Corrosion behavior of Cr electrodeposited from Cr(VI) and Cr(III)-baths using direct (DCD) and pulse electrodeposition (PED) techniques

A comparison was made between the electrochemical corrosion behaviors of chromium deposited from hexavalent [Cr(VI)] and trivalent [Cr(III)] chromium baths using direct current (DCD) and pulse electro deposited (PED) techniques. Chromium coatings were deposited on mild-steel (MS) substrate. The corrosion behavior of both DCD and PED chromium from Cr(VI) and Cr(III)-baths in 3.5%NaCl solution was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results indicated that PED chromium from Cr(VI) and Cr(III)-baths have higher charge-transfer resistance R_ct and very low I_corr than that of DCD chromium on mild-steel substrate.     

超音速火焰喷涂FeCrSiB涂层的腐蚀行为

采用超音速火焰(high velocity oxygen fuel,HVOF)喷涂技术在Q235钢基体上制备了FeCrSiB合金涂层.利用X射线衍射仪、扫描电子显微镜、电化学工作站等设备对涂层的显微组织结构和耐腐蚀性进行了研究.结果表明,采用HVOF喷涂技术制备的FeCrSiB涂层结构致密,孔隙率为0.65%,与基体结合良好.FeCrSiB涂层在3.5%NaCl溶液、1 mol/L HCl溶液和1 mol/L NaOH溶液中都经历了活性溶解-钝化-过钝化的过程,且该涂层在3.5%NaCl溶液和1 mol/L HCl溶液中的耐腐蚀性能要优于镀铬层,在1 mol/L NaOH溶液中的耐腐蚀性能低于镀铬层.     

等离子弧堆焊WC增强型高铬铸铁的组织和性能

采用等离子弧粉末堆焊技术在Q235钢表面分别堆焊高铬铸铁和WC增强型高铬铸铁,通过对各堆焊层的显微组织、化学成分、显微硬度、耐磨性和耐蚀性进行对比分析,揭示WC颗粒对高铬铸铁堆焊层的影响。结果表明,高铬铸铁堆焊层显微组织由初生(Fe,Cr)7C3和共晶组织组成,WC增强型高铬铸铁堆焊层由初生碳化物、WC颗粒和共晶组织组成。与高铬铸铁相比,WC增强型高铬铸铁由于WC的加入,初生碳化物面积分数非常高,共晶组织数量相应减少;WC增强型高铬铸铁的硬度,耐电解腐蚀性和耐热腐蚀性均优于高铬铸铁。两种堆焊层熔合线处的硬度陡降,结合线扫描结果说明,WC的加入不影响WC增强型高铬铸铁堆焊层与基体界面处的冶金结合和堆焊质量。     

硫酸铈对三价铬钝化膜耐腐蚀性的影响研究

目的研究硫酸铈对三价铬钝化膜耐蚀性能的影响。方法通过在三价铬镀铬盐溶液中分别添加0.3、0.5、0.8、1.0、1.5 g/L的硫酸铈,然后通过极化曲线测试,对比不同硫酸铈添加量的钝化膜的腐蚀电流密度,确定硫酸铈在三价铬镀铬盐溶液中的最佳添加量,然后分别制备未添加硫酸铈和添加最佳添加量硫酸铈的三价铬钝化膜,通过电化学工作站CHI660E测量Tafel极化曲线和电化学阻抗谱。分析钝化膜的电化学性能,研究不同钝化膜的耐腐蚀性。观察试样表面的微观形貌,对比添加硫酸铈和未添加硫酸铈的钝化膜的微观形貌。结果通过极化曲线测试发现,当硫酸铈的添加量为1.0 g/L时,钝化膜的腐蚀电流密度小于其余添加量的钝化膜,添加硫酸铈和未添加硫酸铈的钝化膜的耐蚀性能不同,添加硫酸铈后的钝化膜性能得到改善,且钝化膜膜层的微观形貌发生改变。结论添加硫酸铈后,三价铬钝化膜的耐腐蚀性能增强。当硫酸铈的添加量为1.0 g/L时,腐蚀电流密度最小,为3.835×10~(-6) A/cm~2,耐腐蚀性能优于其余钝化膜。     

