Improvement on the Corrosion Resistance of AZ91D Magnesium Alloy by Aluminum Diffusion Coating

By combination of magnetron sputtering deposition and vacuum annealing, an aluminum diffusion coating was prepared on the substrate of AZ91D alloy to improve its corrosion resistance. The microstructure and composition of the diffusion coating was investigated by scanning electron microscopy and X-ray diffraction. The diffusion coating was mainly comprised of β phase-Al12Mg17. The continuous immersion test in 3.5 wt pct neutral NaCl solution indicated that the specimen with diffusion coating had better corrosion resistance compared with the bare AZ91D alloy specimen. The potentiodynamic polarization measurement indicated that the diffusion coating could function as an effectively protective layer to reduce the corrosion rate of AZ91D alloy when exposed to 3.5 wt pct NaCl solution.     

Fabrication of Al and Al/Ti coatings on magnesium alloy by sputtering

Multi-magnetron sputtering was applied to prepare aluminum coating and aluminum/titanium multilayer coating on AZ31 magnesium alloy. FESEM, AFM and XRD were used to investigate the morphology and phase structure of these obtained coatings. Aluminum coating presented a (111) preferred texture and this texture was strongly strengthened with the Ti(002) plane as template in Al/Ti multilayer coating. The top surface of Al/Ti-coated sample took on a round roof-like morphology compared to the pyramid-like morphology of Al-coated sample. The result of polarization tests showed that both Al coating and Al/Ti multilayer coating could improve the corrosion resistance of AZ31 magnesium alloy in 3.5 wt.% NaCl solution.     

海洋环境下热喷涂锌、铝及其合金涂层防腐蚀机理研究概况

综述了国内外几十年来在不同海水环境中对热喷涂锌铝及其合金涂层防护性能和机理研究的成果.热喷涂锌铝及其合金涂层在海洋环境中具有优良的长效防护性能,锌具有优良的电化学保护性,铝具有比锌更好的化学稳定性,锌铝合金既保留了锌的电化学特点,又具有铝的化学稳定性能.指出了今后的研究重点应该是金属与有机复合层在浪花飞溅区苛刻腐蚀环境下界面的腐蚀规律和腐蚀机理的探讨,对金属与有机复合层界面的腐蚀原因在理论上做出了本质的解释,并能预测涂层体系的防腐蚀寿命.     

Dry sliding wear behavior and corrosion resistance of NiCrBSi coating deposited by activated combustion-high velocity air fuel spray process

NiCrBSi is a Ni-based superalloy widely used to obtain high wear and corrosion resistant coatings. This Ni-based alloy coating has been deposited onto 0Cr13Ni5Mo stainless steel using the AC-HVAF technique. The structure and morphologies of the Ni-based coatings were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS). The wear resistance and corrosion resistance were studied. The tribological behaviors were evaluated using a HT-600 wear test rig. The wear resistance of the Ni-based coating was shown to be higher than that of the 0Cr13Ni5Mo stainless steel because Fe₃B, with high hardness, was distributed in the coating so the dispersion strengthening in the Ni-based coating was obvious and this increased the wear resistance of the Ni-based coating in a dry sliding wear test. Under the same conditions, the worn volume of 0Cr13Ni5Mo stainless steel was 4.1 times greater than that of the Ni-based coating. The wear mechanism is mainly fatigue wear. A series of the electrochemical tests was carried out in a 3.5 wt.% NaCl solution in order to examine the corrosion behavior. The mechanisms for corrosion resistance are discussed.     

