Research on the Structure and the Corrosion Resistance of Zn-Co Alloy Coating

In this paper, by using XRD and XPS the composition and the structure of Zn-Co alloy coating containing Co 0.6%–0.8% and its corrosive products have been investigated analytically; a comparison of corrosion resistance between the alloy coating and conventional zinc coating has been performed; and finally the mechanism of its high corrosion resistance has been presented and discussed.     

Electrodeposition of zinc on AZ91D magnesium alloy pre‐treated by stannate conversion coatings

A stannate chemical conversion process followed by an activation procedure was employed as the pre‐treatment process for AZ91D magnesium alloy substrate. Zn was electroplated onto the pre‐treated AZ91D magnesium alloy surface from pyrophosphate bath to improve the corrosion resistance and the solderability. The surface morphologies of conversion coating and zinc coating were examined with scanning electron microscope (SEM). The phase composition of conversion coating was investigated by X‐ray diffraction (XRD). The electrochemical corrosion behavior of the coatings in the corrosive solution was investigated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). The experimental results showed that the activated stannate chemical conversion coating provided a suitable interface between zinc coating and the AZ91D magnesium alloy substrate. The corrosion resistance of the AZ91D substrate was improved by the zinc coating.     

Al/Cr复合涂层对Ti2AlNb合金抗热腐蚀性能的影响

目的改善Ti2AlNb合金在高温腐蚀盐环境中的耐热腐蚀性能。方法在Ti2AlNb合金表面通过双层辉光等离子渗铬及磁控溅射镀铝技术制备Al/Cr复合涂层,分析涂层热腐蚀前后的微观形貌和物相组成,并探究涂覆Na2SO4盐膜的试样在不同温度下(750、850、950℃)的热腐蚀行为。结果Al/Cr复合涂层组织均匀致密,且与基体结合良好,厚度约73μm,由表及里依次由Al沉积层、Al/Cr合金层、Cr沉积层、Cr扩散层四部分组成。经不同温度Na2SO4盐热腐蚀后,Al/Cr复合涂层腐蚀程度均显著小于合金基体。涂层试样经750~850℃Na2SO4盐热腐蚀后质量变化较小,850℃腐蚀增重仅0.525 mg/cm^2,而经历950℃、40 h熔盐热腐蚀后失重达到73.571 mg/cm^2,且试样截面出现剥离、脱落现象,Al/Cr复合涂层抵抗热腐蚀能力减弱。结论具有涂层保护的试样抗热腐蚀性能明显优于合金基体。Al/Cr复合涂层在750~850℃Na2SO4盐环境中具有良好的热腐蚀抗力,而更高温度段(850~950℃)的热腐蚀抗力下降。Al/Cr复合涂层在Na2SO4盐环境中良好的抗热腐蚀性得益于涂层中Al、Cr元素氧化形成以Al2O3、Cr2O3为主的混合氧化膜,有效阻碍外界氧气及腐蚀性介质侵入基体。     

NiCrBSi超音速火焰喷涂层在水溶液中的腐蚀行为

采用高速氧燃料火焰喷涂(HVOF)方法在普通碳钢表面制备了镍基合金涂层，对其组织结构进行了观察，并利用电化学方法对其在水溶液中的腐蚀行为进行研究，探讨HVOF涂层应用于水介质环境中的可能性．试验结果表明：NiCrBSi喷涂层在1mol／L NaOH溶液中表面能够形成致密钝化膜，耐碱腐蚀的性能最好．涂层在酸性溶液中的腐蚀速度大于在中性3．5％NaCl溶液中的腐蚀速度。利用冰醋酸将3．5％NaCl溶液的pH值调整到3，可以提高实验结果的重现性。酸性溶液中，只要被测试表面处于活性溶解状态，腐蚀试验重现性都能满足要求。另外，缺陷越少涂层的耐蚀性越好，减少涂层中的孔隙等缺陷是提高涂层耐蚀性的关键。     

