新型铝合金Ce-Mo基转化膜

研制了一种新型的铝合金Ce-Mo基转化膜工艺－AM工艺,此种工艺的成膜溶液组成为：（NH4）2Ce(NO3)62.5g/L,NaKC4H4O6.4H2O2.5g/L,Na2co37.5g/L,NaMoO45.0g/L.铝合金浸在浸腾的此种成膜溶液中20min,可形成约3.6um厚的铝合金Ce-Mo基转化膜,于5％NaCl溶液中进行了极化曲线测试和浸泡试验表明,对LF6铝合金,经AM工艺处理形成的转化膜抗局部腐蚀能力超过了传统的铝吕金铬酸盐转化膜,但对LC4铝合金,此种转化 耐蚀性能不理想,EDAX和SEM分析表明,LF6和LC4两种铝合金上莆成的AM转化膜主要由Al,Ce,Mo的氧化物或氢氧化物组成,但们的表面形貌差异很大。     

2024铝合金氟铝酸盐转化膜的制备及其防腐蚀性能

为了寻找替代传统铬酸盐转化的处理工艺,采用由NaF,(NH4)2SiF6,(NaPO3)6和钛盐促进剂组成的转化液,在2024铝合金表面制备了一种氟铝酸盐化学转化膜,优化了转化液组分及转化工艺条件。结果表明:最优工艺为5.0 g/L NaF,5.0 g/L(NH4)2SiF6,0.9 g/L(NaPO3)6,0.5 g/L钛盐促进剂,pH值为4.7,室温,20 min;最优工艺所得氟铝酸盐转化膜由排列紧密且形状规则的晶体颗粒组成,表面覆盖有胶状物,膜层连续而致密、呈亚光,组成(质量分数)为7.53%O,48.87%F,19.11%Na,20.78%Al,0.79%Si,1.66%P,1.26%Cu;氟铝酸盐转化膜耐蚀性优良,最优工艺所得转化膜耐盐雾腐蚀达285 h,其使铝合金在3.5%NaCl溶液中的腐蚀电位增加了58 mV,腐蚀电流密度降为钝化前的1/9。     

镁合金化学转化膜的耐腐蚀性研究

在50g/L KMnO4和100g/L Na3PO4组成的基础化学转化溶液中添加6 g/L缓蚀剂,在AZ31镁合金上获得了化学转化膜.用植酸作为转化处理液,分析了pH值、温度、转化时间及植酸用量(质量分数)对AZ31合金成膜及耐蚀性的影响,SEM观察表明,植酸膜经3.5%的NaCl溶液浸蚀后有一定的自愈合能力.这两种方法获得的转化膜均比铬酸膜光滑、致密均匀.     

2A96铝合金表面含三价铬转化膜制备 及其电化学性能研究

通过调整Cr_2(SO_4)_3浓度和K_2ZrF_6浓度,在2A96铝合金表面制备了含三价铬转化膜;采用极化曲线和交流阻抗谱研究了所制备含三价铬转化膜的电化学性能,利用金相显微镜和扫描电镜(SEM)对铝合金成膜前后的表面形貌进行观察和分析。结果表明,在单因素试验中,质量浓度分别为5 g/L Cr_2(SO_4)_3和2.0 g/L K_2ZrF_6溶液中制备含三价铬转化膜的自腐蚀电位最大,交流阻抗谱的相位角最大,阻抗弧长也最大,耐腐蚀性能最好;显微形貌分析得出成膜后的2A96铝合金表面覆盖了一层转化膜。     

6063铝合金Zr-Ni黑色化学转化膜的制备及表征

以K2ZrF6为主要成膜原料,Ni2SO4·6H2O为着色剂,实现在常温下对6063铝合金的无铬化学转化处理,处理液无需另外添加氧化剂而性能稳定,数分钟内快速成膜。通过添加Ni元素使转化膜由灰色变为黑色,解决了锆转化膜的着色问题。通过SEM观测、XRD分析及电化学测试,发现Zr-Ni转化膜宏观上均匀,表面微观形貌呈短屑状结构;转化膜由ZrO0.44F3.12、AlNi、Zr(F,O)3.6、NiZrF6、KAlF4、Al及AlF3组成;该转化膜具有良好的耐腐蚀性能,膜层结构电路为C1/R1/(L2+R2)/(L3+R3)。     

稀土转化膜钼酸盐后处理工艺研究

开发出一种耐蚀性优良的铝合金表面富铈稀土转化膜化学成膜工艺,研究了通过钼酸盐溶液处理进一步提高转化膜耐蚀性能的后处理工艺,具体工艺参数为:10g/L钼酸钠,温度50℃,时间30 min;通过电化学测试、中性盐雾试验和EDS能谱分析对转化工艺及后处理工艺进行了表征.结果表明,该工艺能够有效地提高转化膜的耐蚀性能,转化膜耐中性盐雾试验时间可达到500h.这可能是由铈盐在水溶液中的"自封闭"特征和钼酸盐的缓蚀性共同作用所致.     

