电镀防护性锌基合金镀层钝化膜的耐蚀性

防护性锌基合金镀层钝化膜的耐蚀性比锌镀层钝化膜提高２－４倍。ＸＰＳ及ＡＥＳ分析表明,合金镀层钝化膜与锌镀层钝化膜均由ＣｒＯ３、Ｃｒ２Ｏ３、Ｚｎ（ＯＨ）２、ＺｎＯ及Ｈ２Ｏ等组成,并且ＣｒＯ３／Ｃｒ２Ｏ３的相对含量和Ｚｎ（ＯＨ）２／ＺｎＯ相对含量也基本相同,它们的区别在于,合金镀层钝化膜中总铬量较高,膜层完整、致密,镀层／钝化膜界面存在铁系金属的富集层,这是锌基合金镀层钝化膜具有高耐蚀性的主要原因。     

电沉积Zn—Ni合金的耐蚀性研究

在含锌的合金电镀中,已报道的有Zn—Ni,Zn-Sn,Zn-Fe,Zn-Co和Zn-Cd.其中以Zn-Ni和Zn-Fe合金电镀被认为最有发展前途.关于Zn-Ni合金镀层优异耐蚀性的认识源于这样一个实验:四十年代美国宾西法尼亚3S公司(Standerd Steel Spring)在钢铁上先镀一层4μm Ni,后镀一层同样厚度的锌,然后在370℃以下热扩散30到120分钟,得到具有4种晶相的Zn-Ni合金.其腐蚀试验表明,8μm的Zn-Ni合金经盐雾试验1536小时,表面只有2%区域出现腐蚀,同样厚度的Zn镀层,试验1000小时,有25%出现锈蚀.经大气腐蚀试验16个月,这种合金无任何腐蚀,而5μm厚的镍镀层大气试验1个月有25%出现锈蚀.但这种工艺并未获得推广,因为大多数电镀车间并不配备这样的加热炉.然而,Zn-Ni合金所具有的优异防腐蚀性能却大大的推动了人们直接从水溶液中获得Zn-Ni合金的研究.文献[3]介绍了已发表的各种配方与工艺,但其中最关键的光亮剂都以“添加剂”二个字给保密起来了.事实上没有光亮剂的Zn-Ni合金镀层是十分粗糙的,其防护能力不算高.Zn-Ni合金镀层在国内大规模的应用尚不多.在日本,1984年住友金属工业公司,有两条Zn-Ni合金电镀生产线,年产44.4万吨Zn-Ni合金钢板.     

锌镍合金镀层耐蚀性的探讨

根据腐蚀电化学基本原理，探讨了锌镍合金镀层的耐蚀机理，测试了不同成分的锌镍合金镀层的腐蚀电位和极化曲线并进行了分析。     

低镍含量碱性电镀锌镍合金工艺研究

电镀锌镍合金以其优异的耐蚀性能于八十年代投入生产用作钢铁材料的耐蚀保护镀层,特别是在汽车工业中得到广泛应用.锌镍合金电镀液有弱酸性和碱性两种体系,其中碱性体系具有较好的分散能力,镀液腐蚀性弱,废水处理方便,生产成本低等优点,近年来得到迅速发展.碱性电镀锌镍合金中的镍含量大多在5～10Wt%的范围内.本文研究了在碱性体系下的镍含量小于1Wt%的电镀锌镍合金工艺,并获得了光亮的耐蚀性好的锌镍合金镀层.     

激光溶凝对铝硅合金和锌基合金耐蚀性的影响

铝硅合金和锌基合金具有良好的工艺性能.用CO_2激光器照射金属表面进行激光表面熔凝处理.可在合金表面形成具有耐蚀性的表面层,从而使合金的应用范围扩展.     

非晶态铁基合金电镀工艺

铁基非晶态合金是非晶态合金中重要的一类,近十多年来有许多研究成果。本文总结了主要的铁基非晶态合金电镀工艺及镀层性能,也提出了存在的问题。     

EN Ni—P镀层耐蚀性探讨

本所通过生产实践和实践证明化学Ｎｉ－Ｐ镀层耐蚀性不仅取决于镀层的磷含量，而且与镀层的组织结构，成分均匀性，表面形貌，热处理温度以及镀液的组成，操作条件，预处理的质量有关。     

稀土铈对于碱性电镀锌层耐蚀性的影响

研究了稀土元素铈在碱性镀锌中的应用。试验研究了不同工艺条件的含铈镀层，优化了工艺条件；检测了当镀液中含有铈元素时，镀层耐蚀性的变化情况；利用电子探针及X射线衍射分析了含铈的试样，测定了铈进入镀层的含量，剖析了铈存在的作用及其对镀层的耐蚀性影响的原因。     

