基于荧光特性的铝合金腐蚀早期预测技术研究

筛选了两种荧光材料，采用在有机硅丙烯酸清漆中添加荧光化合物的方法，在LC4铝合金基材表面上制备成荧光传感涂层，研究了传感涂层中荧光物质的特性变化与铝合金腐蚀的关系，探讨了传感涂层对腐蚀监测的灵敏度.结果表明，所选的两种荧光材料传感涂层能有效监测铝合金基体的腐蚀形貌、位置及速度；当涂层中添加浓度为0.5％、0.8％的荧光材料A时，所获得的传感涂层能有效监测到的最小可见点蚀孔平均半径分别为56.68 μm、44.82 μm；而添加荧光材料B所得到的传感涂层能有效监测到的最小可见点蚀孔平均半径分别为83.70 μm、93.71 μm.     

含N、O络合物光敏智能涂层的制备及其性能研究

用光敏感化合物在紫外可见光照射下能发出荧光的特性，筛选了3种光敏感材料，分别将它们添加在环氧漆中制备光敏智能涂层中，并涂覆在含钪铝合金的表面，对铝合金的早期腐蚀进行监测预警。用荧光光谱研究了光敏材料的荧光特性。通过全浸腐蚀试验和盐雾试验研究传感涂层中光敏物质的荧光特性变化与铝合金腐蚀的对应关系，光学显微及扫描电子显微分析表明荧光特征点处即为铝合金基体腐蚀过程中发生阳极过程的区域。探讨了传感涂层对腐蚀监测的灵敏度，并对光敏智能涂层监测铝合金腐蚀的工作机理进行了分析。结果表明，所选的3种光敏材料均能有效地监测到铝合金基体的腐蚀位置及腐蚀发展过程。     

电弧喷涂Zn-Al伪合金涂层耐腐蚀性能研究进展

通过在钢基体表面制备涂层可以很好地延长钢铁材料的服役时间,减少因腐蚀造成的重大事故和人员伤亡。相较于传统的纯Zn涂层、纯Al涂层以及Zn-Al合金涂层,Zn-Al伪合金涂层能够为基体材料提供长久有效的腐蚀防护,在钢铁材料的腐蚀防护中具有巨大的应用潜力。简述了Zn-Al伪合金涂层电弧喷涂制备工艺的特点;介绍了Zn、Al、Zn-Al合金及Zn-Al伪合金涂层在模拟海洋环境下的腐蚀防护原理;在此基础上从组分、喷涂工艺参数(喷涂距离、喷涂电流和喷涂电压)、元素掺杂(Mg、Si及Re)及后处理工艺(封孔、激光重熔)等角度,论述了其对Zn-Al伪合金涂层耐蚀性的影响;讨论了Zn-Al伪合金涂层防腐体系在桥梁、海洋钢结构件、地下运输管道中的应用现状;最后总结了目前研究工作中存在的挑战,提出了电弧喷涂Zn-Al伪合金涂层尚需深入研究的重点问题,为提高钢铁材料使用寿命提供了参考。     

Al对低中子吸收截面Ti-Zr-Nb高熵合金的微观结构和腐蚀行为的影响

针对Al对低中子吸收截面Ti-Zr-Nb系高熵合金的微观结构和腐蚀行为进行了研究。比较了不含Al和含15at%Al的Ti-Zr-Nb合金的相图、微观结构、氧化行为和腐蚀行为。相图计算结果表明,在熔点下Ti-Zr-Nb三元合金为bcc相,添加的Al会倾向于在合金中形成不同的金属间化合物,而缩小相图中bcc单相区的温度区。XRD和TEM结果表明,熔炼获得的Ti-Zr-Nb三元合金为简单的bcc结构,而Al会导致晶体结构转变为有序的B2结构。通过热重分析和高压釜试验对Ti-Zr-Nb系高熵合金的腐蚀行为进行了研究。结果表明,在腐蚀过程中,Ti-Zr-Nb三元合金的氧化膜容易发生剥落,而添加Al会提高氧化层的稳定性,但不会改变腐蚀氧化层的主要氧化物种类。通过计算反应速率常数和激活能对氧化动力学进行了研究,发现添加Al的Ti-Zr-Nb系合金的高温氧化性能与Zr合金接近。     

海洋工程用钢表面喷涂Zn、Al和Zn-55%Al伪合金涂层的耐蚀性

热喷涂金属涂层是当前海洋环境下钢结构件防腐的首选方法,利用电弧喷涂技术在新型海洋工程结构用钢(Q345B钢)表面制备了Zn-55%Al伪合金热喷涂涂层,并与纯Zn涂层和纯Al涂层的耐蚀性进行了对比。结果表明:纯Zn涂层能提供较好的电化学阴极保护作用,但电化学性能欠佳;纯Al涂层表现出优良的电化学性能,但腐蚀后期产生点蚀;Zn-55%Al伪合金涂层具有更优越的耐蚀性和腐蚀防护性能。     