Effect of enamel coating on long-term oxidation and hot corrosion behavior of Ti-24Al-17Nb-0.5Mo alloys

The effect of enamel coating on long-term isothermal oxidation at 700 ℃ and cyclic oxidation at 800 ℃ in air and hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo in 75% (Na2SO4 K2SO4 ) 25% NaCl (mass fraction) molten mixed salts at 700 ℃ was investigated. The results indicate that Ti-24Al-17Nb-0.5Mo alloy exhibits relatively poor long-term oxidation resistance due to the formation of Al2O3 TiO2 Nb2O5 mixed scales and poor hot corrosion resistance due to the spallation of scales formed in molten (Ns, K)2 SO4 NaCl. Enamel coating can effectively protect Ti-24Al-17Nb-0.5Mo alloy from long-term oxidation at high temperature in air and remarkably improve the hot corrosion resistance of Ti-24Al-17Nb-0. 5Mo alloy, and can act as the barrier to suppress the migration of oxygen and corrosive ions into the substrate.     

铝合金上电弧离子镀(Ti,Al)N膜的腐蚀特性

研究铝合金上电弧离子镀(Ti,Al)N膜层的腐蚀性能。通过对3种N2气分压下沉积膜层的阳极极化曲线、电化学阻抗谱、盐雾腐蚀失重曲线以及表面形貌的分析表明:沉积过程氮分压较低时,膜层中含有富金属相,耐腐蚀性能较低;增加氮分压使膜层中金属与非金属呈理想配比时,膜层的耐腐蚀性明显增加;膜层在缺陷处产生点蚀、电偶腐蚀,并通过形成裂纹、碎屑脱落使质量显著减小。     

镁合金等离子喷涂Al/Al_2O_3涂层的耐腐蚀性能

采用等离子喷涂技术在AZ31镁合金表面制备Al/Al_2O_3复合涂层,测试了镁合金及表面喷涂有Al/Al_2O_3复合涂层的镁合金试样的极化曲线,研究了没有涂层、经封孔处理和未经封孔处理的喷涂有复合涂层的镁合金三种试样在浸泡腐蚀和5%NaCl盐雾腐蚀情况下的耐腐蚀性能及其腐蚀行为.结果表明,经封孔处理的Al/Al_2O_3复合涂层镁合金试样在上述腐蚀条件下的耐腐蚀性均优于镁合金和涂层未封孔处理的试样,在浸泡试验中未封孔处理的涂层试样比镁合金腐蚀更加严重,在盐雾试验中却优于镁合金.     

The properties of electrodeposited Zn-Co coatings

The possibility of increasing the corrosion resistance of automotive sheet steel by electrodepositing with Zn-Co alloy coatings was investigated. Process variables during electrodeposition such as current density, electrolyte flow rate, and pH were varied in order to examine their influence on the electroplating process. Cobalt contents varying from 0.2 to 7 wt% were easily obtained. The influence of these process parameters on the characteristics of the coating could be related to the hydroxide suppression mechanism for anomalous codeposition. The structure and the morphology of the coatings were determined using SEM and XRD analysis. Application properties important for coating systems used in the automotive industry, such as friction behavior, adhesion, and corrosion behavior, were investigated on coatings with varying cobalt content. The corrosion resistance of the Zn-Co alloy layers was found to be better than that of pure zinc coatings.     

Increasing the wear and corrosion resistance of magnesium alloy (AZ91D) with electrodeposition from eco-friendly copper- and trivalent chromium-plating baths

Mg alloy, AZ91D, which has a two-phase structure, was successfully electroplated in an alkaline Cu-plating bath. The Cu-coated Mg alloy specimen was further electroplated in eco-friendly acidic Cu and then trivalent Cr baths to obtain an anti-wear and anti-corrosion Cr/Cu coating. Experimental results show that the wear and corrosion resistance of the Mg alloy specimen was considerably improved by trivalent Cr electrodeposition. The hardness of the as-plated Cr deposit was drastically increased by using reduction-flame heating for 0.5 s. The above-mentioned results were measured via bonding strength, hardness, wear and corrosion tests. A superior wear and corrosion resistance was obtained when a Cu-coated Mg alloy specimen was electroplated with a trivalent Cr deposit, followed by heating with reduction-flame heating for 0.5 s.     

