钢材热浸镀层的腐蚀性能研究及其耐蚀性比较

本文研究了钢材热浸镀锌，热浸镀铝及铝锌合金镀层的耐蚀性能，从服务于生产的实际出发，模拟大气腐蚀和海水腐蚀的情形，对各类类镀层进行了中性和酸性盐雾实验，曝气及浸泡试验，对各类镀层的耐蚀性进行了评定，结合扫描电镜和俄歇电子能谱表面分析技术，探讨了各镀层在不同条件下的腐蚀情形。     

超声热浸稀土铝镀层耐蚀性的优选准则

研究了稀土铝镀层在超声场作用下的表面层厚度变化,通过对不同时间制备的稀土铝镀层的全浸蚀试验分析,提出了超声制备热浸稀土铝镀层耐蚀性的优化准则．     

热浸镀Zn-Al-Si镀层的组织

试验研究了550℃,纯铁在30Al-Zn-1.1Si和40Al-Zn-1.1Si合金浴中热浸镀生成的合金层组织。比较了两种合金镀层在不同浸镀时间合金层生长的变化,发现在τ5C相破裂之前阶段,两种镀层的合金层生长缓慢;随着反应时间延长,熔池扩散的进行,τ5C相破裂,液相开始进入FeAl3相,FeAl3相与τ5C相生长加快,故本试验中对合金层生长起主要抑制作用的是τ5C相;由于富硅的τ1相在界面上富集,再加上Fe2Al5中固溶硅的作用,抑制了铝的扩散,使(Fe2Al5+τ1)相生长缓慢而且致密。通过比较还发现,浸镀相同时间时,随着铝含量降低,合金层的厚度会更薄,τ5C相的抑制作用更强,形成的渣更少。     

Ce元素对低碳钢热浸镀锌镀层耐蚀性的影响

采用热浸镀法在低碳钢表面制备含Ce元素的镀锌层,利用光学显微镜(OM)、扫描电镜(SEM)、X射线衍射仪(XRD)、中性盐雾试验(NSS)以及电化学测试方法,揭示不同Ce元素添加量对镀层微观组织结构及耐蚀性能的影响规律。结果表明:在镀液中添加适量的Ce元素可在细化镀锌层晶粒和减薄镀锌层厚度的同时有效地提高镀锌层的耐蚀性。与纯锌镀层相比,镀液中添加0.012%和0.2%Ce(质量分数)后镀层的腐蚀速率分别降低24%和27%。Ce元素提高镀锌层耐蚀性的机理为:一方面,Ce的添加提高了腐蚀产物中Zn₅(OH)₈Cl₂?H₂O占比,从而提高了腐蚀产物的致密性与粘附性;另一方面,腐蚀过程所形成的Ce(OH)₃沉淀吸附在阴极相,阻碍氧的扩散,抑制了阴极吸氧反应。当镀液中添加超过0.012%Ce后(过饱和),阴极反应已被充分抑制,因而继续提高Ce添加量对镀锌层耐蚀性的提高有限。     

硅含量对热浸镀Zn-20%Al镀层组织和耐蚀性的影响

将Q235钢置于不同硅含量的Zn-20%Al熔池中浸镀不同时间,并将浸镀样品置于中性盐雾腐蚀试验箱中腐蚀,利用扫描电镜、能谱分析仪和X射线衍射仪观察镀层的组织结构和腐蚀产物,研究了硅含量对热浸镀Zn-20%Al镀层组织及耐腐蚀性的影响。结果表明:随着熔池中硅元素的增加,合金层中周期性层状组织逐渐消失;添加少量的硅就可以强烈抑制铁铝之间的反应,减薄镀层的厚度;当硅含量增加到0.8%时,中间合金层由Fe Al_3相向Fe-Al-Si三元化合物τ_4相转变;硅的加入可以使腐蚀环境下的镀层表面形成一层致密的化合物Al_(3.21)Si_(0.47),较大程度地隔绝腐蚀环境,提高镀层耐腐蚀性。     

表面粗糙度对热浸镀锌镀层特征及耐蚀性的影响

为提升热浸镀锌钢板的表面质量,将热镀锌钢板进行连续热浸镀锌试验生产,采用场发射扫描电镜、显微镜和盐雾实验等手段,对生产试验的镀锌板进行相关的实验分析,研究了热浸镀锌基板表面粗糙度对含Sb和Pb的热浸镀镀锌板锌花尺寸均匀性和镀层厚度及物相组成特征的影响,以及锌花大小与耐腐蚀性的关系。结果表明:基板表面粗糙度越大,锌花尺寸越小且镀层厚度也小,δ相层中Fe元素含量较大,耐腐蚀性能较好。     

