Electrochemical corrosion behavior of micrometer-sized porous Ti3SiC2 compounds in NaCl solution

The electrochemical corrosion behavior of reactively synthesized porous Ti₃SiC ₂ in 1 M NaCl solution was investigated compared with that of porous TiAl. Porous Ti ₃SiC ₂ and TiAl have high-purity single phase characteristics with open porosities of 48% and 41% and maximum apertures of 6.9 and 16.3 µm, respectively, which show positive direction shift behavior of open circuit potential at the early immersion stage with stable potential ranges of 0.25~0.27 and −0.36~−0.38 V (vs. saturated calomel), respectively. The electrochemical corrosion procedures of the two porous compounds exhibit three-stage characteristics of activation, passivation, and breakdown. Porous Ti ₃SiC ₂ has a much larger ohmic resistance and Warburg coefficient than TiAl. The passivation films of the two porous compounds consist of an inner layer with a larger resistance and a porous outer layer. Porous Ti ₃SiC ₂ has a significantly larger resistance and relatively smaller capacitance for the inner passivation film, indicating better corrosion resistance stability.     

超音速火焰喷涂Cr_3C_2-NiCr涂层在3.5%NaCl溶液中的腐蚀性能及机理

采用超音速火焰喷涂(high velocity oxy-fuel,HVOF)技术在Q235钢基体上制备了Cr3C2-Ni Cr涂层,借助X射线衍射(XRD)和扫描电镜(SEM)等方法分析了涂层的相组成和微观组织,研究涂层与镀铬层在质量分数为3.5%Na Cl溶液中的腐蚀性能.结果表明,涂层主要由Cr3C2,Cr7C3和Ni Cr等相组成,涂层的致密度高,层状结构明显,含少量孔隙.阻抗谱曲线表明,Cr3C2-Ni Cr涂层对基体的保护作用良好,在Na Cl溶液中浸泡时间40 d后,极化电阻为2.8 kΩ,而镀铬层失效严重,极化电阻为300Ω.极化曲线表明,Cr3C2-Ni Cr涂层在浸泡周期内腐蚀电位平稳,腐蚀电流缓慢增加.镀铬层的腐蚀电位下降较快,腐蚀速率成倍增加.孔洞是影响Cr3C2-Ni Cr涂层耐蚀性的重要原因,影响镀铬层耐蚀性的主要原因是裂纹.     

烧结钕铁硼磁体表面CeO2/硅烷复合涂层的制备及其耐蚀性能

采用浸涂方式在烧结钕铁硼磁体表面制备CeO2/硅烷复合涂层,研究了硅烷水溶液中纳米CeO2颗粒掺杂量对复合涂层性能的影响,通过扫描电镜、能谱分析仪、动电位极化曲线及中性盐雾试验对所制备的CeO2/硅烷复合涂层的形貌、元素分布以及耐腐蚀性能进行分析。结果表明:纳米CeO2颗粒的添加增强了涂层的硬度,提高了硅烷涂层的屏蔽性能,延长了腐蚀溶液渗入硅烷涂层的腐蚀通道,复合涂层耐中性盐雾试验能力可达24 h。但由于纳米颗粒只是机械的镶嵌到复合涂层中,不会改变硅烷涂层在固化过程中醇基之间脱水缩合反应的本质,在NaCl溶液中,复合涂层依然会形成高低不同的交联密度区,CeO2/硅烷复合涂层失效的主要原因依然是在交联密度低的区域首先水解溶解导致的。     

SiC颗粒尺寸对镍基复合镀层耐磨性和耐蚀性的影响

在正交实验基础上,对比研究微米SiC(平均粒径1.5 μm)和纳米SiC(平均粒径20 nm)增强复合镍基镀层的摩擦磨损行为和耐腐蚀性能.通过TEM、SEM、EDX和XRD等手段研究颗粒分散状态以及复合镀层的表面和截面形貌、成分及相结构.采用球-盘滑动摩擦磨损试验机研究复合镀层的耐磨性.电化学阻抗谱测量在3.5%的NaCl水溶液中进行.结果表明:微米级颗粒增强复合镀层可以获得更高的表面硬度,两种增强复合镀层具有相似的摩擦磨损行为.电化学阻抗谱分析表明:SiC颗粒的加入可以提高镀层的耐腐蚀性,且纳米颗粒复合镀层具有更好的耐蚀性.     

