Q235钢表面铈盐掺杂乙烯基三乙氧基硅烷膜制备及耐蚀性能

在Q235钢表面制备铈盐掺杂乙烯基三乙氧基硅烷膜。利用电化学阻抗谱(EIS)确定了最佳铈盐添加量,利用EIS和动电位极化法研究了涂覆掺杂硅烷膜的Q235钢在3.5% NaCl水溶液中的耐蚀性能,利用扫描电镜(SEM)观察了掺杂硅烷膜的表面形貌。结果表明,铈盐最佳添加量为1×10^-3 mol/L,经涂镀掺杂硅烷的Q235钢在腐蚀过程中的阳极反应和阴极反应受到抑制,与空白Q235钢相比其腐蚀电流密度减小近3个数量级,极化电阻提高3个数量级,低频阻抗值提高至少4个数量级。     

镀锌钢板表面硅烷膜的制备及性能研究

目的提高镀锌钢板的耐腐蚀性能。方法在镀锌钢表面制备双-[γ-(三乙氧基硅)丙基]四硫化物(BTESPT)和乙烯基三乙氧基硅烷(VTES)单一硅烷膜和双硅烷膜,并掺杂缓蚀剂和稀土盐改性制备复合膜,用动电位极化曲线测试研究各种硅烷膜在3.5%Na Cl溶液中对镀锌钢的腐蚀防护性能。结果 VTES硅烷膜的最佳工艺条件为:V(VTES):V(乙醇):V(水)=7:30:70,p H=4.5,水解2 d,成膜时间20 min,固化温度100℃,固化时间30 min,VTES硅烷膜耐蚀性比BTESPT硅烷膜略差,但更经济。双层硅烷膜能够提高物理屏障作用,可以进一步增加耐蚀性。当铈盐和硅烷混合水解再成膜时,硅烷膜的耐蚀性最好。在硅烷水解溶液中加入0.01 mol/L的吡咯,可以制得耐蚀性优良的缓蚀剂掺杂硅烷摸。结论铈盐和吡咯改性硅烷膜对镀锌钢具有良好的保护作用。     

镀锌钢表面硅烷膜的耐蚀性能研究

采用浸涂技术,在热镀锌（HDG）钢板表面制备3-氨丙基甲基二乙氧基硅烷膜。通过电化学方法研究硅烷膜在3．50％的氯化钠溶液中的耐蚀性能,并用SEM研究存在硅烷膜的镀锌钢在腐蚀前后的形貌变化。结果表明,形成硅烷膜的镀锌钢在3．50％的氯化钠溶液中的自腐蚀电流密度下降到2．434×10^-8A·cm^-1自腐蚀电位正移。经SEM测试表明,硅烷膜在腐蚀前后的形貌几乎不变,耐蚀性能明显优于空白样镀锌钢。     

溶胶-凝胶法制备AA5052系铝合金耐蚀性保护膜

采用乙烯基三乙氧基硅烷(VS)和正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶法在AA5052铝合金表面制备了倍半硅氧烷(SSO)杂化膜。采用动电位极化法和电化学阻抗法测试了膜层的耐腐蚀性能,并考察了正硅酸乙酯的含量对其膜层的影响。结果表明,杂化膜能有效抑制AA5052铝合金的腐蚀反应,且当正硅酸乙酯的含量为20%时,杂化膜涂层的耐腐蚀性最好。     

硅烷膜的阴极电化学辅助沉积及其防护性能

采用电化学辅助技术在LY12铝合金表面沉积了两种防护性硅烷膜（1，2-二-（三乙氧基硅基）乙烷（BTSE）膜与十二烷基三甲氧基硅烷（DTMS）膜），电化学阻抗谱测试结果显示，经硅烷化处理后铝合金的耐蚀性能得到大幅度提高，并且发现在阴极电位下沉积所得硅烷膜的耐蚀性能较常规“浸涂法”有明显提高；两种硅烷膜均存在一个最佳的“临界阴极电位”（-0．8V），在此电位下制得的膜耐蚀性最佳，扫描电镜观察显示临界电位下所得硅烷膜最为完整致密，电位过正不利于成膜，而电位继续变负膜表面呈现多孔形貌，可能与氢气的生成并溢出破坏表面有关．由于在硅烷分子中含有疏水性较强的十二烷基长链，DTMS膜具有更好的耐蚀性．     

双一[γ一（三乙氧基硅）丙基]四硫化物处理热镀铝锌层的耐蚀性研究

采用双-[γ-(三乙氧基硅)丙基]四硫化物(BTESPT)硅烷钝化液对热镀铝锌钢板进行了钝化处理.研究了在5%NaCl溶液中未钝化、硅烷钝化及铬酸盐钝化热镀铝锌钢板的极化曲线和电化学交流阻抗谱.通过中性盐雾试验比较了硅烷钝化膜与铬酸盐钝化膜的耐蚀性能.结果表明:经硅烷钝化液钝化后的热镀铝锌钢板,其腐蚀电位和电流密度下降,极化电阻增大,硅烷钝化膜抑制了热镀铝锌钢板的腐蚀过程,使得耐蚀性能远远高于铬酸盐钝化后的热镀铝锌钢板.     