Mn、Ti对热浸镀Zn-5Al合金镀层组织与耐蚀性的影响

采用扫描电镜(SEM),能谱仪(EDS)、电化学测试等手段研究了Mn、Ti对热浸镀Zn-5Al合金镀层组织与耐蚀性的影响。结果表明:Zn-5Al-0.2Mn和Zn-5Al-0.15Ti合金镀层的腐蚀速率分别为Zn-5Al合金镀层的44.8%和39%;在Zn-5Al合金镀层中添加Mn、Ti,促进了Al在过渡区的集聚,使含Fe2Al5过渡层的厚度增大;添加Mn使Zn-5Al合金镀层中的共晶组织细化,而添加Ti则使共晶组织粗化,但此时共晶Al相已与钢基体连续融合;Zn-5Al-0.2Mn和Zn-5Al-0.15Ti合金镀层的自腐蚀电流密度均比Zn-5Al合金镀层的小,具有更好的耐蚀性。     

钢的热浸铝镀层

前言可以通过电镀金属层,也可以防护薄膜来防止钢铁表面环境腐蚀。成形的例子有镀锌和镀铝,后来又出现了镀铅和锡。在镀于钢上的有色金属中,锌是最便宜的,此外,人们认为铝镀层的发展很可能与电镀层相比。锌铝合金镀层在用于钢上时具有三种防护性能:(1)致密表层隔离了底层金属与外界环境的接触;(2)如果镀层受到机械损伤,则它保护暴露的金属使它变为阴极,例如,在海洋环境中。(3)形成良好的氧化膜,可以起到防护作用。     

热浸Zn-Al-Mg合金镀层的显微组织和摩擦性能

用光学显微镜、维氏硬度计和摩擦磨损试验机对Zn-2Al-x Mg(x=0、0.5、1.0、1.5,质量分数,%)合金镀层的显微组织、硬度和摩擦性能进行了观察分析。结果表明,随Mg含量增加,合金镀层晶粒细化,硬度提高。在相同载荷下,随Mg含量增加,4种合金镀层的摩擦因数相近,耐磨时间先增加后减小,其中含1%Mg的合金镀层耐磨时间最长。Zn-2Al-1Mg合金镀层的耐磨性优于Zn-2Al合金镀层。     

Effects of rare earth metal addition on surface morphology and corrosion resistance of hot-dipped zinc coatings

Effects of rare earth metals (REM) addition on surface morphology and corrosion resistance of hot-dip galvanised steel were investigated. The corrosion resistance of steel samples galvanised with zinc and zinc alloys containing 0.05, 0.1, 0.2 and 0.5 wt.% REM were evaluated by various corrosion tests such as weight loss in salt spray chamber and natural sea water, sacrificial protection ability in contact with fog in salt spray chamber and after immersion in sea water, potential-time in sea water and linear polarisation in sodium chloride solution. Surface morphology and nature of the corrosion products were also investigated. The results indicated that the addition of small amounts of REM to the molten zinc galvanising bath can improve the corrosion resistance of hot-dip galvanised steel. Mechanisms by which the corrosion resistance of hot-dip galvanised steel are improved in presence of REM have been discussed.     

Electrodeposition and corrosion resistance of Ni-W-B coatings

A ternary nickel-base alloy Ni-W-B has been developed for surface corrosion and wear resistance to replace chromium plating, which uses environmentally hazardous solutions. The deposition conditions used an alkaline bath and insoluble anodes. The as-deposited alloy typically contains 40 wt % W and 1 wt % B and has an amorphous or partially amorphous structure. These deposits compare favorably with hexavalent chromium deposits in throwing power, color uniformity, and reflectivity. The corrosion resistance of Ni-W-B alloy was compared with hexavalent chromium and electroless nickel deposits in a variety of acids, including hydrochloric, sulfuric, fluoroboric, and phosphoric. In all cases, best results were obtained with the Ni-W-B deposits.     

Microstructure and corrosion resistance of the brazed WC composite coatings in aerated acidic chloride media

The paper presents the corrosion behavior of the brazed WC composite coatings by using a combination of weight loss method and electrochemical polarization measurement. The brazed WC composite coatings have lower corrosion current densities compared with the 316L stainless steel and show a superior corrosion-resistance property. A further decrease of corrosion current densities is observed for the brazed WC composite coatings with the extending of etching time. The X-ray diffusion (XRD) analysis shows that WC, γ-Ni solid solution and γ-Ni + Ni₃B eutectic solution were presented in the coating surface. The surface morphology observation and composition analysis were conducted by scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy. The insoluble oxidation products were deposited on the corroded coating surface.     