KCJ-15扬雪机搅笼镍基喷熔复合涂层的研究

目的在KCJ-15型扬雪机搅笼NiCrBSiC合金涂层的基础上,添加硬质碳化钨颗粒,并研究其在搅笼基体上的腐蚀、磨损规律。方法制备7组碳化钨颗粒含量不同的镍基复合粉末,分别在不同腐蚀液体中进行摩擦磨损实验,随后选取抗磨性能最佳的一组,分别进行不同载荷和不同滑动速度下的摩擦磨损试验。结果在同一种腐蚀液体中,喷熔层的摩擦系数随碳化钨含量的增加变化不大,磨损率随碳化钨含量的增加先减小后增大,其中浸泡在HCl和NaCl溶液中的试块喷熔层的摩擦系数和磨损率普遍偏高,而浸泡在NaOH和H_2SO_4溶液中的试块喷熔层的摩擦系数和磨损率普遍偏低。随着载荷的增加,喷熔层的摩擦系数和磨损率增大。随着滑动速度的增加,喷熔层的摩擦系数增大,磨损率降低。结论在KCJ-15型扬雪机搅笼NiCrBSiC合金涂层中,添加碳化钨的最佳质量分数在15%~25%之间,此时可获得最佳的抗磨性能。此外,喷熔层的摩擦系数受到腐蚀液体、外部载荷和滑动速度的影响较大,受碳化钨含量的影响较小。     

激光熔覆Ni2Si／Ni3Si2金属硅化物合金涂层显微组织与耐蚀性

以Ni76Si24（质量百分数）合金粉末为原料，利用激光熔覆技术在A3钢表面制得了组织由条件Ni2Si初生相及少量Ni2Si/Ni3Si2共晶组成的新型金属硅化物合金涂层，分析涂层显微组织并测定其在0．5mol/1 H2SO4水溶液及不同浓度NaCl水溶液中的阳极极化曲线，结果表明激光熔覆Ni2Si/Ni3Si2金属硅化物合金涂层表面平整，组织细小，与基体为完全冶金结合，同时由于涂层的组织组成相Ni3Si2本身均具有极好的耐蚀性并具有快速凝固细小均匀的显微组织，该激光熔覆Ni2Si/Ni3Si2金属硅化物合金涂层在0．5mol/l H2SO4及3．5％NaCl水溶液中均具有优良的耐蚀性能。     

水性Al-Zn-Si合金涂层微观组织及腐蚀性能研究

用Al-Zn-Si合金粉末制备热烧结铝锌硅合金涂层,通过盐水浸泡实验和电化学测试研究其耐蚀性能,并结合扫描电镜和X射线衍射分析等手段观察Al-Zn-Si合金涂层显微组织及其在盐水中的腐蚀产物形貌,分析涂层的耐蚀机理。结果表明,Al-Zn-Si合金涂层也具有阴极保护作用,且Al-Zn-Si合金延缓涂层金属粉末的消耗,使牺牲阳极的腐蚀速率减慢。     

Process Optimization for Cerium Oxide Based Conversion Coating of AZ91D Magnesium Alloy at Room Temperature

The Ce2SO4/H2O2 containing solution is used to prepare a chrome-free cerium oxide based chemical conversion coating on AZ91D magnesium alloy at room temperature,and an orthogonal experiment was carried out to optimize the treating process.The effect of preparing parameters on the coating growth and the corrosion resistance were studied.It was found that H2O2 is the dominant influence factor on the coating weight gain in the orthogonal experiment,with Ce(SO4)2 coming next and immersion time having the least impact,while the most dominant influence factor on the corrosion resistance is Ce(SO4)2,with H2O2 coming next and immersion time having the least impact.The coating has the best corrosion resistance,treated in the solution of 10 g/l Ce(SO4)2 and 12 ml/l H2O2 for 4 min.SEM was adopted to study the micro-morphology of the conversion coating on magnesium alloy surface The prolonged immersion time duration or the increased concentration of Ce(SO4)2 and H2O2 will increase the coating thickness,but tiny cracks appears resulted from the fast coating deposition.     

