锌表面稀土化学钝化及耐蚀性研究

采用三价铈盐对锌进行化学钝化处理 ,研究了有关工艺参数对锌表面稀土转化膜耐蚀性的影响 ,测量了钝化过程中试样的交流阻抗谱 (EIS)和表面显微硬度的变化 ,探讨了稀土转化膜的形成机理 ,并对成膜动力学进行了分析。随着钝化液的铈盐浓度、pH值、温度和处理时间的增加 ,稀土转化膜的耐蚀性也相应提高 ,一定条件下可达到或优于铬酸盐钝化的防蚀性能。稀土钝化成膜反应动力学符合Arrhenius方程 ,反应活化能约为 6 4 8kJ/mol。     

溶解氧对X80管线钢腐蚀行为的影响及其机制

通过交流阻抗技术、动电位极化技术以及X射线衍射仪,研究了溶解氧含量对X80管线钢在库尔勒土壤模拟溶液中电化学行为的影响。结果表明:随着溶解氧含量的不断降低,腐蚀电流密度明显减小,金属腐蚀速率显著下降。这是因为溶解氧含量的不同会导致试样腐蚀产物差异,从而造成了试样在库尔勒土壤模拟溶液中腐蚀速率的变化。当溶解氧含量降到0.35mg/L时,金属电极表面生成了一层以FeCO3为主的腐蚀产物膜,FeCO3明显抑制了腐蚀反应的进行,产物膜对X80钢起到保护作用,此时试样腐蚀现象最不明显。     

钝化膜对方铅矿直接浸出-碳酸化过程的影响

2种浸出方案的对比和X射线衍射分析结果表明，(NH4)2CO3体系中PbS精矿浸出率不超过60％，其主要原因是反应过程中生成了一层PbCO3钝化膜，阻碍了氧气与矿物表面的接触，导致氧化还原反应难以进行。利用电化学测试方法(Tafel曲线、交流阻抗法)研究了方铅矿矿物表面的腐蚀钝化行为，结果表明，PbCO3钝化膜的形成，导致矿物表面电阻增加，反应电流减小，浸出率降低。     

X80管线钢在海滨盐碱土壤模拟溶液中的耐腐蚀性能研究

采用失重法、电化学测试、SEM及XRD微观分析等方法,研究了X80管线钢在海滨盐碱土壤模拟溶液中的耐腐蚀性能。结果表明,在海滨盐碱土壤模拟溶液中,随着浸泡时间的增加,X80钢平均腐蚀速率明显下降,但总的腐蚀程度增加,钢基体表面由以全面腐蚀为主转为以点蚀为主;X80钢的阴极过程为氧的活化控制;腐蚀产物主要由FeOOH(表层)和Fe3O4(内层)组成;X80钢的耐蚀性及腐蚀形态与各试样表面生成的腐蚀产物膜的完整性和致密性有关。研究还发现氯离子含量是影响腐蚀的主导因素。     

黄铜表面富植酸钝化工艺研究

采用植酸(50%,质量分数)8 ml.L-1,双氧水(30%,质量分数)30 ml.L-1,硼酸5 g.L-1,聚乙二醇15 ml.L-1,添加剂4 g.L-1钝化液对冷轧HAl72-2.5-1黄铜带材进行钝化处理,探讨工艺条件(钝化温度、钝化时间和钝化液pH值)对富植酸钝化膜耐蚀性的影响。通过硝酸溶液点滴腐蚀试验对黄铜表面富植酸钝化膜的耐腐蚀性能进行研究。结果表明,富植酸钝化膜的最佳工艺条件为:钝化温度范围是35～40℃,pH值为2.5,钝化时间为60 s。SEM微观形貌显示,膜层表面平整,结构致密。失重试验结果表明:经富植酸处理的试样的平均腐蚀速率为0.0054 g.m-.2h-1,与重铬酸盐处理的试样的平均腐蚀速率(0.0040 g.m-.2h-1)相当,比未经钝化处理的试样的腐蚀速率(0.0376 g.m-2.h-1)低的多,说明采用富植酸钝化处理能对合金材料起到很好的保护作用。经过12 h的盐雾法试验显示:经重铬酸盐处理的试样表面有较多的褐色斑点,表面颜色不均匀,而经过富植酸处理的试样表面为金黄色,只有少量的腐蚀斑,说明采用富植酸处理的试样比采用重铬酸盐处理的试样具有更好的抗变色能力。富植酸钝化液中不含铬,废液中不会产生铬污染。     

