钼酸盐后处理提高热镀锌上磷化膜耐蚀性的探讨

将磷化后的热镀锌钢板用钼酸盐后处理,以提高磷化膜的耐蚀性。用SEM、EDS、电化学极化测量和盐雾试验研究了钼酸盐后处理对磷化膜组成和耐蚀性的影响。结果表明,经钼酸盐处理后,磷化膜上磷酸锌晶体间的孔隙被钼酸盐膜填补,从而在锌层表面形成了由磷化膜和钼酸盐膜构成的连续完整致密的复合膜;复合膜的极化电阻Rp显著增大,腐蚀电流密度显著减小,耐蚀性大大增强。磷化300s、后处理50s时复合膜的耐蚀性最优,Rp比单磷化膜的增加了一个数量级。     

硅酸钠封闭后处理对磷化热镀锌钢耐蚀性的影响

将热镀锌钢板磷化后再用硅酸钠（水玻璃）溶液封闭后处理,以进一步提高磷化膜的耐蚀性.用SEM、EDS、NSS试验和电化学极化测量研究了硅酸钠封闭后处理对磷化膜组成和耐蚀性的影响.结果表明,经硅酸钠封闭处理后,磷化镀锌钢板表面磷酸锌晶体间的孔隙被含Si、P、Zn的新膜填补,形成了连续完整的复合膜;复合膜的耐蚀性能明显提高,且与硅酸钠溶液的浓度及封闭时间有关;硅酸钠浓度为5 g/L、封闭10 min时形成的复合膜的耐蚀性最佳,NSS试验6个周期（天）后仍不出现腐蚀;试样的阳极极化和阴极极化阻力均显著增强,腐蚀电流密度明显减小,极化电阻增大了一个多数量级.     

添加稀土引致的磷化膜变化与促进机制

用能谱与SEM分析，发现加入稀土硝酸盐(REN)后明显提高了无定形晶体Zn2Fe(PO4)2在磷化膜表面的覆盖率，而使得膜的耐蚀性能提高.此时膜内相关元素含量比例发生了变化：P增大,Zn减小，可见磷对膜耐蚀性的贡献比锌大.讨论认为，稀土硝酸盐是一个有良好载氧能力的催化剂，具有良好的成核促进作用和阴极去极化作用，从而能加速磷化并使膜的耐腐蚀性能提高.      

镁合金AZ31锰系磷化膜的生长过程及形成机理

以磷酸二氢锰的盐溶液为研究体系,采用SEM和EDS和电化学分析手段,研究镁合金AZ31锰系磷化膜的生长过程和形成机理。结果表明:磷化膜的生长过程分为5个阶段:基体溶解-成核阶段(0～130 s)、基体和磷化膜溶解阶段(130～630 s)、磷化膜快速生长阶段(630～1 300 s)、磷化膜稳态生长阶段(1 300～2 000 s)和磷化终止阶段(2 000 s以后)。磷酸盐晶核在镁合金AZ31浸入溶液的初始阶段一次形成,并优先在β相表面经过成核—长大—分裂—细化—增厚5个过程,沿表面方向生长和外延,最终形成致密的磷化膜。并且,磷化膜有两层,第一层是以Mg3(PO4)2和AlPO4以及MnHPO4为主的沉积薄膜;第二层则是在β相表面成核—长大的MnHPO4磷化膜。     

硝酸铈处理对磷化膜组织和耐蚀性的影响

为了发挥磷化膜和铈盐膜的优势,采用硝酸铈前处理或硝酸铈后处理对热镀锌层上的磷化膜进行改进,通过SEM,EDS,NSS和Tafel极化研究了硝酸铈改进磷化膜的显微组织和耐蚀性,并与铬酸盐钝化膜进行了比较。结果表明:硝酸铈前处理或后处理改进磷化膜均为含P,O,Ce和Zn化合物的复合膜,基本上克服了单一膜层的缺陷,使得复合膜的耐蚀性明显增强;硝酸铈后处理改进复合膜的耐蚀性优于铬酸盐钝化膜,有望成为高毒性铬酸盐钝化膜的替代品。     

Mn（NO3）2/Na2MoO4对AZ31B镁合金表面磷化膜微观形貌及耐蚀性的影响

以AZ31B镁合金为基体,通过化学沉积的方法分别在添加Mn(NO3)2,Na2MoO4以及复配的锰系磷化溶液中获得了磷酸盐转化膜。采用扫描电子显微镜(SEM)、电化学工作站及CuSO4点滴等表征手段,研究添加剂对磷化膜表面微观形貌和耐蚀性的影响。结果表明:Mn(NO3)2含量在0~2 g/L之间增加时,磷化膜晶粒尺寸先减小后增大,耐蚀性先增大后降低;Na2MoO4含量在0~0.5 g/L之间增加时,磷化膜晶粒尺寸显著减小,然后增大,耐蚀性显著提高;Mn(NO3)2和Na2MoO4复配后膜层致密,耐蚀性增强,但差于单独引入Na2MoO4的改善效果。综合比较分析,Mn(NO3)2对锰系磷化膜耐蚀性的改善作用较小,而添加0.25 g/L的Na2MoO4获得的膜层更均匀细致,耐蚀性能更佳。     

铝合金表面无铬磷酸盐稀土转化膜的成膜机理及耐蚀性研究

从磷化成膜过程的电化学行为和稀土对磷化膜生长过程的影响两方面,对6061铝合金表面一种不合铬的复合磷酸盐膜的成膜机理进行了研究,并利用极化曲线对其耐蚀性进行了初步探究.结果表明:磷化成膜过程主要分为4个阶段,即基体侵蚀期、晶体初步形成期、基体再溶解和晶体形成期、基体溶解和晶体生长达到平衡期;稀土化合物的引入,提高了磷化...     