脉冲电化学沉积羟基磷灰石涂层改善Mg-Nd-Zn-Zr合金在模拟体液中的耐腐蚀性能

采用脉冲电化学沉积的方法,在新开发的Mg-Nd-Zn-Zr合金(JDBM)表面制备出了羟基磷灰石(HA)涂层,并对其耐蚀性能和血液相容性进行了研究.结果表明,表面改性后的JDBM镁合金具有更好的耐腐蚀性能,腐蚀后涂层保持了良好的完整性,析氢试验也表明涂层对基体在仿生腐蚀环境中有一定的保护作用,且不会引起模拟体液pH值较...     

Corrosion of coating materials in oxidizing and hydrogen chloride containing atmospheres

The boiler tubes in waste incinerator plants and power plants are mainly corrosive strained. This paper presents the corrosion behaviour of various coating materials in two corrosive atmospheres at 500°C. In a first test, Ni‐based materials applied by High Velocity Oxygen Fuel Flame (HVOF)‐spraying and Atmospheric Plasma Spraying (APS) as well as Cr‐based materials obtained by diffusion coating process are tested in oxidizing atmosphere with water saturation. The results of the corrosion test in this H₂O‐O₂‐N₂‐atmosphere show that NiCr applied by HVOF is less oxidized than that applied by APS‐coating, whereas NiCrBSi coating by APS shows higher resistance than that applied by HVOF‐spraying. The diffusion coating of Cr/Si is better than that of pure Cr. In a second test, metallic Mo and W‐based materials applied by thermal spraying are tested to verify their corrosion resistance in HCl‐H₂O‐O₂‐N₂‐atmosphere. It is shown that pure Mo applied by APS on 13 CrMo 44 and WCrNi sprayed on 15 Mo 3 by HVOF as well as on 13 CrMo 44 show relatively high corrosion resistance, whereas Mo sprayed by APS on 15 Mo 3 is not resistant. Both tungsten‐cobalt‐chromium mixtures show extremely high oxidation rates. Base materials in both tests were the standard boiler tube materials 15 Mo 3 and 13 CrMo 44. But even the low corrosion rates of the best materials in these tests are higher compared to those of materials already presented by Cha et al. in an earlier paper.     

电弧喷涂Zn-22Al-Mg-RE合金涂层的耐蚀性能

采用电弧喷涂技术和自主研发的合金丝材在Q345基体上制备出Zn-22Al-Mg-RE合金涂层。通过SEM、铜加速乙酸盐雾试验、XRD和极化曲线来比较纯锌涂层和Zn-22Al-Mg-RE合金涂层的微观结构及耐蚀性能。结果表明,Zn-22Al-Mg-RE合金涂层相比于纯锌涂层结合强度提高了40%,在铜加速乙酸盐雾试验中出现第一锈点的时间延长1倍以上。电化学实验结果也表明合金涂层具备更优异的耐蚀性能。研究认为,Zn-22Al-Mg-RE合金涂层腐蚀产物中出现大量稳定致密的Zn6Al2(OH)16CO3·4H2O物相,是耐蚀性能提高的主要原因之一。     