工艺参数对铝合金稀土转化膜微观形貌的影响研究

采用稀土盐Ce（NO3）3与氧化剂KMnO4作为无铬化学转化液的主要成分，在6063铝合金表面制备了耐腐蚀稀土转化膜，利用正交试验法与单因素实验法对转化膜处理溶液浓度、溶液温度与pH值以及时间等工艺参数进行了优化，利用SEM微观分析法，并对稀土转化膜的表面形貌进行了研究，并分析了处理工艺参数对转化膜微现形貌与耐腐蚀性能的影响。     

环保型铝及铝合金表面化学转化工艺及性能研究

开发了一种由无毒的钛盐、锆盐和有机聚合物组成的铝及铝合金化学转化剂CF-5,以取代有毒的六价铬钝化.其配方为:0.10～2.00g/L PO43-,0.05～1.00g/L Ti4 ,0.05～1.50g/L Zr4 ,0.30～1.50g/L F-,0.50～2.00g/L氧化剂,0.05～3.00g/L有机聚合物(水溶性环氧聚合物或丙烯酸聚合物).该钝化剂可在铝及铝合金表面形成性能优良的化学转化膜,膜层有较好的耐蚀性能,且与有机涂层具有良好的附着力.     

5052铝合金Ti-Ce转化膜的性能

为了消除铬酸盐处理六价铬的危害,室温下在5052铝合金表面制备了环保型Ti-Ce转化膜。通过正交试验确定了转化液的最佳组成:1.0 g/L Ce(NO3)3.6H2O,4.0 g/L NaF,4.0 g/L Ti(SO4)2,1.5 g/L H2O2,2.0 g/L EDTA;同时采用单因素法研究了转化液pH值对转化膜厚度的影响,采用中性盐雾试验考察了转化膜的耐蚀性,并通过扫描电子显微镜和能谱仪分析了转化膜的微观形貌和成分。结果表明:Ti-Ce转化膜通过了96 h的中性盐雾测试;转化膜均匀且缝隙较少,主要含有C,O,F,Al,Ti,Ce等元素,不含有害物。     

AZ91D镁合金钒酸盐转化膜的最佳制备工艺

过去,对镁合金钒酸盐无铬转化工艺的研究较少.通过正交试验和单因素试验优选了以NH4VO3为主盐的镁合金钒酸盐转化工艺.结果发现,在5 g/L NH4VO3,30 g/L H2PO2-,30 g/L NH4NO3,60 ℃条件下成膜15min可以在AZ91D镁合金表面形成均匀、完整的灰色转化膜;该膜层的微观形貌与铬酸盐转...     

铝合金表面铈锰化学转化

以硝酸铈和高锰酸钾为主盐,在6063铝合金表面制备了Ce-Mn化学转化膜。研究了室温下成膜时间、转化液pH值、硝酸铈和高锰酸钾浓度对Ce—Mn转化膜电化学性能的影响,获得了最佳成膜工艺：7g／LCe（NO3）3,2g／LKMnO4,时间9min,pH值2．3。采用极化曲线考察了所得转化膜的耐蚀性,并通过扫描电镜和能谱仪分析了膜的表面微观形貌和组成。结果表明：Ce．Mn转化膜比6063铝合金具有更低的腐蚀电流密度和更大的极化电阻,表现出良好的耐腐蚀性能;Ce-Mn转化膜主要成分是铝、镁、铈、锰和氧。     

成膜时间对镁合金表面Ce-Mn转化膜组织及耐蚀性的影响

以四硼酸钠为添加剂,Ce(NO3)3-KMnO4为主要成膜剂,室温下在AZ91镁合金表面制备了Ce-Mn转化膜。基于优化的成膜剂浓度比,主要研究了成膜时间对膜层组织和耐蚀性的影响。结果表明转化膜层主要由O、Mg、Al、Mn、Ce等元素组成,随成膜时间延长,膜层不断增厚,且产生裂纹甚至膜层剥落。Ce(NO3)3/KMnO4浓度比较低时成膜速率较慢,膜层中Ce/Mn原子较小,但膜层的电化学性能较优。开路电位随成膜时间延长呈现先急剧增大,后缓慢增加并在2min后趋于平稳的趋势。室温下处理2min即可获得组织致密且耐腐蚀性能较好的转化膜,与基体相比,经配方A和B成膜后的试样,其自腐蚀电流密度由34.099μA/cm2分别下降到0.822和1.367μA/cm2,电阻由0.64kΩ.cm2分别增大到32.01和20.96kΩ.cm2。     

