2024Al和SiCp／2024Al基复合材料阳极氧化膜的耐蚀性

用动电位阳极极化和电化学阻抗技术研究了SiCp／2024Al复合材料硫酸阳极氧化膜在3．5％NaCl水溶液中的耐蚀性；作为比较，对2024Al的阳极氧化膜耐蚀性也进行了研究。结果表明，经阳极氧化处理的SiCp／2024Al复合材料具有良好的耐NaCl溶液腐蚀的能力，其腐蚀速度较未处理的样品降低了2个数量级以上。但其耐蚀性不如2024Al合金的阳极氧化膜。这是由于氧化膜中SiC颗粒的存在破坏了氧化膜的完整性和均匀性所致。对SiCp／2024Al MMC，采用小电流密度来进行阳极氧化处理，可获得较好的防护效果。此外，阳极氧化膜层的抗蚀性随浸泡时问的增加有降低的趋势。     

SiCp/Al基复合材料的耐蚀性研究

用电化学方法和腐蚀失重法研究了2024Al和SiCp/2024Al基复合材料在3．5％NaCl水溶液中的耐蚀性,用电化学交流阻抗技术对它们的硫酸阳极氧化膜的耐蚀性进行了研究。结果表明,SiCp/2024Al复合材料在3．5％NaCl水溶液中比相应的基体金属有较大的腐蚀敏感性。SiCp/2024Al的阳极氧化膜耐NaCl溶液腐蚀能力不如2024Al合金的阳极氧化膜,是氧化膜中SiC颗粒的存在破坏了氧化膜的完整性和均匀性。     

SiCP/2024Al复合材料的阳极氧化研究

为了研究SiCP/2024Al复合材料阳极氧化的保护效果,用电化学方法、浸泡试验和盐雾试验研究了该复合材料及相应的施加阳极氧化保护试样在3.5%NaCl溶液中的腐蚀行为,并用扫描电子显微镜(SEM)对腐蚀形貌和氧化膜的微观形态进行了观察.结果表明:SiCP/2024Al经过阳极氧化后在3.5%NaCl溶液中的耐蚀性明显提高,Ecorr和Epit正移150 mV,Icorr从3.650 μA减小到0.358 μA,腐蚀速率由0.336 mm/a下降到0.122 mm/a;虽然SiC颗粒的存在影响了阻挡层的连续性,但多孔层仍能在电解质/材料界面不断生成,并且多孔层上的孔隙可以在封孔过程中得以闭合.     

2024铝合金阳极氧化、电解着黑色工艺优化及膜的性能

为了在2024铝合金表面获得结合力好、耐候性好及黑色纯正的阳极氧化膜,首先在硫酸电解液中对2024铝合金进行阳极氧化,之后在Sn-Ni-Cu-Co电解液中进行电解着黑色,采用SEM,XRD,EDS分析膜层的表面形貌、截面特征、成分及膜中的元素分布,优选了阳极氧化、电解着色电解液的成分;从金属颗粒沉积、氧化还原方面分析了电解着色的机理。结果表明:最佳阳极氧化液配方为100.0 g/L H2SO4,5.0 g/L H3BO3,2.0 g/L(NH4)2SO4,2.0 g/L苹果酸,2.0 g/L MgSO4,1.5 g/L Al2(SO4)3;最佳着色液配方为15 g/L SnSO4,10 g/L NiSO4,10 g/L CuSO4,10 g/L C4H6O4Co,3 g/L FeSO4;在Sn-Ni-Cu-Co电解着色液中,Sn2+,Co2+,Cu2+等通过还原反应以单质的形式沉积于氧化膜层的孔隙或底部,通过多重散射使氧化膜颜色加深,从而得到了黑色的氧化膜;最佳氧化膜颜色为石墨黑,结合力及耐候性均较好。     

钛合金阳极氧化着色技术的研究进展

阳极氧化着色技术是一种在Al、Mg、Ti等有色金属及其合金表面原位生长氧化膜的传统技术.用该技术制成的氧化膜色彩均匀鲜艳,结合力高,具有优良的耐腐蚀性和生物相容性,已广泛应用于生物医学和航空航天领域.介绍了氧化钛膜的发色原理,综述了阳极氧化着色技术在国内外的研究现状,概括了阳极氧化着色的工艺方法、氧化钛膜制备过程的影响因素和钛合金阳极氧化的应用领域,并展望了该技术的应用前景.     