等离子喷涂工艺对锅炉管束用Fe 基非晶涂层组织结构和耐蚀性能的影响

目的研究等离子喷涂功率和喷涂时间对锅炉管束用Fe基非晶涂层的相组成、微观组织结构及涂层耐蚀性能的影响。方法通过X射线衍射、扫描电子显微镜和三电极电化学研究进行分析。结果涂层主要由非晶相组成,表面较为平整致密;随着喷涂功率和喷涂时间的增加,涂层非晶相含量降低,孔隙率降低,致密性升高。非晶涂层在0.5mol/L H2SO4溶液和在3.5%(质量分数)NaCl溶液中均表现出良好的钝化作用,在0.5mol/L H2SO4溶液中钝化区较宽,在3.5%NaCl溶液中自腐蚀电流密度较低。随喷涂功率和时间的增加,阳极极化曲线钝化区加宽,电流密度降低。结论喷涂功率升高会导致涂层孔隙率下降,喷涂时间增加则致使涂层厚度增加,腐蚀介质渗透到基体的表面路径和阻力增加,从而可以进一步改善Fe基非晶涂层的耐蚀性能。     

锆合金在HCl和H2SO4溶液中的耐蚀性能研究

采用化学浸泡、电化学测试和物理检测技术,研究了HCl和H2SO4溶液中锆合金的腐蚀行为.结果表明,锆合金在还原性的HCl和低浓度H2SO4溶液中,具有优异的耐蚀性,而在高浓度的氧化性H2SO4溶液中腐蚀速率显著增大.物理检测结果显示,腐蚀的锆合金表面均匀地覆盖着弥散分布的微小颗粒状ZrO2.还原性的HCl和低浓度H2SO4溶液中ZrO2膜保持了原有的致密性,增强了锆合金的耐蚀性能.而高浓度H2SO4溶液中,在其强氧化作用下,锆合金基体/膜界面处不断生成ZrO2.当膜增加到一定厚度时,氧化膜的晶格参数与金属的晶格参数不一致,产生内应力,降低了氧化膜的附着力,直至氧化膜破裂,露出新鲜的锆合金表面.继之,新鲜的锆合金再次被氧化,以此循环往复,导致锆合金在浓H2SO4溶液中腐蚀加剧.     

铝合金用的两种有机防护涂层评价

    选用LD5、LY11、ZL402为基材,分别施涂IMR11纳米浓缩浆复合涂层(纳米涂层)和SEBF-2型改性熔融结合环氧粉末复合涂层(环氧涂层),利用拉伸试验、抗弯试验以及铜加速乙酸盐雾腐蚀试验,研究涂层在应力应变条件下和酸性盐雾条件下与基材铝合金的适配性.结果表明：纳米涂层比环氧涂层与铝合金基材有更好的适配性;适合用于工作在海洋环境中的飞机、船舶、车辆等非磨损条件下动力设备铝合金结构件的防护涂层.     

镁合金表面防腐蚀超疏水涂层制备研究进展

镁合金是一种有发展前途的绿色工程金属材料，但其较差的抗腐蚀性能限制了它的大规模应用。对镁合金表面进行超疏水处理，能够极大地提高镁合金的耐腐蚀性能。当超疏水试样浸泡在腐蚀溶液中时，该结构将在腐蚀介质中形成固-气-液界面层，减少镁合金表面与腐蚀介质之间的接触面积，从而降低腐蚀速度。超疏水表面需要满足微纳米结构和低表面能2个必要条件。可以采用二步法或一步法在镁合金表面制备超疏水表面，详细介绍了在镁合金表面构造微纳米结构的方法，包括激光处理、机加工、化学刻蚀、化学镀、电化学沉积、阳极氧化、微弧氧化、水热合成和喷涂等方法。超疏水表面一旦受到机械损伤，微纳米结构无法满足条件，超疏水表面的“气垫效应”消失，腐蚀介质就会直接与微纳米结构接触，因此需要保证构建的微纳米粗糙结构对镁基体具有良好的保护作用并具有自愈功能。通过制备复合涂层，提高下层微纳米结构的自愈合性能，上层涂层的超疏水性与下层涂层的良好物理屏障能力的协同效应可以改善涂层的长久耐腐蚀性能。综述了在镁合金上制备具有良好耐腐蚀性能的复合超疏水表面的方法，并对镁合金超疏水表面防护技术的研究方向进行了展望。