Water soluble conducting polymer composite of polyvinyl alcohol and leucine: An effective acid corrosion inhibitor for mild steel

A new corrosion inhibitor namely poly(vinyl alcohol‐leucine) composite (PVAL) has been synthesized and its influence on corrosion inhibition of mild steel in 1 M hydrochloric acid solution has been studied by weight loss and potentiodynamic polarization techniques. The composite (PVAL) showed more than 95% inhibition efficiency (IE) at an optimum concentration of 0.6% by weight. The inhibition efficiency of inhibitor has been found to vary with inhibitor concentration, solution temperature, and immersion time. Various kinetic and thermodynamic parameters (E_a, ΔH_o, ΔS_o for corrosion and ΔG_ads, ΔH_ads, ΔS_ads for adsorption) reveal a strong interaction between inhibitor and mild steel surface. The negative values of ΔG_ads indicate the spontaneous adsorption of the inhibitor on mild steel surface. Potentiodynamic polarization studies showed PVAL as mixed type inhibitor. It inhibits mild steel corrosion by blocking the active sites of the metal. Electrochemical impedance spectroscopic (EIS) techniques were also used to investigate the mechanism of corrosion inhibition.     

镍磷非晶纳米晶复合镀层的制备及其耐蚀性

对电沉积12．3％P（质量分数）镍磷合金进行热处理，部分晶化获得非晶纳米晶复合镀层。利用X射线衍射仪、透射电镜和高分辨透射电镜分析镀层的结构。结果表明，镀态时镀层呈典型的非晶态结构，控制热处理工艺可得到非晶纳米晶的复合镀层。通过动电位极化曲线（3．5％NaCI溶液）测定，得知部分晶化的镀层耐蚀性得到改善。由于具有少量纳米晶相镶嵌于连续非晶相上，非晶纳米晶复合结构的镍磷合金镀层耐蚀性优于非晶态镍磷合金镀层。     

Pitting corrosion of Al2024-T3 in sodium chloride solution

1　ＩＮＴＲＯＤＵＣＴＩＯＮＡｌｕｍｉｎｕｍａｎｄｉｔｓａｌｌｏｙｓａｒｅｗｉｄｅｌｙｕｓｅｄｉｎｔｈｅｔｅｌｅｃｏｍｍｕｎｉｃａｔｉｏｎｓ,ｅｌｅｃｔｒｏｎｉｃｓａｎｄａｖｉａｔｉｏｎｉｎｄｕｓ ｔｒｉｅｓｂｅｃａｕｓｅｏｆｔｈｅｉｒｇｏｏｄｅｌｅｃｔｒｉｃａｌｃｏｎｄｕｃｔｉｖｉｔｙａｎｄｐｒｏｃｅｓｓａｂｉｌｉｔｙ .Ｂｕｔｔｈｅｙａｒｅｖｅｒｙｓｕｓｃｅｐｔｉｂｌｅｔｏｐｉｔｔｉｎｇｃｏｒｒｏｓｉｏｎｉｎａｑｕｅｏｕｓｅｎｖｉｒｏｎｍｅｎｔｓ ,ａｎｄｔｈｅ ｐｉｔｔｉｎｇｃｏｒｒｏｓｉｏｎ ｐ…     

Electrochemical corrosion behavior of arc sprayed Zn-Al coatings

Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coatings were studied with potentiodynamic measurement in 5 % NaCl solution. Compared with pure Zn, pure Al and Zn-15Al coatings, Zn-26Al coatings show a higher corrosion resistance in salt solution. The potentiodynamic polarization tests show that the corrosion resistance of Zn-Al coatings increases as Al content is raised. Pure Al coating exhibits different electrochemical behaviors with other coatings. The corrosion initiated at the micro-pores of the coating and the underlying corrosion mechanism is very similar to that of the pitting corrosion.     