取代装饰铬的纳米Sn-Co-X合金

装饰铬在全世界的市场需求量是硬铬的3倍,长期以来镀铬工艺是众所周知的有毒工艺,由于电镀纳米Sn-Co-X合金具有与Cr6+非常接近的颜色及更好的耐腐蚀性,且对环境和人体安全,是取代Cr6+与Cr3+的极好选择。纳米Sn-Co-X的耐腐蚀性优于Cr6+和Cr3+,更优于常规晶态的Sn-Co合金。用扫描电镜(SEM)、透射电子显微镜(TEM)、X射线光电子能谱仪(XPS)和原子发射光谱(AES)对纳米Sn-Co-X合金的微观结构及腐蚀前后的表层变化进行了分析,阐述了纳米Sn-Co-X合金优异的耐腐蚀性机理。     

TiN Coatings Modified by an Interlayer of Electroplated Chromium on Mild Steel

TiN films on mild steel were deposited by reactive d.c. magnetron sputtering: electroplated chromium was incorporated as an interlayer. Surface hardness, measured by the Knoop indentation method under a load of 25 gf, phase analysis by the X-ray diffraction method and corrosion behaviour by the potentiodynamic measurement technique of these coatings have been evaluated. Surface hardness values were found to increase from about 1000–1100 for TiN coatings on mild steel to about 1800–1900 (HK₂₅) for TiN coatings with chromium as interlayer. Potentiodynamic corrosion tests, performed in IN H₂SO₄ solutions, have shown that with a chromium interlayer the corrosion resistance increases significantly as compared to TiN only sputtered coatings on mild steel samples. No spoiling of TiN coatings was observed during full sweep voltage of -1000 mV to +1000 mV when they were tested with a chromium interlayer.     

热模钢渗氮与30SiMn2MoVA镀铬性能比较

30SiMn2MoVA钢作为我国传统轻武器身管用钢,逐渐不能满足现代武器的要求,内膛镀铬处理带来的问题也急需解决。选用一种新研发的具有良好室温、高温和低温强韧性匹配的热模钢25Cr3Mo2NiSiWVNb,结合其合金元素种类,通过盐浴渗氮进行表面改性,并与30SiMn2MoVA镀铬进行比较。开展了30SiMn2MoVA镀铬和热模钢渗氮后组织形貌观察、硬度检测以及热模钢渗氮前后物相变化的分析,并针对身管储存要求及实际射击工况,对两种试样的耐蚀性和耐高温磨损性能进行比较。结果表明:热模钢渗氮后硬度高于镀铬层,在3.5%NaCl溶液中耐腐蚀性能与镀铬层相当,但是耐高温磨性能仍需要进一步提升。     

直流和高功率磁控溅射制备氮化铬薄膜及其结构性能比较

目的 比较直流磁控溅射（DCMS）和高功率磁控溅射（HiPIMS）两种沉积技术制备的氮化铬（CrN）薄膜的结构和性能。方法 采用DCMS和HiPIMS沉积技术,在金属镍（Ni）基底上沉积CrN薄膜,采用X射线衍射（XRD）、扫描电镜（SEM）和显微硬度计等仪器,分析CrN薄膜的晶相结构、表面以及截面形貌、基底与薄膜复合硬度、摩擦性能等。结果 XRD晶体测量显示DCMS制备的CrN薄膜在(111)晶面择优生长,内应力大;而HiPIMS制备的CrN薄膜为(200)晶面择优生长,内应力小。SEM显示两种方法制备的CrN薄膜都呈柱状晶体结构生长,但HiPIMS沉积的CrN薄膜颗粒尺寸较小,柱状晶体结构和晶粒更致密。硬度测量得到HiPIMS制备的CrN薄膜显微硬度为855.9HV,而DCMS制备的CrN薄膜显微硬度为501.5HV。此外,DCMS制备的CrN薄膜平均摩擦系数为0.640,而HiPIMS制备的CrN薄膜摩擦系数为0.545,耐磨性也好。HiPIMS制备的CrN薄膜的腐蚀电流比DCMS制备的CrN薄膜低1个数量级。结论 HiPIMS沉积技术制备的CrN薄膜颗粒尺寸小,结构更致密,且缺陷少、硬度高、防腐蚀性好,薄膜各项指标都优于DCMS沉积的CrN薄膜。     

