镁锂合金表面高锰酸盐转化膜的研究

采用化学转化法在镁锂合金表面制得了结构致密、耐蚀性能较好的高锰酸盐转化膜,研究了转化液中高锰酸盐溶液浓度对成膜效果的影响。实验采用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱(XPS)对所制得转化膜的表面形貌、结构和组成进行了测试。同时,使用动电位极化曲线、电化学交流阻抗谱和腐蚀失重3种方法对镁锂合金及其转化膜的耐腐蚀性能进行了深入研究。结果表明:高锰酸盐转化膜较均匀、平整,间隙较小,转化膜主要由锰的氧化物组成。提高了镁锂合金的耐腐蚀性能,当高锰酸盐溶液浓度为4.0g/L时,转化膜的腐蚀电流密度小、容抗弧大、腐蚀速率低,耐腐蚀性能佳。     

镁锂合金表面锌锰磷化膜的制备与性能表征

采用化学转化法在镁锂合金表面制备了外观深灰色、结构均匀致密、耐蚀性能良好的锌锰磷酸盐转化膜,并研究了磷化温度对磷化膜性能的影响。采用扫描电子显微镜(SEM)、能谱(EDS)仪、X射线光电子能谱(XPS)和X射线衍射(XRD)仪对膜层的表面形貌、化学组成及结构进行了表征。采用动电位极化曲线、电化学交流阻抗(EIS)和腐蚀失重实验对磷化膜的耐蚀性进行了研究。结果表明,锌锰磷化膜主要由Zn、Zn3(PO4)2、MnHPO4、Mn3(PO4)2组成。锌锰磷酸化膜起到了保护镁锂合金的作用,提高了镁锂合金的耐蚀性,当磷化温度为45℃时,磷化膜的腐蚀电流密度最低,腐蚀速率最小,耐蚀性能最好。     

石墨烯掺杂对镁锂合金微弧氧化膜Cl?腐蚀敏感性的研究

为了研究添加石墨烯后镁锂合金微弧氧化膜在不同NaCl浓度下的腐蚀行为,通过向硅酸盐体系电解液中添加石墨烯,在镁锂合金表面制备出改性的MAO(Micro-arc oxidation)膜层,采用电化学极化曲线和阻抗谱方法研究改性膜层对NaCl溶液的腐蚀敏感性。结果表明:石墨烯的添加可有效改善由于微弧放电形成的孔洞及微裂纹等缺陷,提高膜层致密性和耐蚀性;改性的MAO膜层耐腐蚀性能随着NaCl溶液浓度的升高而降低,主要因为在较高的浓度梯度作用下,侵蚀性离子向膜层中扩散速率加快,进而加速了对MAO膜层的腐蚀破坏。     

以硫酸镍为主盐的AZ91D镁合金化学镀镍研究

研究了以硫酸镍为主盐的AZ91D镁合金化学镀镍.采用无铬前处理在AZ91D镁合金表面形成高锰酸盐和磷酸盐化学转化膜,用SEM、EDX、XRD和极化曲线等方法研究化学转化膜和化学镀镍层的形貌、组成及在3.5%的NaCl溶液中的耐腐蚀性能.结果表明,在高锰酸盐转化膜表面形成的化学镀镍层呈胞状,较致密,有微裂纹;在磷酸盐转化膜上形成的化学镀镍层也呈胞状,晶胞大小不均匀,没有微裂纹.镀层厚度均匀,致密,无孔隙.在3.5%的NaCl溶液中的极化曲线表明化学转化膜对镁合金基体的耐腐蚀性能提高不大,经高锰酸盐和磷酸盐前处理的化学镀镍层腐蚀电位分别为-0.48V_(SCE)和-1.12 V_(SCE).以硫酸镍为主盐的经磷酸盐前处理的化学镀镍层较好地提高了镁合金的耐腐蚀性能.     