建筑铝型材表面氧化膜的制备及其性能

目前,有关阳极氧化工艺参数对铝合金型材表面氧化膜的组织及性能影响的系统研究不多。对建筑用2024铝合金、7075铝合金和6063铝合金进行了表面阳极氧化改性处理,研究了阳极氧化时间、电流密度和冰乙酸添加量对表面氧化膜层的生长行为、表面形貌、膜厚、显微硬度和弹性模量的影响,并分析了其作用机理。结果表明,2024铝合金和7075铝合金表面氧化膜中都存在显微孔洞缺陷,而6063铝合金表面氧化膜较为致密均匀,没有显微孔洞缺陷存在;相同工艺条件下6063铝合金表面氧化膜的生长速度最快,其次为7075铝合金,2024铝合金表层氧化膜生长速度最慢;相同工艺条件下3种合金表面氧化膜显微硬度从小至大依次为:2024铝合金7075铝合金6063铝合金;3种合金氧化膜层的弹性模量从小至大依次为:2024铝合金7075铝合金6063铝合金。     

2024铝合金硬质阳极氧化电参数对膜生长规律的影响

至今,还未见铝合金硬质阳极氧化膜生长规律的研究报道。考察了电参数(电流密度、脉冲频率、占空比及脉冲幅值)对2024铝合金硬质阳极氧化膜生长规律的影响,通过SEM及XRD分析了氧化膜的表面形貌及组成结构。结果表明:在不同的氧化体系和电参数条件下,硬质阳极氧化膜向基体内生长的厚度均大于向外生长,并占到总厚度的51%～64%;不同氧化体系和电参数对氧化膜生长规律没有明显的影响,电参数的变化不会改变氧化膜的非晶结构。     

高频氧等离子体制备氧化铝膜的微结构与光学常数

将真空蒸发沉积的Al膜 ,在一台高频等离子体辉光放电的装置中进行阳极氧化 ,得到了光学和电学性能稳定的Al2 O3 膜。Al膜表面氧化层结构是γ Al2 O3 ,在波长 30 0～ 70 0nm范围内折射率为 1 5 3～ 1 34。文章还对用不同方法制备的Al2 O3 膜的折射率的差异进行了讨论     

铝合金阳极氧化对氧化膜显微硬度和粘接性能的影响

为了获得膜层显微硬度和粘接强度都较高的铝合金阳极氧化工艺,通过阳极氧化在2024铝合金表面制备氧化膜,根据正交试验来确定氧化工艺参数对铝合金阳极氧化膜显微硬度和粘接性能的影响,采用X射线衍射仪(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)等分析氧化膜的相组成、化学组成和表面形貌,并研究电流密度对氧化膜厚度的影响以及氧化膜厚度对膜层显微硬度和粘接强度的影响。结果表明:氧化工艺参数对氧化膜显微硬度的影响程度为电流密度电解液中H_2SO_4浓度氧化时间;采用2种胶粘剂粘接后,氧化工艺参数对氧化膜粘接强度的影响程度有所不同,然而电流密度均为最主要的影响因素;经过阳极氧化处理,铝合金表面的显微硬度和粘接强度均有很大提高,快固结构胶的粘接强度比改性丙烯酸酯胶的高;铝阳极氧化膜的厚度随电流密度增加而增大,在适宜的电流密度范围内氧化膜厚度的增加会导致膜层显微硬度和粘接强度的增大;氧化膜的相组成为非晶结构,主要元素为Al和O,均不因电流密度的变化而变化;铝合金阳极氧化膜表面形貌的优劣、孔隙率与氧化膜显微硬度及粘接强度的大小密切相关。     

原位合成TiB2/6351Al复合材料阳极氧化的研究

颗粒增强铝基复合材料强度及模高量,具有很大的应用前景,但增强颗粒的引入使复合材料的耐蚀性大大下降,同时也给其阳极氧化带来困难.为此,将阳极氧化工艺运用于一种原位合成TiB2/6351Al复合材料,研究了阳极氧化液成分、添加剂、氧化电流密度、温度和时间对膜层质量的影响.对膜层的性能测试表明,所得氧化膜大大提高了材料的耐蚀性能.此外,通过对氧化膜表面与截面结构的深入观察,分析了该复合材料氧化膜的生长机理.     

Corrosion Behavior and Protection Efficiency of 2024Al and SiCp／2024Al Metal Matrix Composite

The corrosion resistance of 2024 Al and SiC particle reinforced 2024 Al metal matrix composite(SiCp/2024Al MMC) in 3.5% NaCl solution was investigated with electrochemical method and immersion test, and the corrosion protection of sulfuric acid anodized coatings on both materials was evaluated by electrochemical impedance spectroscopy.The results showed that the SiCp/2024AlMMC is more susceptible to corrosion than its matrix alloy in 3.5% NaCl.For 2024Al,the anodized coating provides excellent corrosion resistance to 3.5%NaCl.The anodized coating on the SiCp/2024Al provides satisfactory corrosion protection,but it is not as effective as that for 2024Al because the structure of the anodized layer is affected by the SiC particulates.     

