Electrochemical and analytical characterization of three corrosion inhibitors of steel in simulated concrete pore solutions

Corrosion inhibitors for steel,such as sodium phosphate (Na3PO4),sodium nitrite (NaNO2),and benzotriazole (BTA),in simulated concrete pore solutions (saturated Ca(OH)2) were investigated.Corrosion behaviors of steel in different solutions were studied by means of corrosion potential (Ecorr),linear polarization resistance (LPR),electrochemical impedance spectroscopy (EIS),and potentiodynamic polarization (PDP).A field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray analysis (EDXA) was used for observing the microstructures and morphology of corrosion products of steel.The results indicate that,compared with the commonly used nitrite-based inhibitors,Na3PO4 is not a good inhibitor,while BTA may be a potentially effective inhibitor to prevent steel from corrosion in simulated concrete pore solutions.     

Influence of oxides on high velocity arc sprayed Fe-Al/Cr_3C_2 composite coatings

1INTRODUCTION Arcspraying(AS)isatechniquethatthemet alisheatedtodropletsbyanelectricarcandthensprayedontosubstratesbythecompressedair. Highvelocityarcspraying(HVAS)technologyisdevelopedonthebasisofAS.Aspecialtubede signedaccordingtotheprincipleofaerodynamicsis mountedattheexitofcompressedair.Theveloci tyanddistributionofmelteddropletsbecomehigh erandmoreuniform,respectively.Asaresult,acoatingwithlowporosity(2%)andhighdensity andbondstrengthcanbeobtained[15].Fe Alin termetalliccompound…     

电弧喷涂涂层温度场及应力应变分析

为了分析电弧喷涂层的沉积过程，采用有限元分析软件ANSYS计算不同时刻以及不同位置涂层内的温度场、应力场，在建立传热模型过程中考虑了金属液滴向涂层的传热以及涂层向系统外的热量散失等问题.采用在厚度方向以微小层逐层叠加来模拟涂层的增厚，并以此为基础构造涂层有限元计算模型，应用单元生与死逐层激活层单元参与计算过程.实现移动边界以充分模拟真实的喷涂沉积过程，获得了涂层温度场、应力场的分布情况.并在此计算的基础上，分析了应力分布对涂层失稳的影响.     

加热扩散对电弧喷涂Al涂层的影响

为了提高Al涂层的抗高温氧化性及硬度,采用电弧喷涂方法在Q235碳钢基体上制备了Al涂层.结果表明,经过加热扩散处理后Al涂层和基体之间形成了扩散层.涂层厚度、加热温度与加热时间对扩散层具有一定影响.当加热温度为800℃和900℃时,Al涂层主要形成相为Fe Al、Fe Al2、Fe Al3和Fe2Al5.经过加热扩散处理后Al涂层具有优良的抗高温氧化性,且平均硬度相比未经加热扩散处理的Al涂层提高了10倍以上,利用扩散系数求出的扩散层深度与实际扩散层深度相近.     

电弧喷涂锡基巴氏合金层的磨损性能

针对电弧喷涂巴氏合金涂层组织的特殊性,研究在润滑条件下巴氏合金涂层的摩擦磨损性能,对该涂层的工程应用具有重要的参考价值.利用环块摩擦磨损试验分别对比了电弧喷涂、铸造以及堆焊方法制备的巴氏合金层与碳钢和铸铁构成摩擦副的磨损表现.借助于扫描电子显微镜、x 射线能谱以及x 射线衍射,分析了巴氏合金涂层的微观组织结构和磨损表面形貌,研究了其组织变化与耐磨性能之间的关系.实验结果表明：在润滑条件下,电弧喷涂巴氏合金涂层具有比铸造巴氏合金更好的减磨性能;选择合适的工艺参数可以制备组织致密、结合强度高,且具有很好磨损性能的巴氏合金涂层.     