Preparation of High Corrosion Resistance Ni-Fe-Sm Alloy Films in Reline SystemEI北大核心CSCD

针对在传统水溶液电解质中制备的 Ni-Fe 合金存在表面粗糙且耐腐蚀性能差的问题,在氯化胆碱-尿素离子液体体系 (Reline)中,加入稀土元素 Sm 对 Ni-Fe 合金进行改性,制备 Ni-Fe-Sm 三元合金膜。采用循环伏安测试、塔菲尔测试、扫描电镜、X 射线能谱仪研究金属离子在 Reline 离子液体中的电化学行为、合金膜表面形貌及其耐腐蚀性能。结果表明,Ni(Ⅱ)、 Fe(Ⅱ)为一步不可逆还原过程,Ni-Fe-Sm 合金在 Reline 体系中成核机制为三维瞬时成核。合金膜表面各金属元素分布均匀, 微观结构呈瘤状球形颗粒,合金膜表面细致,裂纹少,排布整齐。在 3.5 wt.%NaCl 和 10 wt.%HCl 溶液中,加入稀土元素 Sm, 合金膜的耐腐蚀性能显著提高,当沉积电位为?1.22 V,沉积时间为 20 min 时,自腐蚀电流密度最小,腐蚀速度最低,自腐蚀电位最正,耐腐蚀性能最高。进一步丰富了在 Reline 体系中添加稀土元素提高合金耐腐蚀性能的认识,使其在防护、存储等领域有较好的应用前景。     

镁锂合金表面镍磷合金化处理的研究

超轻型镁锂合金是航天、航空的优质轻型材料,但其性质极其活泼、耐腐蚀性能很差,是制约其推广应用的关键问题,且难于进行表面防腐处理.介绍用ML-20701型镁锂合金表面镍磷合金化粉水溶液,在70～75℃条件下,对表面活化的镁锂合金进行浸泡,在镁锂合金表面沉积耐腐蚀合金膜层,从而提高其防腐性能.这也可作为电镀、电泳的预处理工艺,为镁锂合金采用电镀、电泳涂装进行表面防护装饰,提供了有效解决途径.     

AZ31镁合金磷酸镁转化膜的腐蚀性能（英文）

通过在含Mg~(2+)和 PO_4~(3-)离子的溶液中进行浸泡,在AZ31镁合金上制备磷酸镁转化膜以增强其抗腐蚀性能。经磷化处理20 min后,AZ31镁合金上的磷酸镁转化膜呈微裂纹状结构,厚度均匀(约为2.5μm)。X射线能谱分析和X射线光电子谱分析表明,磷酸镁转化膜由磷酸镁和氢氧化镁或氧化镁组成。磷酸镁转化膜对AZ31镁合金可起到强烈的保护作用。磷酸镁转化膜的腐蚀电流大幅降低,约为未覆膜表面腐蚀电流的3%。在0.5 mol/L Na Cl溶液中的腐蚀恶化时间由10 min延长至24 h     

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。     

镁锂合金腐蚀行为及干法镀膜防护工艺研究

目的利用PVD磁控溅射技术,在样品上沉积纯铝膜,以提高镁锂合金的耐腐蚀性能。方法采用动态极化曲线、交流阻抗方法研究镁锂合金在去离子水和3.5%Na Cl溶液两种介质中的电化学行为,并利用感应耦合等离子体发射光谱仪技术和荧光金相显微镜,分别测定合金的成分,分析微观组织结构。采用扫描电子显微镜和EDS能谱仪分析镁锂合金纯铝膜的组织形貌与结构成分。此外,采用电化学技术测试纯铝膜的保护行为。结果在3.5%Na Cl溶液中,镁锂合金的腐蚀电流密度比去离子水介质中的高约两个数量级,且腐蚀电位较负;交流阻抗结果显示,比去离子水中的阻抗模值低一个数量级,说明镁锂合金抗Cl?侵蚀的能力较差。通过磁控溅射技术,获得了厚度为4μm致密的纯铝膜。镀铝后,镁锂合金的腐蚀电流密度降低了约一个数量级,腐蚀电位正移,耐蚀性提高。结论致密的纯铝膜在3.5%Na Cl溶液介质中容易发生钝化,阻碍Cl?的扩散,进而提高了镁锂合金耐Cl?侵蚀性。     

稀土铝黄铜在NaCl溶液中腐蚀行为的研究

设计了一种无砷的HAl77-2-Re耐腐蚀铝黄铜.利用失重法、电化学测试、X射线衍射分析、扫描电镜与能谱分析等手段研究了这种稀土铝黄铜在NaCl(3.5%)溶液中的耐腐蚀性能及其腐蚀行为.结果表明:在稀土铝黄铜的腐蚀过程中,稀土参与了表面腐蚀产物膜的形成,增大了极化电阻,抑制了腐蚀的进行,提高了合金的耐腐蚀性能;与含砷铝黄铜相比,表现出了较好的耐腐蚀性能.     