镀锌钢板表面稀土镧盐、硅烷协同钝化研究

    提出了镀锌钢板的稀土镧盐、硅烷协同钝化工艺,先在镀锌钢板表面沉积一层稀土镧盐转化膜,再用乙烯基三(β-甲氧基乙氧基)硅烷处理得到复合膜.盐雾试验、醋酸铅点滴试验、失重实验和电化学交流阻抗谱(EIS)测定表明,复合膜的耐蚀性优于单一镧盐转化膜和常规铬酸盐转化膜.扫描电镜（SEM）结果表明,复合膜表面极其致密均匀平整.漆膜划格试验结果表明,复合膜附着力达到5B标准,再涂装性可靠.     

AA6061-T6铝合金表面纳米Y_2O_3改性硅烷膜的耐蚀性

采用动电位极化曲线,电化学阻抗谱(EIS)和中性盐雾试验(NSS)研究了溶液中加入不同含量纳米Y2O3对铝合金AA6061-T6表面硅烷膜耐蚀性的影响,采用扫描电镜(SEM)对其形貌进行了观察。结果表明,在1,2-双-三乙氧基硅烷(BTSE)溶液中加入少量纳米Y2O3可提高硅烷膜在3.5%NaCl溶液中的耐蚀性。硅烷膜对铝合金的保护只起到物理屏障作用。纳米Y2O3抑制了电化学腐蚀过程中阴极还原反应的发生,但不影响电极反应的动力特征。SEM表明在BTSE硅烷溶液中添加10~20mg/L的纳米Y2O3后,硅烷膜表面变得平滑致密。     

热镀锌钢表面硅烷膜的腐蚀电化学性能

将热镀锌钢板在7 %(体积比)、pH＝4的乙烯基三甲氧基硅烷溶液中40 ℃下处理2 min,获得了硅烷膜试样.应用极化曲线和电化学交流阻抗谱(EIS)评价了硅烷膜在5 % NaCl溶液中的耐蚀性能,采用俄歇电子能谱(AES)分析了膜层的成分和结构特性.结果表明,硅烷膜主要由C、O、Si等元素组成,硅烷分子并非是简单地以物理吸附的方式存在于热镀锌层上,而是通过Si-O-Zn键使得硅烷界面层与热镀锌层紧密结合在一起.硅烷膜能同时抑制Zn腐蚀过程中的阳极和阴极反应,其极化阻抗值Rp可达5.53 kΩ·cm2.硅烷膜的低频与高频容抗弧几乎合成一个弧,表明腐蚀过程中硅烷膜层已经很致密,界面电容很大,Cl﹣难以通过膜层间隙到达Zn基体表面.     

铝合金表面不同硅烷化预处理的耐蚀性研究

采用浸涂工艺,用pH=4～5,体积分数＜3%的3种硅溶胶即γ-缩水甘油醚丙基三甲氧基硅烷（GPTMS）、双-（三乙氧基硅）乙烷（BTSE）和双-[γ-（三乙氧基硅）丙基]四硫化物（BTSPS）对YL12铝合金表面进行处理,GPTMS和双硅烷膜层分别采用100℃×60min和130℃×60min工艺固化,并用动电位（PDS）和电化学阻抗谱（EIS）测试了不同硅烷化膜层在3.5mass% NaCl溶液中的耐蚀性并与铬酸盐处理的耐蚀性进行了比较.结果表明,双功能硅烷化膜层的耐蚀性优于功能性硅烷化膜层的耐蚀性,BTSPS硅烷化膜层的耐蚀性最优.     