激光熔覆CoCrFeMnNiMox高熵合金的组织和耐蚀性研究

目的 为了增强钢制结构表面的耐蚀性,研究Mo含量对CoCrFeMnNiMox高熵合金组织与耐蚀性的影响。方法 采用激光熔覆的方式在N80钢上制备CoCrFeMnNiMox（x=0.1、0.2、0.3、0.4、0.5）高熵合金熔覆层,研究Mo含量变化对高熵合金组织、物相与耐蚀性的影响。结果 CoCrFeMnNiMox熔覆试样均由单一的FCC固溶体相组成,随着Mo含量的增加,晶格畸变增大;当Mo的摩尔比超过0.3后,晶粒有长大倾向;Mo的摩尔比为0.5时,表面择优生长晶面由（111）密排晶面转变为（200）非密排晶面。熔覆试样在氯化钠溶液和稀硫酸溶液中的耐蚀性相较N80钢提升明显,其中,CoCrMnFeNiMo0.3的耐蚀性最好,在质量分数为3.5%的氯化钠溶液中其自腐蚀电流密度是N80钢的5%,自腐蚀电位比N80钢提高了1倍;在0.5 mol/L硫酸溶液中,其自腐蚀电流密度是N80钢的31%,钝化区电流密度比N80钢降低了1个数量级。结论 在该高熵合金体系中,随着Mo含量的增加,晶格畸变增大。CoCrMnFeNiMox高熵合金熔覆层可以有效地阻止基体腐蚀的发生。Mo元素在溶液中能够形成MoO3附着在金属表面,从而形成稳定致密的保护层,减少点蚀的发生。CoCrMnFeNiMo0.3熔覆层的耐蚀性最好。     

封闭对铝合金微弧氧化膜在酸性溶液中耐蚀性的影响

为了提高7A85铝合金的耐蚀性, 采用单极性正脉冲微弧氧化(MAO)技术在其表面制备了陶瓷膜层, 并采用稀土铈盐、铬酸盐和SiO₂溶胶对MAO膜进行封闭处理。采用扫描电子显微镜(SEM)、X射线衍射仪和电化学工作站研究了封闭处理对膜层表面形貌、结构和在酸性NaCl溶液中腐蚀行为的影响。实验发现, MAO膜在酸性NaCl溶液中不能有效地保护铝合金基体。稀土铈盐和铬酸盐封闭处理通过沉积水合氢氧化物封闭孔隙, 可以提高MAO膜的耐蚀性。但在酸性溶液中, 封孔物质会和H⁺发生反应而溶解, 故经封闭的MAO试样也会发生腐蚀失效。SiO₂溶胶封闭处理后MAO膜表面覆盖一层凝胶, 使膜层成为完整的致密层, 可以保护铝合金基体在酸性NaCl溶液中免受腐蚀。     

Corrosion protection and formation mechanism of anodic coating on SiCp/Al metal matrix composite

The corrosion protection from sulfuric acid anodized coatings on 2024 aluminum and SiC particle reinforced 2024 aluminum metal matrix composite (SiC_p/2024Al MMC) in 3.5 wt.% NaCl aqueous solution was investigated using electrochemical methods. The results show that the anodized coating on 2024Al provides good corrosion protection to 3.5 wt.% NaCl, and the anodized coating on the SiC_p/2024Al MMC provides some corrosion protection, but it is not as effective as for 2024Al because non-uniformity in thickness and cavities present are associated with the SiC particulates. Cavities above SiC particles are the reason that the anodized coating on the MMC cannot be completely sealed by hot water as with anodic Al alloy. SiC particle anodizes at a significantly reduced rate compared with the adjacent Al matrix. This gives rise to alumina film encroachment beneath the particle and occlusion of the partly anodized particle in the coating. It was found that the barrier layer of anodized Al MMC is not continuous, and it is composed primarily of the barrier layer of anodized Al matrix and a barrier-type SiO₂ film on occluded SiC particles in the coating. A new formation mechanism of coating growth during anodizing of a SiC_p/2024Al MMC was proposed.     

Corrosion Behavior and Protection Efficiency of 2024Al and SiCp／2024Al Metal Matrix Composite

The corrosion resistance of 2024 Al and SiC particle reinforced 2024 Al metal matrix composite(SiCp/2024Al MMC) in 3.5% NaCl solution was investigated with electrochemical method and immersion test, and the corrosion protection of sulfuric acid anodized coatings on both materials was evaluated by electrochemical impedance spectroscopy.The results showed that the SiCp/2024AlMMC is more susceptible to corrosion than its matrix alloy in 3.5% NaCl.For 2024Al,the anodized coating provides excellent corrosion resistance to 3.5%NaCl.The anodized coating on the SiCp/2024Al provides satisfactory corrosion protection,but it is not as effective as that for 2024Al because the structure of the anodized layer is affected by the SiC particulates.     