A novel phosphate conversion film on Mg-8.8Li alloy

The super light Mg-Li alloys exhibit excellent formability due to the addition of lithium, but the corrosion resistance is deteriorated. A novel conversion film is developed to improve the corrosion resistance. The surface morphology of conversion film was observed using scanning electron microscopy (SEM). The chemical composition was analyzed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The corrosion behaviors of Mg-8.8Li alloy and conversion film were investigated with electrochemical and immersion tests. The experimental results indicated that the Mg-8.8Li alloys with and without the protection of conversion film can both be used in NaOH solution safely. But the Mg-8.8Li substrate was susceptible to corrode in NaCl and Na₂SO₄ solutions, and the conversion film can prevent them from corroding. Compared with the NaCl solution, the Na₂SO₄ solution was a strong corrosive medium to the conversion film.     

纯Mg和Mg-15Li合金在弱碱性NaCl溶液中的腐蚀行为

    采用开路电极电位与时间的关系曲线、极化曲线、电化学阻抗谱、扫描电子显微镜及失重法等手段研究了纯Mg和Mg-15Li合金在pH=10.5的3.5%NaCl溶液中的腐蚀行为.结果表明：在弱碱性的环境下,纯Mg和Mg-15Li合金均不耐腐蚀,腐蚀初期,纯Mg比Mg-15Li合金的耐蚀性高一些,经过24h腐蚀后,纯Mg表现为特异活性点的腐蚀,腐蚀坑大而深,Mg-15Li合金则表现为全面点腐蚀.     

Corrosion characterization of Mg-8Li alloy in NaCl solution

The corrosion mechanism of Mg-8Li alloy in NaCl solution was investigated by electrochemical testing and SEM observation. The electrochemical results indicated that the corrosion resistance of Mg-8Li alloy in 0.1 M NaCl solution gradually deteriorated with increasing of immersion time expect for 2 h immersion, which was consistent with the SEM observation of corrosion morphology. Mg-8Li alloy exhibited filiform type of attack under significant anodic control of magnesium solution reaction. The cathodic reaction was driven by hydrogen evolution reaction. The presence of filiform corrosion also proved a resistant oxide film naturally formed on the surface of Mg-8Li alloy.     

Influence of Ca on mierostructure and corrosion resistance of Mg-14Li alloy

In order to improve the corrosion resistance of magnesium lithium alloy, Mg-14Li alloy with different content of Ca (0, 3, 5, 10wt.%) was prepared with a induction melting furnace. Electrochemical test and corrosion test were carried out in NaCI solution with different Cl^- concentrations. The results indicate that the microstructure of the Mg-14Li alloy with Ca consists of dendritic β phase and eutectic structure (β+CaMg₂). With the increase of Ca addition from 0, to 3, 5, 10wt.%, the corrosion resistance of the Mg-14Li alloy initially increases first and then decreases, and that of alloy with 3% Ca is the best. Therefore, the corrosion resistance of Mg-14Li alloy in NaCI solution can be effectively improved by adding proper amount of Ca. In addition, the concentration of Cl^- was one of important factors affecting the corrosion resistance of the Mg-14Li alloy, and the influence of Ca was slighter than that of Cl^-.

     

Chromate conversion coating treatments for electrodeposited zinc-iron alloy coatings from an acidic sulphate bath