GD‐OES and electrochemical study of Ce containing conversion layers of hot dip galvanised and by Sendzimir process continuously hot dip galvanised steel plates

The present work is focused on the conversion layers of hot dip galvanised and continuously hot dip galvanised steel sheets produced by ISD DUNAFERR, Co., Ltd. The conversion coatings on the galvanised steel plates were produced by dipping the plates into solutions of rare earth salts for different immersion periods. The applied rare earth salts were, cerium nitrate and cerium chloride, respectively. The corrosion resistance of the treated plates was tested by DC polarisation measurements and electrochemical impedance spectroscopic method (EIS). The most promising conversion layers were subjected to special corrosion test modelling the effect of the squeezing of plates or coils during storage and delivering and the humidity, simultaneously. The qualitative properties of the corroded surface were tested by glow discharge optical emission spectroscopy (GD‐OES).     

Korrosionsbeständigkeit metallisch und organisch vorveredelter Stahlfeinbleche in der Freibewitterung

Corrosion resistance of unpainted and coil-coated sheets under atmospheric exposure An extensive study was carried out to compare the corrosion behaviour of unpainted and coil-coated hot dip galvanised and Galfan-coated sheets under atmospheric exposure. FIat and roll-formed test pieces with various metallic and organic coatings were exposed to atmospheric weathering at five different locations for 9 years. The corrosion behaviour of unpainted specimens was determined quantitatively by measuring the loss of metallic coating thickness and by visual assessment of red rust on surfaces and bends. In the case of organically coated specimens formation of red rust and blistering on surfaces and bends was assessed visually and creepage at scores and cut edges was measured. The results show that Galfan coatings are subject to much slower weathering than hot dip galvanised coatings. It is concluded that in most applications users could select the next lower coating thickness group when using Galfan instead of hot dip galvanised sheet. Visual assessment of corrosion damage (red rust, blisters, creepage) also leads to the overall conclusion that both unpainted and coil coated Galfan perform much better than hot dip galvanised sheet in natural weathering. The advantages of using Galfan especially for building applications are thus being established.     

The corrosion resistance of hot dip galvanised steel and AA2024-T3 pre-treated with bis-[triethoxysilylpropyl] tetrasulfide solutions doped with Ce(NO3)3

The present work aims at evaluating the anti-corrosion behaviour of a novel pre-treatment based on bis-[triethoxysilylpropyl] tetrasulfide (BTESPT) doped with cerium nitrate for application on hot dip galvanised steel and AA2024-T3 substrates. The corrosion resistance was evaluated by electrochemical impedance spectroscopy (EIS) and by the scanning vibrating electrode technique (SVET), during immersion in NaCl solutions. The electrochemical results showed that the pre-treatment provides excellent corrosion protection to the substrates. Furthermore, the results evidenced improved protection comparatively to the use of undoped BTESPT pre-treatments, both for galvanised steel and AA2024-T3. This improvement is most likely due to enhanced barrier properties of the film and additional active corrosion protection originated from the inhibiting action of the cerium-based inhibitor impregnated in the silane matrix.     

Zinc runoff from galvanised steel materials exposed in industrial/marine environment

Abstract

An investigation has been carried out to assess the zinc runoff from a variety of galvanised materials over 16 months at the industrial/marine Port Talbot weathering site. Over 16 months of exposure, bare zinc, and Electrozinc have the highest levels of zinc runoff (4·38 and 4·20 g m^-2) followed by general galvanised steel substrates, i.e. hot dip galvanised (HDG) steel (0·15 wt-%Al) (2·87 g m^-2) and iron zinc intermetallic galvanised steel (galvanneal, 2·36 g m^-2). Galvanneal (IZ) has a higher initial runoff rate than HDG due to the presence of iron/zinc intermetallic in the coating that promotes anodic zinc dissolution. The HDG has a more constant runoff rate that exceeds IZ after 7-8 months due to build up of corrosion products on the IZ surface. Aluminium/zinc alloy coated steels have a much lower runoff rate than general galvanised materials as the aluminium present in the structure provides a strongly protective oxide barrier coating improving corrosion resistance (Galfan 5 wt-%Al, 2·04 g m^-2, and Z alutite 55 wt-%Al, 0·67 g m^-2). Organically coated steels show relatively little zinc runoff (< 0·25 g m^-2) indicating their effectiveness in preventing surface corrosion. Runoff levels measured do not exceed permissible levels of zinc for drinking water and the measured zinc runoff levels pose little threat to organisms if leached into soil. Using an accelerated laboratory test in which distilled water is sprayed onto specimen panels in a recirculatory system for 100 h a good correlation can be obtained with external exposure for up to 6 months exposure. For 12 months exposure iron zinc intermetallic galvanising (galvanneal) begins to become covered in a protective oxide layer, which cannot form under the conditions of the accelerated test. Despite this, the fit for most specimen types is excellent. Where the predictive test fails is when the galvanising layer is breached revealing an efficient iron cathode site. This occurs first for electrocoated zinc after 16 months exposure. Similar predictive results can be obtained using a scanning vibrating electrode technique (SVET) in a semiquantitative manner and an immersion electrolyte of 0·1 wt-%NaCl. Again the predictions are initially very accurate but following 12 months exposure the fit for specimens of electrozinc is poor due to the breaching of the galvanising layer.     