稀土碳锰纯净钢表面钝化膜性能研究

探讨了研究稀土碳锰纯净钢表面钝化膜性能的电化学方法,实验表明恒电位极化过程中钝化区的电流和电量可以作为钝化膜性能的表征参量。镧和铈影响碳锰纯净钢的表面钝化能力,改善钝化膜性能的适宜含量大约为镧0.011%、铈0.034%。     

镀锌层表面新型环保钝化膜的耐腐蚀性能

 通过扫描电镜、辉光光谱、电化学测试、盐雾实验及湿热实验等手段探讨了用于钢板镀锌层表面A、B两种新型环保钝化膜的微观状态和耐腐蚀性能。结果表明：A型环保钝化膜的耐腐蚀性能明显优于传统铬酸盐钝化膜;B型环保钝化膜的耐腐蚀性能略低于传统铬酸盐钝化膜;并讨论了A型环保钝化膜耐腐蚀性能优异的原因。     

镀锌和镀铝锌钢材的钝化

据“钢杂志”［俄］１９９８，（２）报道，镀锌和镀铝锌钢材在运输和保管过程中，其表面常常形成白色和黑色的腐蚀产物，恶化了商品外貌，增大了用户加工的难度。为了防止镀锌材受大气腐蚀，一般采用含Ｃｒ溶液钝化，诸如北方钢公司采用ＣｒＯ３进行钝化。可是独联体各国和国外的镀锌机组工作经验证明只使用ＣｒＯ３钝化是不能保证可靠的防蚀和良好的商品外貌。国外钝化一般采用“伊里季特９Ｌ６”使镀层氧化产物稍有酸蚀，保证形成最佳钝化膜。钝化液最佳温度为７０～７５℃，其中Ｃｒ６＋浓度为１０ｇ／ｌ，钝化膜最佳厚度为１５～４０ｍ…     

氧化膜对14Cr12Ni2WMoVNb钢QPQ渗层的室温摩擦磨损和腐蚀性能的影响

为了研究14Cr12Ni2WMoVNb钢QPQ(淬火-抛光-淬火)处理后的氧化膜对渗层室温摩擦磨损和腐蚀性能的影响,利用金相、X射线衍射分析、扫描电镜、能谱分析、划痕仪、摩擦磨损试验机和电化学工作站对试样进行了表征.结果表明:氧化膜对渗层室温摩擦学性能的影响与载荷大小有关.在摩擦时间均为4 min情况下,载荷较小(50 N)时,氧化膜可以降低摩擦系数和体积磨损率;载荷较大(100 N)时,氧化膜被破坏无法降低体积磨损率.氧化膜可明显提高渗层的耐腐蚀性能.含氧化膜试样的极化曲线有明显的钝化区,点蚀电位为-13 mV,去除氧化膜试样在盐雾腐蚀12 h后表面有大范围的腐蚀区域,而含氧化膜试样盐雾腐蚀48 h后才有大区域腐蚀发生.      

高Ta钛合金在沸腾硝酸中的腐蚀行为

对高Ta含量钛合金Ti-32Ta在8 mol/L沸腾硝酸溶液中进行了全浸腐蚀实验,研究了Ti-32Ta合金在沸腾硝酸中的腐蚀行为。采用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线衍射光电子能谱(XPS)等分析方法对钛合金腐蚀表面的钝化膜进行了成分、组织结构及合金价态分析。结果表明:Ti-32Ta合金在沸腾硝酸溶液中呈现均匀腐蚀行为,在介质中通入一定流量的新鲜空气对合金稳定腐蚀阶段的腐蚀速率影响不大。与Ti-6Ta合金相比,Ti-32Ta合金腐蚀后形成的钝化膜更薄更致密,耐蚀性能更好。两种合金腐蚀钝化膜中Ti和Ta的价态组成相同,Ti-32Ta合金腐蚀表面Ta及Ta2O5的含量高于Ti-6Ta合金腐蚀表面。     

Corrosion Protection of Electro-Galvanized Steel by Green Conversion Coatings

A A cerium-based chemical conversion process was studied. First, zinc coating obtained from a free-cyanide alkaline bath, with derivative of imidazol with new brightener, was investigated, zinc-plated steel specimens were treated with a solution of 50 mmol· L^-1 Ce（NO3 ）3 The corrosion behavior of bare and treated mild galvanized steel was evaluated during exposure to 0.5 mol · L^-1 NaCl for different immersion time, using Tafel polarization curves and electrochemical impedance spectroscopy （EIS） measurements. The surface morphology of the coating was studied using scanning electron microscopy （SEM）. The composition and chemical percent of the coating were examined by X-ray dispersion energy （EDAX）. The results of these measurements showed that the newly developed cerium-based conversion coating process was a promising candidate for replacing the conventional chromate treatments used at present for galvanized steel.     