铝合金表面蓝色微弧氧化陶瓷膜的制备及性能研究

采用微弧氧化技术在5052铝合金表面制备蓝色陶瓷膜,研究Co(OH)_2着色剂浓度和微弧氧化电压对蓝色陶瓷膜组织结构和腐蚀性能的影响规律。采用光学显微镜、扫描电镜和X射线衍射研究蓝色陶瓷膜层的宏观形貌、微观组织和相结构,采用电化学工作站测试陶瓷层在3.5%(质量分数)NaCl溶液中的电化学腐蚀性能。研究结果表明,蓝色微弧氧化陶瓷层主要由γ-Al_2O_3组成,提高Co(OH)_2浓度或者氧化电压,膜层颜色由浅向深演变,当浓度增至3.0g/L后膜层蓝色不再加深,同时膜层表面逐渐封闭,致密性提高。在140V氧化电压下,添加1.0g/L Co(OH)_2所制备的蓝色膜层具有最好的耐腐蚀性能。蓝色膜具有颜色艳丽、装饰性好等优势,相信该蓝色微弧氧化膜技术在建筑材料和仪器仪表行业将会有广阔的应用前景。     

Electrochemical corrosion behavior of carbon-based thin films in chloride ions containing electrolytes

Commercially available carbon-based thin films consisting of single layers of amorphous diamond-like carbon or multilayers of crystalline TiAlN or CrN with diamond-like carbon top coatings were evaluated in relation to their electrochemical corrosion behavior in chloride ions containing electrolytes. The hardened working steel (an alloy of 0.9% C, 4.1% Cr, 4.9% Mo, 1.8% V, 6.4% W) was used as a substrate material.The potentiodynamic corrosion behavior of coated samples was tested in 3.5 wt.% NaCl solution and Hank's balanced body solution, HBBS (0.89 wt.% NaCl, further chlorides, sulfates, carbonates and phosphates). The multi-layers TiAlN + a-C:H:W and CrN + a-C:H:W exhibited only a minor improvement in corrosion resistance. Single layers of amorphous diamond-like carbon coating without hydrogen (a-C) spall off during the corrosion tests in chloride containing media. A minor improvement of the corrosion resistance is possible. The a-C:H and the a-C:H:Si, which contain hydrogen, showed the best corrosion resistance with a 100 times lower corrosion current density.     

铝锌合金在镁合金AZ91D中的扩渗机理及腐蚀性能研究

采用包埋铝和锌的方法在镁合金AZ91D表面制备了铝-锌合金化涂层,并且利用x射线衍射、能谱分析研究了该涂层的组织和耐腐蚀性能。该涂层外层为AlMg2Zn, Mg7Zn3 和Mg17Al12 金属间化合物层;内层为Mg17Al12金属间化合物分布于α-Mg晶界。研究表明,与镁合金基体相比较在质量分数为3.5wt.% NaCl扩渗层显示出较好的耐腐蚀性能。盐雾腐蚀说明,Al-Mg-Zn合金化扩渗层对于降低腐蚀速率起到有效作用。此外,合金化扩渗层与基体的结合是冶金结合,且涂层的显微硬度显著提高。     

WC-10Co-4Cr涂层在不同温度酸与NaCl溶液中的耐腐蚀性能

为提高1Cr18Ni9Ti不锈钢在NaCl和酸溶液环境中的耐磨损性能,利用等离子喷涂制备两种晶粒WC-10Co-4Cr涂层,研究其在3.5%(质量分数,下同)NaCl溶液与酸溶液(pH=5.0)中的耐腐蚀性能。结果表明:涂层中含有WC,W_2C,W以及η相(Co_xW_xC)。两种涂层在3.5%NaCl溶液中的腐蚀电位均高于1Cr18Ni9Ti基体的腐蚀电位。在不同温度酸溶液(pH=5.0)中,纳米WC-10Co-4Cr涂层的电位差随温度的变化最小。涂层在NaCl和酸溶液中腐蚀机制分别为:WC-10Co-4Cr涂层表面吸附氧粒子与涂层中的Co和WC在3.5%NaCl溶液中形成电偶;在酸溶液中(pH=5.0),涂层中的Co溶解形成Co²⁺离子,和WC相直接形成电偶腐蚀,导致涂层表面出现孤立的WC颗粒。     