Hot-corrosion mechanism of Ni-Cr coatings at 650°C under different simulated corrosion conditions

The oxidation and lower temperature hot corrosion (LTHC) processes occurring on the surface of Ni-Cr coatings produced by high velocity arc spray (HVAS) were studied. Several different conditions were studied under simulated boiler conditions at 650°C. The protection effect of an Al coating deposited by HVAS onto the Ni-Cr coating was also investigated. Microscope, X-ray diffraction and corrosion rate curves have been used to analyze corrosion mechanisms. The experimental results show that: 1) The oxidation rates are almost superposed in both air (no SO₃) and in simulated coal-fired gas (containing SO₃) as long as no salt was present on the surface. These rate curves show a logarithmic relationship. 2) When the surface is coated with salt (75%K₂SO₃ + 25%Na₂SO₃) the rate curve for LTHC of the Ni-Cr coated surface shows a parabolic shape in the simulated coal-fire flue gas. In air only the oxidation reaction takes place, the second type of LTHC was not seen. And 3) the Al over coating on the Ni-Cr enhances resistance to LTHC because an inter-metallic compound, Al₃Ni₂, forms at the Al/Ni-Cr interface and because of the increase in coating thickness.     

锅炉受热面NiCr涂层抗高温热腐蚀机制与性能的研究

针对电站锅炉受热面高温腐蚀的影响,通过采用电弧喷涂工艺,研究了Q235钢板表面电弧喷涂PS45、FeCrAl、4Cr13合金涂层后在高温条件下的热腐蚀机制与性能.热腐蚀动力学试验和分析结果显示,在700℃下腐蚀77 h、Na2SO4＋K2SO4盐膜量为3-4 mg/cm2的试验条件下,测试得到的PS45、FeCrAl、4Cr13合金涂层的热腐蚀速度分别为υ=0.38t-0.59、υ=1.35t-0.12和υ=1.79t-0.23.涂层表面的成分和组织分析结果表明,Q235钢板表面的PS45涂层之所以表现出比FeCrAl、4Cr13涂层更高的抗热腐蚀（Na2SO4/K2SO4）性能,其原因在于PS45镍基合金中含有最多的Cr,涂层表面的Cr2O3膜层具有较高的连续性、致密性和稳定性.     

锅炉受热面NiCr涂层抗高温热腐蚀机制与性能的研究

针对电站锅炉受热面高温腐蚀的影响,通过采用电弧喷涂工艺,研究了Q235钢板表面电弧喷涂PS45、FeCrAl、4Cr13合金涂层后在高温条件下的热腐蚀机制与性能.热腐蚀动力学试验和分析结果显示,在700℃下腐蚀77 h、Na2SO4+K2SO4盐膜量为3~4 mg/cm2的试验条件下,测试得到的PS45、FeCrAl、4Cr13合金涂层的热腐蚀速度分别为υ=0.38t-0.59、υ=1.35t-0.12和υ=1.79t-0.23.涂层表面的成分和组织分析结果表明,Q235钢板表面的PS45涂层之所以表现出比FeCrAl、4Cr13涂层更高的抗热腐蚀(Na2SO4/K2SO4)性能,其原因在于PS45镍基合金中含有最多的Cr,涂层表面的Cr2O3膜层具有较高的连续性、致密性和稳定性.     

X100钢在伊盟土壤模拟溶液中腐蚀行为的研究

通过自腐蚀电位（Ecorr）、交流阻抗谱等电化学方法,研究了X100钢在内蒙古伊克昭盟土壤模拟溶液中的腐蚀行为.实验结果表明,在实验初期,X100钢自腐蚀电位急剧下降,腐蚀初期腐蚀介质充足,吸氧腐蚀较为充分,腐蚀速率较快.但随着试验时间的增加,X100钢的自腐蚀电位逐渐近于平缓;而在整个实验周期中X100钢发生了非均匀的腐蚀现象.XRD测试分析表明,X100钢的腐蚀产物主要为FeOOH,Fe2 O3和Fe3O4.     

