate (including tin and chrome oxide coatings) for food, etc. can-making. Among more specialist uses its moderate production costs makes it suitable for the manufacturing process. In this study, newly developed corrosion protection enhanced silicone based powder coating was evaluated on hot rolled steel (HRS). The powder coating in this study was developed to withstand high temperatures up to 550°C without any degradation. In the study silicone resin was incorporated with fillers, corrosion inhibitors and fibres at various compositions to achieve maximum heat resistance and improved corrosion resistance. Protective behaviours of the differently formulated powder paints were investigated before and after heat exposure. The developed paint system was evaluated using various test methods such as heat resistance, salt spray, Electrochemical Impedance Spectroscopy (EIS), adhesion test and microstructure study using SEM. The evaluation of test results revealed that powder coating combining zinc dust particles and mineral fibres have better performance due to better corrosion and adhesion stability in the corrosive environment before and after heat exposure up to 550°C.     

Polyoxadiazole-based coating for corrosion protection of magnesium alloy

In this study, polyoxadiazole-based coatings were molecularly designed by attaching two different functional groups, i.e., diphenyl-ether and diphenyl-hexafluoropropane, in the main polymer chain for the purpose of low water permeability and eventually for high corrosion protection of AM50 magnesium alloy. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) were used to evaluate the coating performance of the two polymers. Electrochemical experiments showed that POD-6FP (poly(4,4′-diphenyl-hexafluoropropane-1,3,4-oxadiazole)) coated alloy exhibited 3-4 orders of magnitude higher corrosion resistance as compared to the POD-DPE (poly (4,4′-diphenyl-ether-1,3,4-oxadiazole)) coated alloy. The high coating performance of the POD-6FP polymer can be attributed to the hydrophobic group attached to the polyoxadiazole chain.     

Scratch-resistant anticorrosion sol-gel coating for the protection of AZ31 magnesium alloy via a low temperature sol-gel route

A novel hybrid sol-gel/polyaniline coating has been developed for application onto an AZ31 magnesium alloy for corrosion protection. Electrochemical Impedance Spectroscopy in 3.5 wt% NaCl and diluted Harrison’s solutions, along with salt spray tests showed that the coating possesses excellent corrosion resistance. The hybrid coating was modified by doping with silica nanoparticles (for scratch resistance) and cured at a low temperature of 75 °C. Whilst conventional sol-gel methods tend to limit the coating thickness values up to 10 μm, the new hybrid sol-gel/polyaniline system presented here allows thick coatings to be deposited, in this case, around 50-60 μm.     

Role of thickness on electrochemical behaviour of Ni2Si coatings in NaCl solution

Abstract

Ni₂Si intermetallic coatings were deposited on a substrate of 420 stainless steel using a high velocity oxy-fuel (HVOF) process. The electrochemical corrosion behaviour of the coatings in 3.5% NaCl solution was investigated by means of Tafel polarisation tests and electrochemical impedance spectroscopy (EIS) measurements. Two coatings with different thicknesses, 55 and 115?μm, were investigated. The results showed that the corrosion rate of the thicker coating was lower than that of stainless steel by one order of magnitude. Local attack of the substrate was observed after the polarisation test of this coating, while the coating was still intact. The thinner coating and the stainless steel substrate showed similar corrosion rates. In this case, the substrate was severely attacked after the polarisation test. Two time constants were observed in the EIS spectra of both coatings which were related to charge transfer processes and pore resistance, respectively.