The composition, microstructure and morphology of a zinc-iron alloy deposit obtained from an acid sulphate bath have been investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that under the optimised conditions, the bath produced smooth, uniform, bright, fine-grained zinc-iron alloy deposits having the desired 0.4–0.8 wt.% Fe. The zinc-iron alloy deposit was identified as h.c.p. η—phase and showed an highly preferred orientation. A low concentration Chromate treatment has been successfully developed and applied to electrodeposited zinc-iron alloy coatings with 0.4–0.8 wt.% Fe. The corrosion resistance of the Chromate conversion coatings on zinc-iron alloy deposits has been assessed using the neutral spray tests and electrochemical measurements. The results indicated that the corrosion resistance of the zinc-iron alloy deposit was significantly improved and strongly depended on iron content of the alloy deposit after Chromate passivation treatment. The composition depth-profile of the Chromate conversion coating was measured by sequential use of X-ray photoelectron spectroscopy (XPS) and sputter-etching. It was found that the major constituents of the Chromate conversion coating were zinc, chromium and oxygen, and a small amount of iron was also detected. According to analysis of the XPS data, the Chromate conversion coating on the zinc-iron alloy deposit is mainly composed of oxides and hydroxides of zinc and chromium. SEM investigation indicated that the surface morphology of the Chromate conversion coating was characterised by some ‘dried riverbed’ microcracks.     

镁合金稀土镧化学转化工艺研究

镁合金稀土转化膜技术是近年来发展起来的一种环保型镁合金表面处理新技术。通过正交试验对压铸镁合金AZ91D稀土镧化学转化处理工艺进行了研究。利用扫描电子显微镜(SEM)、能量色散谱(EDS)和X射线光电子能谱(XPS)研究了膜层的表面形貌及其组成,并通过容量法对膜层在5%NaCl(pH=6.8~7.0)溶液中的耐腐蚀性能进行了研究。结果表明:La转化处理工艺能够在压铸镁合金AZ91D表面形成均匀、完整的转化膜;膜层主要由La2O3和MgO以及少量的Al2O3组成;La转化膜在浸泡初期的10 h内耐腐蚀性能与铬酸盐转化膜相当。     

AZ91D镁合金表面转化膜腐蚀及防护涂层性能研究

采用高锰酸盐、钼酸盐、锡酸盐转化液分别对AZ91D镁合金进行表面化学转化,得到三种不同的化学转化膜。分别通过SEM、EDS和全浸试验研究不同转化膜的表面微观形貌、成分和腐蚀率,通过划格法和中性盐雾试验法研究转化膜外部有机涂层的附着性能和耐蚀性能。结果表明,高锰酸盐和钼酸盐转化膜表面具有大量微细裂纹,锡酸盐转化膜表面呈鱼鳞状,均为后续涂装提供了具有一定粗糙度的表面。锡酸盐转化膜的耐蚀性最好,高锰酸盐转化后并涂层的附着力和耐蚀性能最好。     

Mg-14Li-1Al-0.1Ce合金在NaCl溶液中的腐蚀行为

采用电化学方法研究了Mg-14Li-1Al-0.1Ce合金在NaCl溶液中的腐蚀行为,采用扫描电镜观察腐蚀后的表面形貌,用失重法测试腐蚀速率,用X射线衍射(XRD)分析了腐蚀层和溶液中腐蚀颗粒的组成。结果表明,Mg-Li-Al-Ce合金的腐蚀速率随溶液Cl-浓度增大而增大,由失重法所得到的腐蚀速率远大于由腐蚀电流密度(Jcorr)计算所得的腐蚀速率。扫描电镜(SEM)观察表明,合金表面随溶液Cl-浓度增加而破坏严重。腐蚀产物层没有保护作用,在腐蚀产物下有明显的蚀坑和裂纹。XRD表明腐蚀产物层和溶液中腐蚀颗粒由Mg(OH)2、Li0.92Mg4.08和Li3Mg7组成。     

Preparation of calcium phosphate coatings on Mg-1.0Ca alloy

The calcium phosphate coatings were prepared by virtue of electrochemical deposition in order to improve the corrosion resistance of Mg-1.0Ca alloys in simulated body fluids.The chemical compositions,structures and morphologies of the coatings were investigated by energy dispersive spectroscopy(EDS),X-ray diffractometry(XRD)and scanning electron microscopy(SEM), respectively.The potentiodynamic electrochemical technique was employed to investigate the bio-degradation behavior of Mg-1.0Ca alloys with Ca-P coatings in Hank's solutions.The experimental results show that the deposited coatings predominately consist of flake-shape brushite(DCPD,CaHPO4·2H2O)crystallites.The corrosion resistance of the substrates with coatings is improved in Hank's solutions significantly.