高温海洋环境下过渡金属基合金的腐蚀与防护研究进展

综述了高温海洋腐蚀环境的类型,以及各类合金在不同环境下的腐蚀失效机理。重点考察了Fe、Ti、Ni基合金内部的主要元素在高温下的扩散行为,及其与侵蚀性离子之间的交互作用。从盐雾腐蚀以及熔融热腐蚀2个角度,讨论了化学/电化学反应发生的可能性。基于氧化腐蚀过程中复合氧化膜的形成过程,总结了氧化膜与侵蚀性离子以及杂质气体的再作用机理,明确了保护性氧化膜和非保护性氧化膜的类型。从合金化的角度,揭示了Cr、Al等元素对防腐性能提升的关键作用,指出了材料计算在高温海洋环境的潜在应用价值。最后归纳了高温海洋环境下的涂层防护手段和材料体系,其中结构稳定性和界面反应问题是涂层材料研究的重点。在未来研究方向上,指出应该重点关注腐蚀过程中活性元素的交互作用以及钝化膜的形成机理,筛选有效防护元素。利用氧化、盐雾等多种腐蚀条件,依托构效关系进行涂层优化,形成系统的海洋高温涂层防护方案。高熵合金涂层作为新兴体系在高温防护上的应用具有研究价值。     

Al及Al合金在舟山海域的腐蚀行为

报告Al及Al合金在舟山海域的飞溅区、潮差区和全浸区3种试验条件下暴露2、4、8年的腐蚀结果及其在海水环境中的腐蚀行为.Al及Al合金在海洋环境中的平均腐蚀率较低,主要因点蚀、缝隙腐蚀而受到破坏,硬Al、超硬Al的包Al层对基体起着牺牲阳极保护作用.在飞溅区,Al及Al合金对局部腐蚀较敏感,点蚀密度较大.在飞溅区,二种带包Al层的LC4CS(BL)、LY11CZ(BL)耐蚀性较好,L3M和LF11M的耐蚀性较差;在潮差区和全浸区180YS和LF2Y2表现出较好的耐蚀性.LF11M在潮差区的耐蚀性较好,而在飞溅区和全浸区的耐蚀性较差.     

稀土La对精铸Cu-Ni-Fe-Al合金组织和电解性能的影响

针对Cu-Ni-Fe合金惰性阳极在铝电解过程中高温氧化和耐腐蚀性能差等问题,采用真空熔炼法制备了Cu-Ni-Fe-8Al合金,同时制备了不同La含量的Cu-Ni-Fe-8Al-xLa(x=0,1,2,质量分数)合金,研究了Al、La的添加对Cu-Ni-Fe合金微观组织结构及电解腐蚀性能的影响。结果表明,添加Al元素后,合金在高温电解过程中形成铝酸盐,抑制了Cu的外扩散;添加稀土La提高了氧化膜层与基体的结合性,进一步降低阳极材料的腐蚀损耗,但过高的La添加在一定程度上加速了合金的腐蚀。因此,添加适量Al和微量稀土La的Cu-Ni-Fe-8Al-La合金有望成为惰性阳极铝电解用备选阳极材料。     

AISI 316不锈钢和Ti6Al4V合金在海水环境中的腐蚀与腐蚀磨损行为(英文)

采用立式万能销盘腐蚀磨损试验机研究AISI 316不锈钢和Ti6Al4V合金在海水中与Al2O3陶瓷对磨时的腐蚀与腐蚀磨损行为,重点讨论腐蚀磨损之间的交互作用。结果表明,摩擦作用使得Ti6Al4V合金和316不锈钢的开路电位大幅下降,腐蚀磨损过程中的电流密度远高于静态腐蚀时的电流密度,摩擦明显促进了合金的腐蚀。两种合金在海水中的磨损量远大于在纯水中的磨损量,腐蚀促进了磨损,并且Ti6Al4V合金的耐磨性优于316不锈钢的耐磨性,腐蚀磨损之间的交互作用是材料损失的一个重要因素。本实验所用的摩擦装置为单向滑动的面面接触方式,这使得摩擦对腐蚀的促进作用在总磨损量中所占的比例很小。     

应力作用下2B96K Al-Li合金的腐蚀行为研究

通过测量动电位极化曲线、电化学阻抗谱（EIS）,并结合SEM研究恒应力作用下2896K Al—Li合金在3．5％NaCl溶液中的腐蚀行为。结果表明,应力增加,材料腐蚀加剧;合金主要腐蚀类型为点蚀发展形成的均匀腐蚀,是由于合金的主要强化相为T1（Al2CuLi）和。相,晶界平衡相为T2（Al6CuLi3）相,微量Zn的添加有利于合金基体点蚀或均匀腐蚀形成和发展,从而抑制晶间腐蚀的发展。与2195Al-Li合金在不同应力下的腐蚀行为相比较,应力对2896K Al—Li合金腐蚀的影响较小。     