Effect of aging treatment on microstructure and corrosion behavior of Al-Zn-Mg aluminum alloy in aqueous solutions with different aggressive ions

The microstructure and corrosion behavior of Al-Zn-Mg alloy(namely 7×××)after natural aging treatment(NAT)and artificial aging treatment(AAT)in aqueous NaCl solutions containing different aggressive ions have been investigated in current work.Results of microstructure characterization demonstrate that the aging treatment has a great influence on the grain size and precipitates.The grain size is relatively sizeable and no evident precipitates are observed in alloy after NAT comparable with that after AAT.The electrochemical corrosion behavior of alloy was studied by polarization curve and electrochemical impedance spectroscopy(EIS).The corrosion potential(E_corr)of the aluminum alloy is more negative in 3.5 wt.%NaCl containing 0.052 wt.%NaHSO₃solution than that in 3.5 wt.%NaCl solutions with or without 0.907 wt.%NaHCO₃.Charge transfer resistance(Rct)results reveal that alloy after AAT has an enhancement of corrosion resistance compare with that after NAT.With the immersion time increasing,mostly pitting spreads over the surface of the alloy only in NaCl solution,whereas exfoliation corrosion mainly occurs in NaCl solutions containing NaHSO₃or NaHCO₃.     

Intelligent self-healing corrosion resistant vanadia coating for AA2024

This paper is a continuation of our investigation into the designing of chromate-free anti-corrosion coatings for aluminum and magnesium based materials for marine, automotive and aerospace applications. In this paper, a simple vanadia based chemical conversion coating was applied for improving the corrosion resistance of high strength AA2024 alloy. The effect of vanadia solution concentrations (10, 30 and 50 g/l) on the corrosion behavior was investigated. EIS, linear polarization and cyclic voltammetry techniques were used to evaluate the electrochemical behavior in 3.5% NaCl. Vanadia coatings prepared by dissolving 10 g of vanadate salt per liter showed the best localized corrosion resistance as measured by EIS and polarization techniques. The optimum conditions to obtain corrosion protective coatings for AA2024 were determined. Surface examination of the samples was investigated using AFM, SEM-EDS and macroscopic images.     

Study of the corrosion behavior of zinc and Zn–Co alloy electrodeposits obtained from alkaline bath using direct current

The corrosion behavior of Zn and Zn–Co alloy electrodeposits that were obtained from weakly alkaline glycine solutions has been studied. SEM, EDS and XRD were used to study surface morphology, chemical composition and phase structure of the coatings. Corrosion behavior of Zn and Zn–Co alloy coatings was studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. The results showed that increasing current density during deposition, increases cobalt content of the coating. It was also shown that increasing current density, up to 15 mA cm⁻², decreases the grain size and further increase in current density increases the grain size of the deposit. It was also noticed that corrosion resistance of deposits was highly influenced by the composition and morphology of the coatings. Zn–Co deposit containing 0.89 wt.% Co showed the highest corrosion resistance due to its single phase structure and its finer morphology.     

LY12铝合金铈化学转化膜的结构及耐蚀性研究

应用电化学方法及腐蚀试验研究了LY12铝合金表面常温稀土化学转化膜。结果表明，铝合金的稀土化学转化膜具有成膜温度低、速度较快、膜的耐蚀性能好等优点。电位－时间曲线表面，成膜动力学包括铝合金的溶解及随后的成膜两个过程。SEM表明，铝合金稀土化学转化膜的形态为片状，EDAX能谱表明转化膜主要由Ce,O,Al及少量的促进剂离子组成。腐蚀试验表明，未经处理的铝合金在3．5%NaCl溶液中经过21天浸泡后，表面出现了严重的点蚀，而经稀土处理的铝合金经过相同时间的浸泡后，表面只发生了轻微的均匀腐蚀，而未发生点蚀，浸泡后稀土处理的铝合金的失重较空白试样的下降了近1倍，铝合金的耐蚀性能大大提高。     