Post treatment of silane and cerium salt as chromate replacers on galvanized steel

A complex film on hot-dip galvanized steel sheet (HDG) was prepared by immersing the sheet in 0.1wt.% Ce(NO3)3 solution and 5vol.% silane solution in turn. The corrosion protection of the complex film was evaluated by potentiodynamic linear polarization(LPR), electrochemical impendence spectra (EIS) and natural salt spray (NSS) tests and compared with that of single cerium film and silane film. The results showed that, the presence of these films on the zinc coating hindered corrosion reaction by reducing the rate of both anodic and cathodic reaction in the corrosion process, and the corrosion protection of the complex film was much better than that of single cerium film or silane film and closed to that of chromate film, because the polarization resistance Rp and electrochemical impendence were increased markedly. Microstructure and chemical composition of these pretreated films were also investigated by scanning electron microscopy (SEM) and AES.     

Formation and characterization of cerium conversion coatings on magnesium alloy

Chemical conversion treatment by rare earth metal salt solution was considered as an alternative to chromium chemical conversion treatment to improve the corrosion resistance of magnesium alloys. In this study, cerium conversion coatings formed on AZ31 magnesium alloy were characterized and the formation mechanism was discussed. X-ray photoelectron spectroscopy （XPS） analysis showed that cerium conversion coating consisted of cerium hydroxides/oxides, in which both tetravalent cerium Ce（Ⅳ） and trivalent cerium Ce（Ⅲ） species co-existed. Cerium conversion coating was a two-layer structure. Atomic force microscopy （AFM） images revealed that the morphology of the inside layer was different from that of the outside one, which was responsible for the inherent adhesive weakness of the coating. Corrosion potential （Ecorr） measurements indicated that poor adhesion limited the improvement of the corrosion resistance of the coating. During the treating process, the increased pH value of the cerium salt solution led to the precipitation of cerium hydroxides/oxides. The formation kinetics of the coating followed a parabolic curve.     

锌镀层表面稀土转化膜成膜机理分析(Ⅰ)

将镀锌层浸泡于以Ce(NO3)3.6H2O为主盐、以30%H2O2为氧化剂的稀土转化膜处理液中,通过计算界面上pH可达到的最大值、Ce-H2O系电位-pH图及Zn-H2O系电位-pH图,推断稀土转化膜可能是由ZnO、CeO2、Ce2O3、Ce(OH)3及Ce(OH)4构成;同时利用X射线光电子能谱仪对该铈盐转化膜表面进行成分分析,结果表明,铈盐转化膜主要是由ZnO、CeO2、Ce2O3、Ce(OH)3、Ce(OH)4构成的复合膜层,这与热力学分析计算相吻合。     

Structure and Corrosion Resistance of a Composite γ-Amino Propyl Triethoxy Silane and γ-Glycidoxy Propyl Trimethoxy Silane Conversion Coating on Galvanized Steel

 In an aqueous solution of the mixtures of γ-amino propyl triethoxy silane and γ-glycidoxy propyl trimethoxy silane, a composite silane conversion coating was developed on galvanized steel. FESEM (field emission scanning electron microscope), XPS (X-ray photoelectron spectroscopy), ATR-FTIR (attenuated total reflection Flourier transform infrared spectroscopy) and SST (salt spray test) were used to characterize the obtained composite silane conversion coating and also the coating formation process was studied. The result showed that the surface of the composite silane conversion coating was complete, consecutive and compact. The coating could endure a neutral salt spray test for 72 h without corrosion. The result of salt spray test indicated that the composite silane conversion coating can provide a better corrosion inhibition than the coating which was composed of the single silane. Based on observation and analysis, it was proposed that the formation process of the silane coating on zinc should consist of three steps: the hydrolysis of the silane molecules, silane chemical adsorption and silane crosslinking condensation. The crosslinking reactions took place between γ-amino propyl triethoxy and γ-glycidoxy propyl trimethoxy silane during the forming process of the coating, and a high crosslinked density interpenetrating structure network was obtained, so the composite silane conversion coating could keep the corrosive substances from the zinc more effectively.     