Use of acoustic emission technique for the early detection of aluminum alloys exfoliation corrosion

Exfoliation corrosion of aluminum alloys is a form of localized corrosion which affects many industries, specially aeronautics. The study of this corrosion mode using only electrochemical techniques is not fully efficient for the detection and control on line of this phenomenon. Therefore, we developed a non-destructive testing technique based on the acoustic emission recordings in order to follow-up this form of corrosion on aluminum alloys. Indeed, recent works have shown the interest of the acoustic emission for the detection, the monitoring and the localization of pitting corrosion on aluminum alloys. This pitting corrosion phenomenon is currently well understood and the experimental methodology acquired during that study is transposed to the study of exfoliation corrosion of aluminum alloys.The present study is conducted on two aluminum alloys: (Al 2024 T3, and Al 7449 T6 and T7). Samples are immersed 4 days in the modified ASTM STP 1134 saline solution. Observations of the structures after tests show that the exfoliation corrosion sensitivity of alloy 7449 T6 is more important than for alloy 7449 T7 which exhibits only the presence of small and non-occluded pits. Very severe exfoliation corrosion was also observed on Al 2024 T3, but after a longer immersion time or in a more acid solution.The recording of the acoustic emission activity shows evident links between this activity and the exfoliation corrosion rate. The analysis of the signal's characteristics reveals a population corresponding to the release of hydrogen bubbles. A few more energetic signals have also been observed. Their source can be either, the cracking resulting from the separation of sheets of metal, or the development and evolution of hydrogen bubbles formed inside blisters during exfoliation corrosion.     

Statistical model for intergranular corrosion growth kinetics

A statistical model has been developed to predict the anisotropy of intergranular corrosion (IGC) kinetics and effect of microstructure on IGC kinetics in high strength AA2024-T3 alloys. The methodology is to estimate the statistical distribution of minimum IGC path length that will be found through the thickness of a given thickness ST sample using the principle of order statistics. A brick-wall model is adopted for wrought Al alloy microstructure and different distributions of grain dimension are assumed for the purpose of the estimation of total IGC path length. Numerical stimulation using a gamma distribution model stimulated the anisotropy of localized corrosion in AA2024-T3 alloys, which quite agrees with the growth rate anisotropy experimentally determined by the foil penetration technique. Some limitations regarding the statistical model are discussed. The statistical model provides a new approach to predicting and quantifying localized corrosion kinetics on basis of the alloy microstructure.     

Microstructural evolution and corrosion behavior of directionally solidified FeCoNiCrAl high entropy alloy

The FeCoNiCrAl alloys have many potential applications in the fields of structural materials, but few attempts were made to characterize the directional solidification of high entropy alloys. In the present research, the microstructure and corrosion behavior of FeCoNiCrAl high entropy alloy have been investigated under directional solidification. The results show that with increasing solidification rate, the interface morphology of the alloy evolves from planar to cellular and dendritic. The electrochemical experiment results demonstrate that the corrosion products of both non-directionally and directionally solidified FeCoNiCrAl alloys appear as rectangular blocks in phases which Cr and Fe are enriched, while Al and Ni are depleted, suggesting that Al and Ni are dissolved into the NaCl solution. Comparison of the potentiodynamic polarization behaviors between the two differently solidified FeCoNiCrAl high entropy alloys in a 3.5%NaCl solution shows that the corrosion resistance of directionally solidified FeCoNiCrAl alloy is superior to that of the non-directionally solidified FeCoNiCrAl alloy.     

Rauschuntersuchungen zur Spaltkorrosion

Noise measurements on crevice corrosion The importance of Al‐Mg‐Si‐alloys as an alternative to Al‐Cu‐Mg‐alloys has continuously increased in aircraft industry over the recent years. Al‐Mg‐Si‐alloys are corrosion resistant under normal atmospheric conditions. However localised corrosion, especially crevice corrosion, can be very dangerous. Pitting or crevice corrosion can be divided into an initial state and a propagation state of corrosion. The transition of a corrosion system from the passive state into the initial state of localized corrosion is characterised by the small fluctuation of the current and the potential. The measurement of this fluctuation is the subject of the electrochemical noise analysis (ENA). Therefore ENA leads to extensive knowledge about the activity of the corrosion system already in the pre‐damaged state. With the help of ENA the influence of crevice condition, potential and time on the initial state of the crevice corrosion on AA 6013 can be demonstrated.     