Characterization and corrosion protection properties of cerium conversion coating on Gr<Subscript>(f)</Subscript>/Al composite surface

The aim of this work is to investigate corrosion protection properties of Ce conversion coating on the graphite fiber-reinforced aluminum matrix (Gr_(f)/Al) composite surface by electrochemical measurements, and microstructure of the Ce conversion coating was studied by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). It is found that the coating covers the whole surface of Gr_(f)/Al composites as oxidized islands, since there are some micro-cracks on the coating. The Ce conversion coating consists of Ce-rich nano-particles, and the contact sites between particles have some porosity. The porosity is not obvious during initial deposition, however, as deposition time prolonged development apparently. Moreover, some severe cracks may appear during the drying process, since evaporation of water molecules would cause shrinkage and large stress is induced. In addition, pretreatment of surface has an effect on the formation of cracks. Ce conversion coating has the composition of Ce³⁺ and Ce⁴⁺. Deposition of Ce-rich coating on Gr_(f)/Al composite surfaces shifts the polarization curves toward lower current density values. Electrochemical impedance spectroscopy (EIS) data show that Ce conversion coating improved corrosion resistance as compared with samples that have no coating.     

XPS Analysis of the Cerium Conversion Coating on the Anodized Al6061/SiCp

A method of concentration analysis based on X-ray photoelectron spectroscopy (XPS) results was introduced. The concentration of Ce-rich conversion coating on the anodized Al based metal matrix composites Al6061/SiCp was then studied according to this method. The results revealed that the Ce conversion coating on the anodized Al6061/SiCp consisted of Al oxide, Ce oxide and Ce hydroxide. The state of Ce element exhibited the mixture of Ce3+ and Ce4+. Some of Celll was oxidized to be CelV in the outer layer coating.     

Characterisation of surface preparation of 2024 aluminium alloy for conversion coating

Abstract

X-ray photoelectron spectroscopy (XPS), scanning electron microscopy, and electrochemical potentiodynamic experiments have been used to study the pretreatment of 2024–T3 aluminium alloy before conversion coating. The pretreatment process included vapour degreasing, alkaline cleaning and Cr based acidic deoxidising steps. This type of pretreatment is appropriate for conversion coatings which meet aerospace standards for corrosion resistance and paint adhesion. During alkaline cleaning an oxide containing Mg, Zn, Si, and Fe developed on the surface of the alloy. During deoxidation there was dissolution and etching of both the intermetallics and the basic oxide scale left after the alkaline cleaning. Characterisation by XPS indicated that the surface was coated with a thin Cr containing coating after deoxidation which provided a degree of passivation to the surface as determined by electrochemical measurements.

MST/3372     

XPS Analysis of the Cerium Conversion Coatingon the Anodized A16061／SiCp

A method of concentration analysis based on X-ray photoelectron spectroscopy (XPS) results was introduced.The concentration of Ce-rich conversion coating on the anodized Al based metal matrix composites Al6061/SiCp was then studied according to this method.The results revealed that the Ce conversion coating on the anodized Al6061/SiCp consisted of Al oxide,Ce oxide and Ce hydroxide.The state of Ce element exhibited the mixture of Ce^3 and Ce^4 .Some of Cell was oxidized to be CelV in the outer layer coating.     

Investigation on a Non-cyanide Plating Process of Ni-P Coating on Magnesium Alloy AZ91D

In this research we presented a non-cyanide plating process of Ni-P alloy coating on Mg alloy AZ91D. By applying a new process flow of electroless nickel plating in which zinc coating is used as transition of Ni-P coating on Mg alloy AZ91D, the process of copper transition coating plated in the cyanides bath can be replaced. A new bath composed of NiSO4 was established by orthogonal test. The results show that zinc transition coating can increase the adhesion and pH 4.0 and 95℃, respectively. The present process flow is composed of ultrasonic cleaning→alkaline cleaning→acid pickling→activation→double immersing zinc→electroplating zinc→electroless nickel plating→passivation treatment.The present non-cyanide process of electroless nickel plating is harmless to our surroundings and Ni-P coating on Mg alloy AZ91D produced by present process possesses good adhesion and corrosion resistance.