Corrosion protection and formation mechanism of anodic coating on SiCp/Al metal matrix composite

The corrosion protection from sulfuric acid anodized coatings on 2024 aluminum and SiC particle reinforced 2024 aluminum metal matrix composite (SiC_p/2024Al MMC) in 3.5 wt.% NaCl aqueous solution was investigated using electrochemical methods. The results show that the anodized coating on 2024Al provides good corrosion protection to 3.5 wt.% NaCl, and the anodized coating on the SiC_p/2024Al MMC provides some corrosion protection, but it is not as effective as for 2024Al because non-uniformity in thickness and cavities present are associated with the SiC particulates. Cavities above SiC particles are the reason that the anodized coating on the MMC cannot be completely sealed by hot water as with anodic Al alloy. SiC particle anodizes at a significantly reduced rate compared with the adjacent Al matrix. This gives rise to alumina film encroachment beneath the particle and occlusion of the partly anodized particle in the coating. It was found that the barrier layer of anodized Al MMC is not continuous, and it is composed primarily of the barrier layer of anodized Al matrix and a barrier-type SiO₂ film on occluded SiC particles in the coating. A new formation mechanism of coating growth during anodizing of a SiC_p/2024Al MMC was proposed.     

镁合金微弧氧化陶瓷膜的微观结构、相成分和耐腐蚀性能

为获得耐腐蚀性优良的镁合金表面膜层,在含5 g/L硅酸钠、2 g/L磷酸钠和1 g/L氢氧化钠的复合溶液中,用自制设备对AZ91D镁合金进行了微弧氧化.利用扫描电镜和X射线衍射分析了AZ91D 镁合金表面微弧氧化陶瓷膜的表面形貌、截面结构和相组成.结果表明:AZ91D 微弧氧化陶瓷膜由疏松层和致密层组成,疏松层陶瓷膜疏松,厚度较大,且存在一些孔洞;致密层陶瓷膜与基体金属结合紧密,陶瓷膜主要由MgO,Mg2SiO4,Mg3(PO4)2和MgAl2O4组成.在3.5%的NaCl溶液中,微弧氧化陶瓷膜的自腐蚀电位为-1 390 mV,而镁合金基体的为-1 540 mV,表明经微弧氧化处理后AZ91D 镁合金的耐蚀性有较大提高.     

Corrosion behavior of Ti–Al–N/Ti–Al duplex coating on AZ31 magnesium alloy in NaCl aqueous solution

In this study, Ti–Al–N/Ti–Al duplex coating was deposited on AZ31 magnesium alloy by magnetron sputtering with a Ti/Al composite target. Scanning electron microscopy and Auger electron spectroscopy were applied to investigate the morphology and elemental concentration of the obtained coating, respectively. The top layer was Ti–Al–N film with a Ti:Al:O:N ratio of 0.32:0.84:0.08:1, and the bottom layer was Ti–Al film with a Ti:O:Al ratio of 1.94:0.12:1. Each layer of this coating presented a developed columnar structure. The polarization test and immersion test were used to investigate corrosion behavior of the coated sample in 3.5 wt.% NaCl aqueous solution. The results showed that this duplex coating could protect the substrate effectively in NaCl aqueous solution. Nevertheless, several through-thickness micropores in the coating finally induced the failure of the coated AZ31 in the immersion test.     

Cavitation behavior of active thermal-sprayed coatings

As a first stage in the development of active coatings to improve both localized corrosion resistance and cavitation resistance in sea water, we studied flame-sprayed coatings of aluminum, zinc and Zn-15 wt.% Al applied to steel substrates. Cavitation was carried out in distilled water and in 3.5 wt.% NaCl solution, and was characterized by weight loss and by scanning electron microscopy. Open-circuit potentials in 3.5 wt.% NaCl solution were measured in an attempt to monitor internal fracture, which would allow seepage of solution through the coating to the more noble steel substrate.Cavitation damage rates were found to be significantly higher in the saline solution for the alloy and the aluminum coatings, whereas little sustained change in damage rate was found for the zinc coatings. The data indicate that the strength of the particle matrix essentially governs the overall strenght of the coating. However, in saline solution the effects of alloy strengthening are slightly reduced by the tendency of localized corrosion attack to initiate coating flaws and eventual failure.     