Microstructure and corrosion resistance of molybdenum and aluminum coatings thermally sprayed on 7075-T6 aluminum alloy

Pitting corrosion upon 7075-T6 high strength aluminum alloy, often associated with cathodic intermetallic particles decreases its fatigue life by a factor of about 6 to 8. In order to improve the corrosion resistance of this alloy, arc spray coatings of molybdenum and aluminum are applied. The open circuit potential and potentiodynamic polarization measurements made in 3.5% NaCl naturally aerated solution reveal that the molybdenum coating, which has an excellent hardness, shifts the 7075-T6 corrosion potential (E _corr) to noble values and increases slightly the corrosion current density (i _corr). On the contrary, when the aluminum coating alloy is applied, both E _corr and i _corr are shifted to better values. The increase of i _corr of the alloy when molybdenum coating is applied can be attributed to the high porosity present into the coating. On the other hand, microstructure observations of the aluminum coating reveal a small porosity, which helps the formation of passive oxide film that protects the coating against a further corrosion.     

NiCrWFeSiBCCo合金涂层的组织与耐空蚀性

采用超音速火焰喷涂技术,在1Cr18Ni9Ti不锈钢基体表面制备NiCrWFeSiBCCo合金涂层. 采用金相显微镜(OM)、超景深体视显微镜(SM)、扫描电镜(SEM)观察涂层的显微组织和空蚀前后表面的微观形貌;采用表面粗糙度测试仪和显微硬度测试仪对涂层表面粗糙度和显微硬度进行表征;采用X-Ray衍射仪(XRD)分析涂层的相组成;采用磁致伸缩空蚀试验仪测定涂层的空蚀性能,并与1Cr18Ni9Ti不锈钢的空蚀性能进行比较. 结果表明,采用超音速火焰喷涂(HVOF)制备的NiCrWFeSiBCCo涂层组织均匀,结构致密(平均孔隙率为0.63%),硬度为1 004 HV,NiCrWFeSiBCCo涂层的抗空蚀性能明显优于1Cr18Ni9Ti不锈钢.     

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。     

XPS characterization and corrosion resistance of cerium-treated magnesium coatings

Cerium conversion treatment was applied on magnesium coatings in a solution containing CeCl3.The composition of the cerium conversion layer on magnesium was investigated using X-ray photoelectron spectroscopy(XPS).It was revealed that the composition predominately consisted of a three-valent state cerium compound with a relative abundance around 90%.Some of Ce3+ was oxidized to Ce4+.Electrochemical impedance spectroscopy results revealed that the total impedance of cerium-treated samples increased for a sho...     

Deposition and corrosion resistance of electroless Ni-PCTFE-P nanocomposite coatings

The present work deals with the process of electroless deposition and electrochemical corrosion behavior of nickel-polychlorotrifluoroethylene-phosphorous (Ni-PCTFE-P) nanocomposite coatings. The process of autocatalytic-catalytic reduction of Ni in nickel sulfate and sodium hypophosphate solution with PCTFE suspended particles has been employed for the formation of the electroless Ni-PCTFE-P composite coatings. Surface morphology and composition of the composite coatings are characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) measurements and X-ray diffraction (XRD) analysis. Corrosion behavior of coatings is evaluated using open-circuit potential (E_OCP) measurements, electrochemical impedance spectroscopy (EIS) and polarization techniques in 3.5 wt.% NaCl solution. The study reveals significant shift in corrosion potential towards the noble direction, decrease in corrosion current density, increase in charge transfer resistance and decrease in double‐layer capacitance values with the incorporation of PCTFE particles in the Ni-P matrix. The significant improvement in corrosion resistance observed for Ni-PCTFE-P nanocomposite coatings (25.3 kΩ cm²) compared to Ni-P (16 kΩ cm²) could have resulted from the microstructural differences of pure Ni-P with Ni-PCTFE-P nanocomposite coatings.     

The corrosion resistance of electrodeposited zinc-nickel alloy coatings

The corrosion behaviour of electrodeposited zinc-nickel (Zn-Ni) alloy coatings has been studied in aqueous chloride environments. The corrosion rates of detached zinc alloys containing up to 25% Ni by weight were determined using linear polarisation techniques. The corrosion rate of Zn-Ni alloys was found to decrease with increasing Ni content over the compositional range studied. Galvanic corrosion measurements have indicated, however, that Zn-Ni alloy coatings become less sacrificial toward steel as the Ni content is increased. These results are used to interpret the corrosion behaviour of electroplated steel in a neutral salt fog environment.