Mechanistic changes in cut-edge corrosion induced by variation of organic coating porosity

The scanning vibrating electrode technique (SVET) has been used to investigate the mechanism of corrosion occurring at exposed metallic cut edges of galvanised steel materials coated with identical thickness organic polymeric layers. Organically coated galvanised steel samples have been prepared by application of a 30 μm polyester coating to both sides of a pre-treated hot dip zinc (99.85%) aluminium (0.15%) galvanised steel substrate. In separate samples the coatings were applied to both sides simultaneously and then cured or applied sequentially to each side curing after each application. Electrical impedance spectroscopy (EIS) was used to probe the porosity of the resulting organic coatings. This revealed that simultaneous coating application and curing resulted in both polymer layers showing EIS pore resistance of 0.6 MΩ whereas sequential coating resulted in one side showing a pore resistance of 0.6 MΩ and the other showing a capacitive EIS response with no measurable porosity. When the metallic cut edges of organically coated steel materials, coated with symmetric thicknesses of organic layers of identical pore resistance, are exposed to 5% NaCl the SVET iso-current contour maps show that both zinc layers behaving as local anodes. In addition, there is significant sample passivation in the 24 h exposure period. In the samples coated with materials of identical thicknesses but different porosity, the SVET iso-current contour maps show anodic activity focussed beneath the organic coating with the capacitive EIS signature. The greater porosity of the coating on the opposite side of the exposed cut edge enables oxygen transport to the delaminating surface and this forces anodic activity onto the other zinc layer.     

In situ infrared reflection spectroscopy studies of the initial atmospheric corrosion of Zn–Al–Mg coated steel

NaCl induced atmospheric corrosion of ZnAl2Mg2 coated, electrogalvanised (EG) and hot dipped galvanised (HDG) steel was studied using in situ infrared reflection absorption spectroscopy, XRD and SEM. Initial corrosion leads to the formation of Mg/Al and Zn/Al layered double hydroxides (LDHs) on ZnAl2Mg2, due to the anodic dissolution of Zn–MgZn2 phases and cathodic oxygen reduction on Zn–Al–MgZn2, Al-phases and on zinc dendrites. In contrast to EG and HDG, were no ZnO and Zn₅(OH)₈Cl₂⋅H₂O detected. This is explained by the buffering effect of Mg and Al which inhibit the ZnO formation, reduce the cathodic reaction and corrosion rate on ZnAl2Mg2.     

Electrochemical impedance spectroscopy study on multi-layered coated steel sheets

Electroplating technique is used to coat nickel over the coated substrates like galvannealed and galvanized, and uncoated substrate of cold rolled closed annealed steel sheets as well. These coated substrates are exposed to 3.5% aqueous NaCl solution in a flat cell to carry out the corrosion tests. The effect of nickel coating on galvannealed, galvanized and cold rolled closed annealing steel sheets is studied for their anti-corrosive performance by electrochemical impedance spectroscopy. Electrochemical impedance data were analysed by using Bode and Nyquist plot by considering the metal-coating-electrolyte interface as an electrical equivalent circuit model. The circuit elements i.e. polarisation resistance and coating capacitance are determined to evaluate the corrosion behaviour of these multilayered coatings. The changes in the impedance characteristics of the systems are found to occur as a function of exposure time in all the three cases. These results have showed differences in the protective characteristics of the three systems, where the nickel coated galvannealed exhibited superior corrosion resistance compared to nickel coated cold rolled closed annealed and galvanised.     

Influence of steel gauge on the microstructure and corrosion performance of zinc alloy coated steels

Zn-4.8 wt% Al coated steels exhibited a polynomial increase in Zn loss from the cut edge with increasing steel gauge for weight loss and SVET Zn loss in 0.1% NaCl in contrast to a linear increase observed for hot dipped galvanised (HDG) steels. Increasing steel gauge decreased nucleation and increased growth of Zn dendrites for Zn-4.8 wt% Al coated steels. SVET data showed larger Zn dendrites associated with thicker gauges produced more damaging anodes than small dendrites on thinner samples. A polynomial relationship was observed between dendrite size and Zn loss suggesting that microstructure influenced Zn loss in unison with the increased cathodic activity on thicker steels.