热镀锌钢板钝化工艺对耐蚀性的影响

为提高热镀锌钢板的耐蚀性,对热镀锌钢板铬酸盐钝化工艺进行了研究.采用盐雾试验、钝化膜的微观形貌等手段分析了钝化液浓度及钝化工艺参数(钝化液温度、烘干时间、烘干温度等)对热镀锌钢板铬酸盐钝化膜耐蚀性的影响.结果表明,采用试验确定的钝化工艺处理得到的钝化膜耐蚀性明显提高,对实际生产具有较好的指导意义.     

含加速剂的磷化溶液和工艺

为了提高铁、锌和铝等金属及其合金表面的耐蚀性，往往采用含有加速剂的磷化溶液进行磷化处理，以形成耐蚀性的磷酸盐转化膜。磷化溶液中含有的加速剂必须具有良好溶解性，能均匀分布在溶液中，加速剂还必须与溶液中的其它无机化合物和有机化合物相兼容，有利于形成性能优良的磷化膜。本文就含有加速剂的磷酸锌磷化溶液和磷化工艺作一介绍。     

高耐蚀性Zn-Mg合金镀层钢板

由于热镀锌钢板具有良好的耐蚀性 ,在建材行业已广泛地被使用。热镀锌钢板镀锌附着量 90～ 30 0ｇ/ｍ2 。在一般腐蚀环境下年腐蚀速度 5～ 10 ｇ/ｍ2 ,在海岸地带年腐蚀速度 2 0～ 30 ｇ/ｍ2 ,在盐分浓度高的地区热镀锌钢板寿命较短 ,需加以改进。新日铁公司为了满足土木建材行业的需要 ,开发出高耐蚀性Ｚｎ Ｍｇ合金镀层钢板。首先进行模拟锈层试验 ,研究添加Ｍｇ、Ａｌ、Ｎｉ、Ｃｏ等元素在盐水环境下提高耐蚀性状况 :采用0 .1%Ｍｇ耐蚀性有明显提高 ,增加到 0 .5 %Ｍｇ基本上达到饱和状态。综合考虑耐蚀性、操作性和经济效果等规定Ｍｇ含…     

Effect of silicate pretreatment, post-sealing and additives on corrosion resistance of phosphated galvanized steel

Sodium silicate （water glass） pretreatment before phosphating, silicate post-sealing after phosphating and adding silicate to a traditional phosphating solution were respectively carried out to obtain the improved phosphate coatings with high corrosion resistance and coverage on hot-dip galvanized（HDG） steel. The corrosion resistance, morphology and chemical composition of the coatings were investigated using neutral salt spray（NSS） tests, scanning electron microscopy（SEM） and energy dispersive spectroscopy（EDS）. The results show that pretreatment HDG steel with silicate solutions, phosphate coatings with finer crystals and higher coverage are formed and the corrosion resistance is enhanced. Adding silicate to a traditional phosphating solution, the surface morphology of the coatings is nearly unchanged. The corrosion resistance of the coatings is mainly dependent on phosphating time. Phosphating for a longer time （such as 5 min）, the corrosion resistance, increasing with concentration of silicate, is improved significantly. Post-sealing the phosphated HDG steel with silicate solutions, the pores among the zinc phosphate crystals are sealed with the films containing Si, P, O and Zn and the continuous composite coatings are formed. The corrosion resistance of the composite coatings, related to the pH value, contents of hydrated gel of silica and Si2O^2- 5 and post-sealing time, is increased markedly. The improved coatings with optimal corrosion resistance are obtained for phosphating 5 min and post-sealing with 5 g/L silicate solution for 10 min.     

Zinc phosphate conversion coatings on magnesium alloys: A review

Phosphating is one of the most widely used surface treatments of steels and aluminum due to its low-cost, easy mass production, good corrosion resistance and good adhesion with paint. Many researchers have tried to expand applications of the phosphating process, especially to magnesium alloys for automobiles and aerospace applications. Recently, the coatings on magnesium alloys by zinc phosphate conversion coatings (Zn₃(PO₄)₂·4H₂O) have been intensively studied. This paper reviews the state-of-the-art of phosphate conversion coatings developed for magnesium alloys, in terms of coating properties, phosphate conversion coatings processes and compositions of phosphating bath.     