The localized corrosion of Al 6XXX alloys

This paper presents some recent findings on localized corrosion with a focus on Al 6XXX alloys and on the current times resistance (IR) voltage that exists between the separated anodic and cat hodic reactions. Some newly developed concepts help quantify the relationship between the IR voltage and the polarization curve that exists on the crevice wall, thereby providing for a deeper understanding on how crevice corrosion occurs in many metals and alloys. A signature of the IR voltage form of crevice corrosion in metal/electrolyte systems is the existence of an active/passive transition in their polarization curves. An aluminum/electrolyte system has been found to undergo this form of crevice corrosion. Some new results on intergranular corrosion in Al 6XXX alloys are also presented. For more information, contact B.A. Shaw, The Pennsylvania State University, Department of Engineering Science and Mechanics, University Park, Pennsylvania 16802; (814) 865-7828; fax (814) 865-0122; e-mail bas13.psu.edu.     

General and localized corrosion of magnesium alloys: A critical review

Magnesium (Mg) alloys as well as experimental alloys are emerging as light structural materials for current, new, and innovative applications. This paper describes the influence of the alloying elements and the different casting processes on the microstructure and performance of these alloys and corrosion. It gives a comprehensible approach for the resistance of these alloys to general, localized and metallurgically influenced corrosion, which are the main challenges for their use. Exposure to humid air with ∼65% relative humidity during 4 days gives 100–150 nm thickness. The film is amorphous and has an oxidation rate less than 0.01 μm/y. The pH values between 8.5 and 11.5 correspond to a relatively protective oxide or hydroxide film; however above 11.5 a passive stable layer is observed. The poor corrosion resistance of many Mg alloys can be due to the internal galvanic corrosion caused by second phases or impurities. Agitation or any other means of destroying or preventing the formation of a protective film leads to increasing corrosion kinetics. The pH changes during pitting corrosion can come from two different reduction reactions: reduction of dissolved oxygen (O) and that of hydrogen (H) ions. Filiform corrosion was observed in the uncoated AZ31, while general corrosion mainly occurred in some deposition coated alloys. Crevice corrosion can probably be initiated due to the hydrolysis reaction. Exfoliation can be considered as a type of intergranular attack, and this is observed in unalloyed Mg above a critical chloride concentration.     

Corrosion behavior of aluminum weld overlay alloys with dispersed niobium carbide particles in sodium chloride solution

Aluminum overlay weld alloys with dispersed niobium carbide particles (NbCp/Al) were prepared by a plasma transferred arc welding process. The corrosion behavior of the NbCp/Al alloys was studied in sodium chloride solution by means of electrochemical techniques and scanning electron microscopy. The aluminum alloys under investigation were pure aluminum, aluminum-magnesium, aluminum-magnesium-silicon, and aluminum-copper. The addition of NbC particles shifted the corrosion potentials in the positive direction. However, the pitting potentials were almost similar to that of overlay weld alloy without NbC particles. In the immersion test in quiescent 0.5M NaCl open to the air, preferential localized corrosion of all NbCp/Al alloys was observed at the matrix between NbC particles and crystalline phases.     

包铝层对铝合金腐蚀行为的影响

对LC4CS、LY12CZ、LF6M三种铝合金在厦门海域全浸区有、无包铝层的条件下的腐蚀行为及腐蚀数据进行了对比研究。同时,通过自腐蚀电位和电偶电流的测量,对LF6M（包铝）在厦门海域潮差区的反常腐蚀行为进行了分析。     

铝和铝合金的大气腐蚀

综述了铝和铝合金的大气腐蚀研究现状和历史,以及传统的大气暴露试验和室内模拟加速试验所做的工作和不足.在铝和铝合金的大气腐蚀机理方面,传统的实验技术往往不能给出满意的结果.一些原位测量技术,如环境扫描电镜,开尔文探针和红外吸收光谱等已在大气腐蚀研究中应用,为清晰地描述铝和铝合金的大气腐蚀机理提供了有利条件.介绍了环境因素和铝合金的微观结构特点对铝和铝合金,特别是高强铝合金大气腐蚀的影响.      

Factors influencing the susceptibility to intergranular attack,stress corrosion cracking and de-alloying attack of aluminium brass

The occurrence and the severity of intergranular attack (IGA), stress corrosion cracking (SCC) and de-alloying attack in Al brass alloys have been investigated in an acidic chloride-citrate solution. Tests performed on laboratory prepared alloys, in which As and P additions were made in order to cover the whole composition range admitted by various national specifications indicated that the susceptibility to the different forms of localized corrosion, is mainly related to the As and P contents and it can be markedly influenced by tempering treatments and by cold-working. The optimum corrosion performances of Al brass are displayed by alloys containing As in the 0.01–0.04% range and P ? 0.0025%.