High temperature behaviors of high velocity arc sprayed Fe-Al/Cr3C2 composite coatings

Fe-Al/Cr3C2 composite coatings were manufactured using high velocity arc spraying （HVAS） technology. The high temperature erosion, wear and corrosion resistance of the coatings were investigated. The coating properties such as bonding strength, porosity, hardness as well as microstructures were characterized. The results show that the coatings have relatively high heat tremble bond strength, hardness, and typical layer-shaped coatings＇ microstructures. With the rise of temperature, the coating erosion resistance increases too; the impingement angel does effects on erosion properties, and the erosion mechanism changes from ductile to brittle behaviors at 450℃. The coatings have good room temperature wear resistance and relatively good high temperature resistance. The wear mechanism of the coatings is peeling wear behavior. The coatings have excellent high temperature corrosion resistance because of the produce of oxides during corrosion.     

Electrochemical corrosion behavior of carbon steel with bulk coating holidays

With epoxy coal tar as the coating material, the electrochemical corrosion behavior of Q235 with different kinds of bulk coating holidays has been investigated with EIS （Electrochemical Impedance Spectroscopy） in a 3.5vo1% NaCI aqueous solution. The area ratio of bulk coating holiday to total coating area of steel is 4.91%. The experimental results showed that at free corrosion potential, the corrosion of carbon steel with disbonded coating holiday is heavier than that with broken holiday and disbonded ＆ broken holiday with time; Moreover, the effectiveness of Cathodic Protection （CP） of carbon steel with broken holiday is better than that with disbonded holiday and disbonded ＆ broken holiday on CP potential -850 mV （vs CSE）. Further analysis indicated that the two main reasons for corrosion are electrolyte solution slowly penetrating the coating, and crevice corrosion at steel/coating interface near holidays. The ratio of impedance amplitude （Z） of different frequency to minimum frequency is defined as K value. The change rate of K with frequency is related to the type of coating holiday.     

Electrochemical behavior of different shelled microcapsule composite copper coatings

Copper/liquid microcapsule composite coatings with polyvinyl alcohol (PVA), gelatin or methyl cellulose (MC) as shell materials were prepared by electrodeposition. The influence of shell materials on the corrosion resistance of the composite coatings in 0.1 M H2SO4 was investigated by means of electrochemical techniques, scanning electron microscopy (SEM), and energy dispersion spectrometry (EDS). The results show that the participation of microcapsules can enhance the corrosion resistance of the composite ...     

Effect of nano-SiC particles on the corrosion resistance of NiP-SiC composite coatings

NiP-SiC (≈11wt% P) composite coatings were electroplated in a Brenner type plating bath. The coatings had amorphous nano-phase composite structure. Direct current and alternating current electrochemical tests were carried out on such coatings in a 3.5wt% solution of NaCl to evaluate their corrosion resistance. The potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) tests, and exposure experiments all show that the corrosion resistance of NiP-SiC coatings first increases and then decre...     

中性盐雾腐蚀钢板的滞回性能试验

为研究中性盐雾环境下不同腐蚀程度钢板的滞回性能变化规律,通过人工喷洒盐雾加速腐蚀方法,获得了不同腐蚀程度下钢板试件;然后对每组试件进行循环加载试验并得到滞回曲线,分析其滞回性能;同时采用Ramberg-Osgood模型拟合钢材的循环骨架曲线,并分析其系数变化规律;最后基于首次加载准则,卸载准则,循环骨架准则,再加载曲线准则等建立了钢材滞回本构模型.试验结果表明:在循环荷载作用下,钢材出现循环硬化、峰值点指向效应等现象;应用Ramberg-Osgood模型拟合效果较好;随着腐蚀程度增加,钢材各力学性能指标均出现下降,延性劣化加重,且钢材循环强化系数呈现减小的趋势,而循环强化指数变化规律不明显;模型与试验结果吻合较好.     

Erosion-Corrosion Behaviors of High Velocity Arc Sprayed Fe-Al/Cr3 C2 Coating

1 IntroductionArc Spraying (AS) is a technique that utilizes anelectric arc as the heat source to melt wires into droplets ,which are subsequentlysprayed ontosubstrates bytheflowof compressed air . High Velocity Arc Spraying (HVAS)technology was developed on the basis of AS. Aspecialtube designed according to the principle of aerodynamicswas mounted at the exit of compressed air .Thenthe hightemperature fuel air or compressed air was accelerated bythe tube .Hence ,a higher velocityand be…     