Composition,structure, and corrosion properties of coatings of Co-W alloys electrodeposited under direct current

A correlation has been found between the composition, structure, and corrosion resistance of electrolytic Co-W coatings (on the basis of voltammeter and impedance measurements at pH-6.0 in a chloride-sulfate model solution) deposited at various densities of direct current from citrate electrolyte with a high concentration of sodium tungstate with addition of boric acid at a temperature of 58°C. It is found that these coatings possess a high corrosion resistance that is only insignificantly inferior to that of electrolyte chromium coatings. We have determined the interval of current densities of electrodeposition in which corrosion resistance of the coatings is maximum.     

A new method for electroless Ni-P plating on AZ31 magnesium alloy

Coating Ni-P films on AZ31 magnesium alloys via electroless plating and organic coatings (organsilicon heat-resisting varnish), was studied. An organic coating was proposed as the interlayer between Ni-P coating and AZ31magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The Ni-P deposited on the interlayer was also characterized by its structure, morphology and corrosion-resistance. The interlayer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. The result of the cross-cut test indicates the adhesion between the substrate and the interlayer is good enough. A Ni-P film with fine and dense structure was obtained on the AZ31 magnesium alloy. The electrochemical measurements show that the sample with Ni-P film exhibits lower corrosion current density and more positive corrosion potential than the substrate. Furthermore, the Ni-P coating on the AZ31 magnesium alloy exhibits high corrosion resistance in the rapid corrosion test illustrated in this paper. The method proposed in this work is environmentally friendly: no fluoride or hexacalent chromium compounds are used. In addition, it provides a new concept for plating the metals, which are considered difficult to plate due to high reactivity.     

铬对低碳高铬铸铁性能的影响

通过力学性能、疲劳磨损及腐蚀磨损性能测试以及金相组织观察,研究了铬含量对低碳高铬铸铁性能的影响.结果表明,随着含铬量的增加冲击韧度降低;硬度随着含铬量的增加,先上升,而后降低;疲劳磨损率在w(Cr)≤27.5%时较低;腐蚀磨损率在w(Cr)=17.5%～27.5%时较低;w(Cr)=17.5%时低碳高铬铸铁的综合性能最好.     

硫酸盐电镀三价铬镀层性能研究

为对硫酸盐体系三价铬镀层性能进行更深入的了解,分析了电镀时间对镀层厚度、表面形貌和镀层耐蚀性的影响.采用X射线荧光光谱仪、体视显微系统对镀层厚度和形貌进行了测试;通过CASS试验、Tafel曲线和EIS曲线测试,对采用不同电镀时间制备的三价铬镀层及六价铬镀层的耐蚀性进行了分析.试验结果显示:三价铬镀层厚度基本随电镀时间的增加而线性增加;电镀时间达到10min时,镀层表面形貌由微孔变为微裂纹状,镀层耐蚀性最好;硫酸盐体系三价铬镀层的耐蚀性与六价铬镀层的耐蚀性相当.可见,硫酸盐体系三价铬镀层具有优良的耐蚀性.     

镀锌层三价铬黑色钝化膜的耐蚀性能

制备了一种环保、不含六价铬的三价铬黑色钝化液,选择适当的封闭剂,研究其在镀锌层表面钝化后的耐腐蚀性能。通过醋酸铅点滴试验、塔菲尔极化曲线测试、电化学阻抗测试检测钝化膜的耐蚀性及采用扫描电子显微镜观察其表面形貌。结果表明:镀锌层表面经三价铬黑色钝化后再进行封闭处理,弥补了Cr3+钝化后无自愈能力的缺点,显著提高了镀锌层钝化膜的耐腐蚀性能,而且达到了Cr6+黑色钝化的外观效果。     