Al_2O_3含量对Al_2O_3-Al复合涂层组织和摩擦磨损性能的影响

通过改变喷涂粉末中Al2O3和Al的比例,在AZ91D镁合金表面制备不同Al2O3含量的等离子喷涂Al2O3-Al复合涂层。对复合涂层的显微组织、硬度和摩擦磨损性能进行表征,研究Al2O3含量对涂层组织和磨损性能的影响。结果表明,涂层组织为带状Al2O3分布在致密的Al基体上,Al2O3内可见细微的片层结构,且层与层间存在一定的孔隙。复合涂层中Al平均硬度62HV,Al2O3平均硬度达1380 HV。摩擦磨损实验证实,复合涂层具有较小的摩擦系数和较低磨损量,大大改善了镁合金表面的抗磨损性能。涂层中Al2O3体积少于Al时,Al2O3增加使涂层的抗磨效果增强。涂层中Al2O3体积超过Al后,涂层的孔隙增多、涂层变脆,其耐磨损性能下降。     

Cu/Ti在模拟海水中的电偶腐蚀行为(英文)

采用电化学阻抗谱、电化学噪声和扫描电镜等技术研究了纯铜、铜/钛耦合电极在模拟海水中的腐蚀行为。结果表明:纯铜的腐蚀过程分2个阶段,其腐蚀阻抗和点蚀参数SE均遵循先增后降的规律,而其腐蚀参数SG的变化规律则正好相反;铜/钛耦合电极的腐蚀过程则由3个阶段组成,其腐蚀阻抗和点蚀参数SE均遵循先降后升到最后再降的规律,而其腐蚀参数SG则同样反向变化。铜和钛之间的电势差加速了纯铜的点蚀萌生,同时铜/钛耦合电极的腐蚀电位总是正于纯铜的腐蚀电位。     

纳米结构Ni-TiN复合薄膜的电沉积及腐蚀行为

采用电沉积方法在黄铜基底上制备纳米结构的Ni-TiN复合薄膜。用扫描电镜（SEM）及透射电镜（TEM）对其微观结构进行表征,利用X射线衍射（XRD）分析其平均晶粒尺寸,采用极化曲线及电化学阻抗谱（EIS）研究其腐蚀行为。结果表明,电沉积的电流密度、TiN纳米粒子的浓度、搅拌速度、溶液温度及pH值对电沉积薄膜形貌的影响较大。制备的Ni-TiNi电沉积薄膜的平均晶粒尺寸约为50nm。纳米结构的Ni-TiNi电沉积薄膜的耐腐蚀性能远优于纯Ni沉积薄膜的。     

SiC_p/2024Al铝基复合材料的耐蚀性

用电化学方法和浸泡试验研究了SiC颗粒粒度和体积分数对SiCp/ 2 0 2 4Al铝基复合材料在 3.5 %NaCl水溶液中耐蚀性的影响 ,作为比较对 2 0 2 4Al的耐蚀性也进行了研究。结果表明 ,与基体相比 ,SiCp/ 2 0 2 4Al复合材料并不增加点蚀敏感性 ,其抗蚀性与SiC体积分数和粒度有关 ,SiC颗粒体积分数低或粒度高的复合材料 ,其抗蚀性往往大。     

The corrosion behavior of carbon steel in CO2‐saturated NaCl crevice solution containing acetic acid

The corrosion behavior of X52 carbon steel electrodes in CO₂‐saturated NaCl crevice solution containing HAc was investigated by electrochemical measurements. Chemical environment measurements by Cl^? and pH microprobes show an enrichment of Cl^? ions and an increase of pH values inside the crevice. Moreover, both increments could accelerate with the decreasing dimension of the crevice mouth due to the high diffusive resistance. When the electrode in the crevice solution is coupled with the electrode in bulk solution, the alkalization and the enrichment of Cl^? ions in the crevice solution can result in a negative shift of potential of the electrode in crevice solution, while the potential of the electrode in bulk solution shifts positively during the corrosion process. Thus, a galvanic corrosion is established with the electrode in the crevice solution acting as anode while another in the bulk solution as cathode, i.e., the corrosion in the crevice solution was enhanced while the corrosion in the bulk solution was retarded. The anodic dissolution and the cathodic reduction processes dominate in the crevice solution and in the bulk solution, respectively.     