机械合金化Ni-20Cr-2.5Al合金的电化学腐蚀研究

利用电化学方法,结合XRD、TEM等表面分析技术,研究了机械合金化Ni-20Cr-2．5Al及粗晶Ni- 20Cr-2．5Al合金在3．5％NaCl溶液中的腐蚀性能．结果表明粗晶Ni-20Cr-2．5Al合金在3．5％NaCl溶液中的电化学性能要好于机械合金化方法制备的Ni-20Cr-2．5Al合金．     

HVOF喷涂Co基WC涂层的耐锌腐蚀行为

为了提高热镀锌用辊件的耐腐蚀性,试验采用超音速火焰喷涂方法制备WC-12Co涂层,研究了涂层在450 ℃锌液中的耐腐蚀性能以及失效机制.将316L/WC-12Co涂层进行液锌腐蚀,以扫描电镜能谱分析、x-射线衍射方式分析对比了未经过腐蚀试件、腐蚀5天试件、腐蚀10天试件的组织变化和相组成,结果显示涂层基体Co受液锌腐蚀生成Co与Zn化合物,引发横向裂纹,导致涂层剥落.涂层全部剥落后保护失效,使母材被液锌直接严重腐蚀,最终生成锌渣FeZn₁₃.     

Effects of electroplated coatings on corrosion behavior of Ti-1023/30CrMnSiA galvanic couple

Galvanic corrosion behavior of Ti-1023 titanium alloy coupled 30CrMnSiA steel was investigated in 3.5% NaCl solution. Particular attention was given to the effect of three different electroplated coatings on corrosion behavior of the galvanic couple. Galvanic corrosion test was conducted on Ti-1023 titanium alloy which coupled Ni-electroplated 30CrMnSiA, Zn-electroplated 30CrMnSiA, Cd-electroplated 30CrMnSiA and bare 30CrMnSiA, respectively. Corrosion properties including open circuit potential （Eoc）, galvanic corrosion potential （Eg）, and galvanic corrosion current （lg） were monitored. Corrosion morphology was observed by optical microscope （OM） and corrosion mechanism was analyzed and discussed. The results show that the three electroplated coatings improve the corrosion resistance of the anode in different magnitudes. Ni-electroplated 30CrMnSiA and Cd-electroplated 30CrMnSiA coatings are found to be least susceptible to galvanic corrosion when coupled Ti-1023 titanium alloy. Zn-electroplated 30CrMnSiA is moderately susceptible to galvanic corrosion. But the bare 30CrMnSiA is highly susceptible to galvanic corrosion in corrosive environment.     

Influence of oxides on high velocity arc sprayed Fe-Al／Cr3C2 composite coatings

Fe-Al/Cr3C2 coatings were sprayed on low steel by high velocity arc spraying(HVAS) technology. The influences of oxides on erosion, corrosion and wear behavior for high velocity arc sprayed Fe-Al/Cr3C2 coatings were studied. The results show that HVAS-sprayed Fe-Al/Cr3C2 coatings have good erosion, heat corrosion and wear resistance. The erosion resistance improves with the increase of the temperature. On one hand, the ferrous oxides are incompact, so they peel off the surface of the coatings easily during the high temperature erosion. On the other hand, compact Al2O3 films on the surface can protect the coatings.     

工业纯铝在模拟海水中的电化学腐蚀行为

为研究铝在海水中的腐蚀过程,采用电化学阻抗谱、浸泡试验、扫描电子显微镜研究工业纯铝在模拟海水中的腐蚀行为.结果表明:铝在模拟海水中发生点蚀的区域为富含Fe的晶间化合物处,点蚀半径随时间的增加而扩大.铝在模拟海水中的溶解曲线分为4个区间:活性溶解区、过渡区、过钝化区、钝化区.铝在模拟海水中,极化电位为过钝化区时,转移电阻R t随着电位的升高而变小,铝发生严重的点蚀;而极化电位为钝化区时,铝的转移电阻R t随着电位的升高基本不变,铝的溶解行为受到抑制.工业纯铝在模拟海水中发生点蚀的电位区间是-0.45～-0.65 V,钝化电位区间为-0.75～-0.85 V.