Improving Corrosion Resistance of Cf/Mg Composites using Rare Earth Conversion Coatings

The surface of carbon fiber reinforced Mg matrix (Cf/Mg) composites was modified by treatment of rare earth conversion coating, and nontoxic, non-pollution Ce conversion coatings were prepared. The effect of the coatings on corrosion behaviors of composites was investigated by electrochemical polarization technology and electrochemical impedance spectroscopy (EIS) in 3.5% NaCl solution. The higher Ecorr and lower icorr were obtained by Ce conversion coatings. EIS results showed that the higher values of R2 were obtained by treatment containing CeCl3, the high corrosion resistance occured in treatment containing CeCl3, the low corrosion resistance in uncoating sample, the coating of treatment containing Ce(NO3)3 was medium. The microstructure of Ce conversion coatings was observed by scanning electron microscopy (SEM), and the elements of corresponding for coatings was characterized by energy dispersive spectrometer (EDS). The micro-cracks and Ce-riched spherical particles were characteristics of these coatings.     

Effects of copper and manganese cations on cerium-based conversion coating on galvanized steel: Corrosion resistance and microstructure characterizations

The cerium conversion coating (CeCC) containing copper and manganese cations was applied to the galvanized steel. The microstructure and the composition of specimen were analyzed by field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). Electrochemical impedance spectroscopy (EIS) and polarization tests were conducted in 3.5 wt% NaCl solution to investigate the coating corrosion resistance. The results show that there are improvements in corrosion resistance and microstructure of CeCC containing copper and manganese cations but copper ions increase corrosion resistance of CeCC from 5800 to 27000 Ω?cm².     

Influence of lanthanum as additive and post-treatment on the corrosion protection properties and surface morphology of mild steel chemically treated by a cerium conversion coating

The influence of cerium conversion coating (CeCC) modified by lanthanum in two forms of additive and post-treatment solution on the corrosion resistance, surface morphology and surface chemistry of the mild steel was studied. Corrosion resistance was evaluated by electrochemical impedance spectroscopy, while the scanning electron microscopy, X-ray photoelectron spectroscopy and contact angle test were employed to investigate the surface characteristics. Results reveal that the CeCC post-treated by lanthanum containing solution gives rise to the deposition of a crack free and uniform conversion coating with enhanced corrosion resistance on the steel surface. Also, the surface free energy is increased after post-treatment.     

Rare earth and silane as chromate replacers for corrosion protection on galvanized steel

The present work aimed at using rare earth lanthanum salt and trimethoxy(viny)silance as chromate substitutes for galvanized steel passivation, in contrast to zinc coating samples treated with chromate. The corrosion resistance was assessed by electrochemical impedance spectroscopy (EIS) and neutral salt spray tests (NSS). Scanning electron microscopy (SEM) was used to characterize the sample surfaces. The organic coating adhesion on the panel was also investigated via varnishes-cross cut tests. The results indicated that rare earth and silane two-step treatment gave more effective anticorrosion performance than Cr, which also provided good paint adhesion. The coating formation mechanism was also discussed.     

Effect of cerium and lanthanum additives on plasma electrolytic oxidation of AZ31 magnesium alloy

Plasma electrolytic oxidation（PEO） coatings on AZ31 magnesium（Mg） alloy were developed using the aqueous solution with alkaline silicate and sodium hydroxide as a base electrolyte system.The effects of cerium（Ce） nitrate and lanthanum（La） nitrate additives on the voltage response,microstructure,compositions and corrosion resistance of PEO coatings were investigated by scanning electron microscopy（SEM）,energy-dispersive spectrum（EDS）,X-ray diffraction（XRD） and potentiodynamic polarization tests,etc.The results showed that Ce and La additives increased the stable voltage and compactness of the PEO coatings,while,those did not change the compositions of the PEO coatings.The corrosion resistance of the PEO coating obtained in solutions with La nitrate of 0.1 g/L was the best,followed by that with Ce nitrate of 0.1 g/L and that without additives.