热镀锌钢表面乙烯基三乙氧基硅烷膜的腐蚀电化学行为

采用开路电位(OCP)、交流阻抗(EIS)和动电位极化法对热镀锌钢表面乙烯基三乙氧基硅烷膜腐蚀电化学行为进行了研究。结果表明,在3.5%NaCl溶液中,涂覆硅烷膜层的热镀锌钢与空白热镀锌钢相比,其低频阻抗值提高至少2个数量级,同时腐蚀电流密度减小1个数量级以上,乙烯基三乙氧基硅烷膜防腐蚀效果良好。     

Effect of Ti interlayer on corrosion behavior of nanostructured Ti/TiN multilayer coating deposited on TiAl6V4

To improve the corrosion properties of TiAl₆V₄ alloy, TiN monolayer and Ti/TiN multilayer coatings are deposited by reactive magnetron sputtering. The phase, structure, and morphology properties are investigated by grazing‐incidence X‐ray diffraction, field‐emission scanning electron microscopy, and atomic force microscopy, respectively, and the corrosion behavior is evaluated by electrochemical impedance spectroscopy and potentiodynamic polarization. The TiN monolayer and Ti/TiN multilayer with thickness of 1,350 and 1,410 nm have the (111) and (002) preferred orientation and crystallite size of 42.5 and 24.3 nm, respectively. Columnar growth in TiN is hindered by the Ti interlayers and no cracking is observed between the layers indicating strong adhesion. The nanostructured Ti/TiN coating forms stable surface titanium oxide which improves the corrosion resistance by approximately 80 and four times compared with TiAl₆V₄ alloy and TiN coating, respectively. Hindrance of the columnar structure in TiN by the Ti interlayer decreases the local corrosion rate and enhances the galvanic corrosion resistance by forming a layer on the β‐phase enriched with vanadium as well as a TiO₂ stable layer. The nanostructured Ti/TiN coating demonstrates capacitive behavior with phase angles approximately ?50° and high impedance values at low frequency to be the corrosion resistance mechanism.     

LC4铝合金剥蚀及其电化学阻抗行为

研究了LC4铝合金双级过时效处理板材在EXCO剥蚀溶液中的剥蚀行为及其相应的电化学阻抗谱。结果表明 ,腐蚀由晶界孔蚀发展为沿平行于表面的晶界腐蚀 ,并在晶界堆积大体积的楔形腐蚀产物 ,挤压表层晶粒而导致剥蚀。由于双级过时效处理使强化相 η均匀析出 ,降低了合金的晶间腐蚀程度 ,导致合金剥蚀程度很轻 ,主要表现为局部小面积的金属表层鼓泡剥蚀。剥蚀后 ,电化学阻抗谱由两个容抗弧组成 ,其中高频容抗弧源于合金原表面 ,而中低频容抗弧源于剥蚀后露出并与腐蚀介质接触的新界面。有可能根据这两个容抗成分的分析来定量判断合金的剥蚀程度。     

温度对高速电弧喷涂FeNiBSi/Cr_3C_2复合涂层热腐蚀性能的影响

采用高速电弧喷涂技术在45钢基体上制备出Fe Ni BSi/Cr3C2复合涂层.采用光学显微镜和扫描电镜分析涂层的显微结构,以及X射线衍射分析涂层相组成.试验选用摩尔比为7∶3的Na2SO4+K2SO4饱和水溶液为腐蚀介质涂刷于试样表面,并以20G钢作对比材料,在550~750℃下研究了涂层的抗热腐蚀性能.结果表明,涂层具有典型的层状结构特征,致密且连续.涂层的抗热腐蚀性能明显优于20G钢.在550和650℃下涂层表面形成了致密的氧化膜(Fe2O3,Cr2O3和Fe Cr2O4)阻碍了熔盐的侵入,提高了涂层抗热腐蚀性能.在750℃下涂层氧化膜变得不完整,不能有效地阻隔熔盐,此时涂层的抗热腐蚀性能较差.     

Effects of Al and Ni doping on oxidation and corrosion resistance of electrophoretic deposited YSZ coatings

Yttria-stablized zirconia (YSZ)/(Ni,Al) coatings were deposited on Inconel 600 alloy substrate by the electrophoretic deposition combined with vacuum sintering technique. The effects of isothermal oxidation at 1100 °C on the composition of the coatings and the crack healing were investigated, and the corrosion resistance of the coatings in 3.5% NaCl (mass fraction) solution was also studied. The results showed that the cracks on the coating gradually healed up with the increase of the isothermal oxidation time. During isothermal oxidation process, the coating composed of Ni₃Al was transformed to α-Al₂O₃ particulates. The α-Al₂O₃ particulates can seal the defects such as pores and cracks, and meanwhile prevent the oxygen diffusion into the coatings. The polarization curves and EIS results indicated that the coatings oxidized for 40 h had a more positive corrosion potential, higher breakdown potential, higher impedance module at low frequency and much lower corrosion current density compared with YSZ coated and uncoated Inconel 600 alloys.