机械镀Zn-Al合金镀层的耐腐蚀性能研究

为了增强机械镀镀层的耐腐蚀性能,采用机械镀方法,以含铝5%(质量分数)的Zn-Al合金粉为原料,在Q235钢材基体表面制备了Zn-Al合金镀层。利用扫描电镜(SEM)表征了合金镀层的截面和断面形貌;采用极化曲线、电化学阻抗谱(EIS)分析了合金镀层在3.5%NaCl溶液中的电化学行为;通过中性盐雾腐蚀实验分析了合金镀层的耐蚀性,并采用XRD分析了镀层的盐雾腐蚀产物。结果表明,Zn-Al合金镀层由葫芦状的Zn-Al合金颗粒交错互嵌堆积而成,镀层颗粒之间以类似隼接的连接方式搭接“卡锁”;与机械镀Zn层相比,Zn-Al合金镀层的腐蚀电位正移了209 mV,腐蚀电流密度仅为纯Zn镀层的7.1%左右,极化电阻为纯Zn镀层的14倍;Zn-Al合金镀层的容抗弧半径明显大于纯Zn镀层的弧半径,且Q_dl较纯锌层减小;纯Zn镀层出现白锈和红锈的时间分别为24和362 h,而Zn-Al合金镀层出现白锈和红锈的时间为48和504 h。Zn-Al合金镀层的耐中性盐雾腐蚀性能明显优于纯Zn镀层,合金镀层对电荷转移具有更好的抑制作用,且Zn-Al合金镀层的腐蚀产物结构致密,可增强物理屏蔽功能。     

含碳纳米管有机无机复合涂层的制备与防护性能

为了改善铝合金材料的耐腐蚀性能, 研究了以正硅酸乙酯（TEOS）为主要原料, 加入一定量的KH-550, 并引入部分羟基化的多壁碳纳米管（MWCNTs-OH）进行复合, 以冰乙酸为催化剂, 采用溶胶---凝胶法在铝合金基体表面形成复合涂层。腐蚀电化学测试和扫描电镜分析结果表明, MWCNTs-OH的引入能够明显提高涂层的防护性能, 并有效防止涂层开裂。考察了MWCNTs-OH含量和热处理温度对涂层性能的影响。结果表明: MWCNTs-OH质量分数为0.04%、 热处理温度为130℃时制备的涂层性能最佳, 相应的试样在3.5wt%NaCl溶液中的腐蚀电流密度约为3.056×10-8A/cm2, 而同等实验条件下铝合金基体腐蚀电流密度为7.216×10-5A/cm2, 涂层的存在使腐蚀速率降低了3个数量级, 涂层对铝合金基体具有显著的防护效果。      

基于工业合金激光熔覆制备Fe基非晶涂层

以FeCoCrMoCBY块体合金为熔覆材料,采用激光熔覆在低碳钢表面制备非晶涂层,探讨不同激光功率对涂层成形及组织的影响,通过显微硬度仪、电化学工作站测试涂层显微硬度及耐腐蚀性能。研究结果表明,其他参数不变,激光功率为17.6~20.8 W时,涂层成形良好,与基材呈典型冶金结合。随激光功率增加,涂层稀释率升高,裂纹倾向增大,非晶化程度降低。激光功率为17.6 W时,涂层主要由非晶组成,稀释率低于24.2%,结构致密,包括热影响区、熔合区和熔覆区;涂层平均显微硬度为1 330HV,约高于基材9倍,在3.5%NaCl溶液中的耐腐蚀性能明显优于316L不锈钢。     

Deposition and corrosion behavior of silicate conversion coatings on aluminum alloy 2024

Potassium silicate was deposited on AA2024 aluminum alloy as environmentally friendly conversion coatings and its corrosion behavior were examined by means of electrochemical impedance spectroscopy, potentiodynamic polarization and surfaces techniques. Potentiodynamic polarization curves show significant decrease in corrosion current density of silicate coated aluminum in NaCl solution. The corrosion resistance was increased with increasing silicate concentration of coating baths. The results indicated that the coating applied from 3 molar silicate baths is more uniform and continuous. The X‐ray diffraction (XRD) and energy discharge spectroscopy (EDS) spectra confirm the existence of silicate film on the AA2024 surface. The coating performance was evaluated in acidic and basic NaCl solution and the results show the stability of silicate conversion coating in these solutions.