Effect of corrosive media on galvanic corrosion of complicated tri-metallic couples of 2024 Al alloy/Q235 mild steel/304 stainless steel

Galvanic corrosion of tri-metallic couples is more complicated than that of bi-metallic couples. In this study, the effect of the pH of corrosive media on the galvanic corrosion of 2024 Al alloy/Q235 mild steel/304 stainless steel tri-metallic couples was investigated using potentiodynamic polarization, scanning electron microscopy, scanning vibrating electrode technique and a multi-channel galvanic corrosion meter. The results show that 2024 always acts as the only anode in 3.5 wt% NaCl at pH 5.56, 9.72 and 12.0, while both Q235 and 2024 act as anodes at pH 2.39 in the initial stage and then the role of Q235 changes at longer coupling time, which can be attributed to the effect of pH on the surface film of 2024. It is also found that the galvanic current density of a tri-metallic couple is the superposition of two bi-metallic couples when cathodic reactions are controlled by the diffusion of oxygen, otherwise it is smaller than that of the sum of two bi-metallic couples. The localized corrosion instead of uniform corrosion of anodic metal is accelerated by galvanic corrosion.     

Oxidation behavior and electrochemical corrosion performance of Ti<Subscript>3</Subscript>Al alloy with TiAl coating

Magnetron-sputter deposition was used to produce a Ti–48Al–8Cr–2Ag (at. %) coating on a Ti–24Al– 17Nb–0.5Mo (at. %) alloy substrate. Oxidation behavior was studied in air at 900–1000°C. The results indicated that the oxidation rate of sputtered Ti–48Al–8Cr–2Ag nanocrystalline coating was lower than that of the Ti₃Al alloy at 900°C. The former formed a scale of merely Al₂O₃, and the latter formed a scale of TiO₂. However, the Ti–48Al–8Cr–2Ag nanocrystalline coating showed a little bit higher oxidation rate than Ti₃Al alloy at 1000°C because the outer TiO₂ scale formed and columnar boundaries of the coating gave a larger actual oxidation area than the original alloy. The electrochemical corrosion behavior was investigated in a 3.5% NaCl solution at room temperature. The coating showed excellent electrochemical corrosion resistance in 3.5% NaCl solution because it exhibited stable passive polarization behavior without any overpassivation phenomena.     

Ni-P合金在3.5%NaCl溶液中的溶解行为

在铜基体上制备了磷含量为8.3%(质量分数)的化学镀Ni-P合金镀层,采用循环伏安、扫描电镜(SEM)、X光电子能谱(XPS)等方法研究了Ni-P合金在3.5%NaCl溶液中的溶解行为.结果表明,在静态低电位扫描速度下,Ni-P合金的溶解速度增大,而在旋转电极上,低的扫描速度可加速合金进入钝态,而且形成的钝化膜难以还原.合金在高阳极电位下形成的氧化层中含有NiO和PO43-,而且此层中发生了磷的富集.     

Electrochemical study of the corrosion behavior of Ce sealing of anodized 2024 aluminum alloy

The technological process of Ce sealing of anodized LY12 (2024) alloy is introduced in this paper. The corrosion behavior of the film is studied by polarization curves and electrochemical impedance spectroscopy. The results show that the coating remains passive at the potential range from the open circuit potential (−780 mV) to −250 mV. After immersing the sample in NaCl solution for 6 days, the outer layer Ce conversion coating begins to loose its anticorrosive property. The inner Ce sealing anodized film is not corroded until 60 days immersion. Thus, the inner layer Ce sealing anodized film takes the leading role of the corrosion protection for LY12 alloy.     

Polishing-assisted galvanic corrosion in the dissimilar friction stir welded joint of AZ31 magnesium alloy to 2024 aluminum alloy

Galvanic corrosion of a dissimilar friction stir welded 2024-T3 Al/AZ31B-H24 Mg joint prepared using a water-based and a non-water-based polishing solution was characterized. Microstructure and the distribution of chemical elements were analyzed using optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The stir zone polished using water-based solution was observed to be much more susceptible to galvanic corrosion attack than that obtained using non-water-based polishing solution. The location of corrosion attack was observed in the narrow regions of AZ31 Mg alloy adjacent to Al2024 regions in the stir zone. The occurrence of galvanic corrosion was due to the formation of Mg/Al galvanic couples with a small ratio of anode-to-cathode surface area. The corrosion product was primarily the porous magnesium hydroxide with characteristic microcracks and exhibited a low microhardness value.