Characterization of calcium-modified zinc phosphate conversion coatings and their influences on corrosion resistance of AZ31 alloy

Two kinds of phosphate conversion coatings, including zinc phosphate coating and zinc-calcium phosphate coating, were prepared on the surface of AZ31 alloy in phosphate baths. The morphologies of these coatings were observed using scanning electron microscopy. Their chemical compositions and structures were characterized using energy-dispersive X-ray spectrum, X-ray photoelectron spectroscopy and X-ray diffraction. The corrosion resistance of the coatings was evaluated by potentiodynamic polarization technique. The results show that the flowerlike Zn-Ca phosphate conversion coatings are mainly composed of hopeite (Zn₃(PO₄)₂·4H₂O). They have a quite different morphology from the dry-riverbed-like Zn phosphate coatings that consist of MgO, MgF₂, Zn or ZnO and hopeite. Both of the zinc and zinc-calcium phosphate coatings can remarkably reduce the corrosion current density of the substrates. The Zn-Ca coating exhibits better corrosion resistance than the Zn coating. Introduction of calcium into the phosphate baths leads to the full crystallinity of the Zn-Ca coating.     

Synthesis and evaluation of corrosion resistance of molybdate-based conversion coatings on electroplated zinc

Three molybdate-based conversion coatings on electroplated zinc have been prepared and the composition, morphology, and structure of these coatings are measured by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. It was found that these coatings with ‘meshwork’ surface were complex coatings composed of multiple compounds. Molybdenum species were present in the conversion coating as Mo (VI) and Mo (IV) compounds. The results of neutral salt spray test showed that molybdate-based conversion coatings with the addition of H₃PO₄, SiO₂ and TiOSO₄ in the passivation baths possess higher corrosion resistance compared with chromate conversion coatings, which was due to the compactness and anti-corrosion essence of the conversion coating.     

New Fe-based soft magnetic amorphous alloys with high saturation magnetization and good corrosion resistance for dust core application

Fe-rich amorphous dust core alloys with minor-addition of Mo and/or Cr were synthesized because of the industrial request of mass production of high efficient low core loss Fe-based dust cores. It was found that the present Fe-(Cr, Mo)-P-B-Si-(C) amorphous alloy ribbons exhibit good soft magnetic properties of above 1.5 T for saturation magnetization, below 10 A/m for coercivity and rather good corrosion resistance in 3%NaCl aqueous solution. Besides, the amorphous alloy ribbons exhibit good bending ductility in as-spun and optimally annealed states. It is noticed that these characteristics are much superior to those for commercial Fe-Cr-Nb-P-B-Si soft magnetic dust core alloy (SENNTIX). In addition, the annealing treatment was noticed to cause the improvement of corrosion resistance without detriment to bending ductility. The new Fe-based soft magnetic alloys with good combined characteristics are expected to be used as the basic material as high-efficient soft magnetic dust cores in a high frequency range.     

Phosphate coating on stainless steel prepared in electrolyte with silica sol: zinc segregation,post-treatment and corrosion resistance

Phosphate film is generally not compact, left with microscopic cracks or pores during the phosphating process. Silica sol is incorporated into the phosphating solution to fabricate phosphate films on stainless steel 316L by electrochemical method. It is found that at appropriate amount of silica sol (8 vol.-%), the cracks on the hopeite film are effectively filled, while they appear again when much more silica sol is added as observed by SEM images. Moreover, zinc is found simultaneously formed as detected by the energy dispersive spectroscopy and X-ray diffraction measurements. In order to improve the performances of the hopeite film, we use titania sol by dip coating to cover the hopeite film. The titania sol can improve the anticorrosion ability of the films with limited extent since its crack formation during curing. By adding polyvinyl butyral (2 wt-%) in this sol, the composite film exhibits great improvement in corrosion resistance resulting from the cracks remedy and synergy effect of zinc with titania gel.     