Growth and corrosion resistance of molybdate modified zinc phosphate conversion coatings on hot-dip galvanized steel

The modified zinc phosphate conversion coatings（ZPC） were formed on hot-dip galvanized（HDG） steel when 1.0 g/L sodium molybdate were added in a traditional zinc phosphate solution. The growth performance and corrosion resistance of the modified ZPC were investigated by SEM, open circuit potential（OCP）, mass gain, potentiodynamic polarization and electrochemical impedance spectroscopy（EIS） measurements and compared with those of the traditional ZPC. The results show that if sodium molybdate is added in a traditional zinc phosphate solution, the nucleation of zinc phosphate crystals is increased obviously; zinc phosphate crystals are changed from bulky acicular to fine flake and a more compact ZPC is obtained. Moreover, the mass gain and coverage of the modified ZPC are also boosted. The corrosion resistance of ZPC is increased with an increase in coverage, and thus the corrosion protection ability of the modified ZPC for HDG steel is more outstanding than that of the traditional ZPC.     

稀土硝酸盐促进的铝合金锌系磷化成膜过程

采用扫描电镜(SEM)、X射线衍射(XRD)及能谱(EDX)和电化学测试的方法,研究了稀土硝酸盐(REN)对6061铝合金锌系磷化成膜过程的影响,结果表明,少量的稀土硝酸盐添加到磷化液中可以提高磷化成膜速度和细化晶粒,改变磷化膜的组成,但稀土硝酸盐本身并不构成磷化膜的组成成分,它实质上是具有良好载氧能力的促进剂,具有良好的成核促进作用和阴极去极化作用.与在不含稀土硝酸盐的磷化液中所形成的磷化膜相比,铝合金在含有稀土硝酸盐的磷化液中所形成的磷化膜具有较低的化学活性,其耐蚀性得到提高,在所研究的工艺条件下,最佳硝酸盐含量为20～40 mg/L.     

The growth of zinc phosphate coatings on 6061-Al alloy

Zinc phosphate coating was formed on 6061-Al alloy through a phosphating bath containing mainly ZnO, H₃PO₄, NaF. Yttrium oxide (Y₂O₃) was used as an accelerator of phosphatization to replace nitrite. The morphology, composition and the growth process of the zinc phosphate coating were investigated by SEM, EDX, XRD, FTIR and electrochemical measurements. The phosphate coating formed is composed of hopeite and metallic zinc. The formation and morphology of the zinc phosphate coating were strongly influenced by the presence of yttrium oxide (Y₂O₃) in the phosphating bath. The formed zinc phosphate coatings exhibited high corrosion resistance in 3% NaCl solution as shown by polarization measurement.     

The Effect of The Initiator Heat Treatment Temperature on the Quality of Manganese Phosphate Coatings

The work shows that the quality of phosphate coatings can be substantially improved by raising the heat treatment temperature during the synthesis of the initiator powder. Heat treatment removes water molecules from the hureaulite structure, increases the activity of manganese (II) ions and facilitates their partial substitution by iron (II) ions. The results suggest that ion substitution acts to stabilise the hureaulite initiators during phosphating and enhance the nucleation rate of phosphate crystals.     

Elektrochemische Charakterisierung von Phosphatschichten auf verzinktem Stahl

Electrochemical characterization of phosphate layers on zinc coated steel The electrochemical test for determination of the coverage of phosphated steel [1] is transferred to zinc coated steel. Potentiodynamic current and capacity measurements as well as impedance spectroscopy were used to evaluate the coverage. For electrogalvanized steel the free metal area decreases to 20% within 60 s phosphating time. The layer growth kinetics are determined for different systems by gravimetric measurements. Time dependent measurement of the potential shows a nickel cementation during trication phosphating. The combination of electrochemical methods and XPS-/EDX-measurements shows the incorporation of manganese and nickel from the trication bath into the phosphate layer. Inhibiting passive layers of aluminium and lead were also detected. The influence of iron originating from the alloy layer on galvannealed steel on the phosphating process is examined.     

Zinkphosphat-Überzüge aus übersättigten Bädern

Zinc phosphate coatings from supersaturated baths The author studied the properties of supersaturated phosphating solutions containing zinc phosphate being used for phosphating steel. The study included the influence of the solution variables, and in particular of the ferrous ion concentration, on the supersaturation and the coating properties. The accelerating effect of supersaturation is so strong that heavy, dense, and fine grain coatings are obtained without oxidants and at temperatures as low as + 10° C. Some aspects of the kinetics and the mechanism of coating formation in supersaturated solutions are discussed. Supersaturated phosphating solutions with zinc phosphate may find practical application, particularly where a high degree of protection is desired.     

The mechanism of inhibition by zinc phosphate in an epoxy coating

Epoxy coatings containing different volume fractions of zinc phosphate have been successfully prepared and their inhibitive properties have been studied by electrochemical impedance spectroscopy (EIS) and immersion tests. The results show that zinc phosphate can improve the protection ability of epoxy coatings and its best volume fraction is 30%. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) results indicate that the presence of zinc phosphate can form an inhibiting film which is composed of the phosphating film of FePO₄, Fe₂O₃, and FeO, as well as the shielding film of zinc phosphate on the steel surface.