Electroless Ni-P layer with a chromium-free pretreatment on AZ91D magnesium alloy

A phosphate-manganese conversion film was proposed as the pretreatment layer between Ni-P coating and AZ91D magnesium alloy substrate, to replace the traditional chromium oxide plus HF pretreatment. The subsequent Ni-P deposited on the layer was also characterized by its structure, morphology, microhardness and corrosion-resistance. The pretreatment layer on the substrate not only reduces the corrosion of magnesium during Ni-P plating process, but also reduces the potential difference between the matrix and the second phase. Thus, a Ni-P coating with fine and dense structure was obtained on the AZ91D magnesium alloy, which shows better corrosion resistance than the Ni-P with chromium oxide plus HF as pretreatment.     

Deposited Chromium as a Corrosion Preventative

Atmospheric corrosion tests of copper plus bright nickel plus microcracked chromium plate have shown that microcracked chromium produced by the post nickel strike method and having a minimum thickness of 0·3/μm provides corrosion resistance at least as good as microcracked chromium produced by other methods, which require a minimum thickness of 0·8 μm in order to ensure an adequate density of microcracking.     

掺杂钨丝电沉积铬的工艺研究

为了研究掺杂钨丝（真空镀铬加热元件）表面电解沉积一定厚度（≥100μm）金属铬的工艺,详细考察了不同温度、电流密度、沉积时间等对镀层的影响,并对镀层进行了性能测试。结果表明,最佳工艺条件为：铬酐150—180μg／L,硫酸1．5～1．8g/L,稀土（La^3＋）添加剂0．5-1．5#L,温度为55℃,电流密度为8～10A／dm^2,电镀时间3h。此工艺条件下所得镀层光亮,色泽好,厚度可达100μm,且镀层耐蚀性好,结合力高。     

高速电弧喷涂FeMnCrAl/Cr3 C2涂层热腐蚀行为

用高速电弧喷涂技术和自行研发的FeMnCrAl/Cr3C2粉芯丝材,在20钢样品表面制备了FeMnCrAl/Cr3C2涂层,采用光学显微镜、场发射扫描电镜、能谱分析和X射线衍射等方法,对FeMnCrAl/Cr3C2涂层的显微组织和热腐蚀行为进行了研究,并与20钢做了对比试验研究.结果表明:FeMnCrAl/Cr3C2涂层主要由固溶相的凝片叠加组成,中间夹杂着氧化物相、未熔颗粒相和孔隙;FeMnCrAl/Cr3C2涂层抗热腐蚀性能明显优于20钢基体,热腐蚀增重约为20钢的1/3-1/4,涂层抗腐蚀性能提高的原因主要是:涂层热腐蚀后表面生成具有保护性的、致密的含Al、Cr氧化物和Cr与Fe的复合氧化物,阻碍了涂层进一步腐蚀.     

高耐蚀缎面装饰性双层镀铬工艺

介绍双层镀铬工艺过程,并讨论影响工艺的主要因素,验证了双层镀铬层的高耐蚀性能。     

三价铬电沉积铬基二元合金工艺的研究进展

近年来,由于六价铬的毒性及其对环境的严重危害,加快了三价铬电沉积的研究。但三价铬电沉积难以获得厚铬镀层,而铬基二元合金在镀厚性方面具有明显的优势。详细总结了三价铬体系电沉积铬镍、铬铁、铬钴、铬磷、铬碳和锌铬等二元合金的工艺,并简述了镀层的特性及应用。三价铬合金电镀将会在生产中有着广阔的应用前景。     

电沉积非晶态铬镀层的组织与性能

用电沉积方法制备了非晶态铬镀层，用X射线衍射仪分析了镀层的相结构，对镀层的组织与性能以及热处理对镀层组织与性能的影响进行了研究。结果表明，非晶态铬镀层的硬度值约为969HV0．025，热处理后由于Cr7C3相的析出使硬度最高可升至1345HV0．025，非晶态铬镀层表现出良好的耐磨性和耐蚀性能，明显优于普通晶态铬镀层。热处理后，镀层与基体的结合力也有明显提高。