Influence of alloying elements on the corrosion resistance of rolled zinc sheet

The influence of alloying elements on the corrosion behaviour of rolled zinc sheet in aqueous media has been investigated by means of electrochemical techniques. All the changes in corrosion behaviour seen in this study could be attributed to modification of the formation or the stability of the passivating oxide film on the zinc surface. A low concentration of copper (0.6 wt.%) inhibited the formation of the passivating film and reduced the stability of the film. Conversely, a low concentration of chromium (0.5 wt.%) accelerated the passivation process and raised the stability of the film. The passivation and corrosion behaviour shown by a commercially produced ternary alloy containing copper and titanium additions was almost the same as the behaviour shown by a model binary alloy containing only copper. All the results obtained in this study were consistent with the hypothesis that alloying elements alter the electron-conducting and/or ion-conducting properties of the passivating oxide film.     

Development of zinc oxide-rich inner layers in hot-dip zinc coating for barrier protection

The formation of ZnO composite-rich inner layers and its impact on the galvanization process and characteristics of hot-dip zinc coating were explored in the present study. Steel substrates were initially coated with a fragmented layer of ZnO and then subsequently galvanized. The presence of ZnO-rich inner layer influenced the galvanizing process substantially. The process resulted in the formation of more adherent layers with lower coating thickness. The presence of the inner oxide layer caused a modification of the inner alloy structure and the coating composition. The physical, mechanical as well as galvanic performance of the coating were also improved by the presence of the ZnO-rich inner alloy layers.     

Passive films and corrosion resistance of Ti–Hf alloys in 5% HCl solution

Ti–Hf alloys with Hf contents of 10, 20, 30, and 40 mass% were prepared by a tri-arc furnace and homogenized at 1273 K for 21.6 ks, and then these alloys were cold rolled into 3-mm-thick plates. The alloy specimens were subjected to a solution treatment in a vacuum at 1223 K for 3.6 ks and then rapidly quenched in ice water before corrosion tests. The corrosion resistance of these alloys was investigated by studying the anodic polarization curves at 310 K in 5% HCl solution to determine the potential use of these alloys in biomedical applications. The passive films formed on the surfaces of the alloys were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The results reveal that all the Ti–Hf alloys exhibit a passive behavior in 5% HCl solution, which is attributed to the passive film formation of a mixture of both HfO₂ and TiO₂. The corrosion resistance of the Ti–Hf alloys gently increases with the Hf content and the Ti–Hf alloys exhibit better corrosion resistance than commercial pure (CP) Ti—the currently-used metallic biomaterial.     

Electroless Ni-Sn-P coating on AZ91D magnesium alloy and its corrosion resistance

An electroless Ni-Sn-P coating was deposited on AZ91D magnesium alloy in an alkaline-citrate-based bath where nickel sulphate and sodium stannate were used as metal ion sources and sodium hypophosphite was used as a reducing agent. The phase structure of the coating was amorphous. SEM and attached EDS observation revealed the presence of dense and uniform nodules in the ternary coating and the content of tin was 2.48wt.%. Both the electrochemical analysis and the immersion test in 10% HCl solution proved that the ternary Ni-Sn-P coating exhibited better corrosion resistance than the Ni-P coating in protecting the magnesium alloy substrate.     

The effects of niobium and nickel on the corrosion resistance of the zinc phosphate layers

In this investigation the viability of nickel substitution by niobium in zinc phosphate (PZn) baths has been studied. Samples of carbon steel (SAE 1010) were phosphated in two baths, one containing nickel (PZn + Ni) and the other with niobium substituting nickel (PZn + Nb). Potentiodynamic polarization curves (anodic and cathodic, separately) and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion resistance of the phosphated carbon steels in a 0.5 mol L^− 1 NaCl electrolyte. The phosphate layers obtained were analysed by X-ray diffraction and it was found that they are composed of Zn₃(PO₄)₂.4H₂O (hopeite) and Zn₂Fe(PO₄)₂.4H₂O (phosphophylite). Surface observation by scanning electron microscopy (SEM) showed that the PZn + Ni layer is deposited as needle-like crystals, whereas the PZn + Nb layer shows a granular morphology. The electrochemical results showed that the PZn + Nb coating was more effective in the corrosion protection of the carbon steel substrate than the PZn + Ni layer. The results also suggested that nickel can be replaced by niobium in zinc phosphate baths with advantageous corrosion properties of the layer formed.     

可降解医用镁合金耐腐蚀性能研究进展

本文针对可降解吸收的医用镁合金的耐腐蚀性较差、在临床上的应用受到了很大的限制的问题,介绍了3种典型医用镁合金耐腐蚀性能的变化和近几年有关可降解医用镁合金的腐蚀研究进展,总结了研究可降解医用镁合金耐腐蚀性能的实验方法和结果.结论 是未来医用镁合金既要充分发挥其可降解吸收的优点,又要把控好在人体服役期间的降解速度.