金属表面腐蚀层及涂层的激光干式清洗研究进展

激光干式清洗方法,因操作简单、清洗过程易于控制等优点,目前应用最为广泛。重点介绍了激光干式清洗在各种金属材质表面不同腐蚀层和涂层清除中的应用,包括有多种钢材表面的锈层,钢材表面的ZrO2、Cr2O3、Al2O3变性层,热轧钢表面高温氧化层,Ti合金表面富氧α相层,合金钢在H2S环境中腐蚀而形成的硫化层,钢、铝合金、钛合金表面漆层,热压成型钢板表面Al-Si涂层以及航空压缩机Ti合金叶片TiAlN涂层等。分类对比了不同清洗对象所需选用的合适激光清洗工艺参数,如波长、脉宽、频率、功率、扫描速率等。金属材料激光干式清洗多选用波长为1064 nm的纳秒激光器,清洗后表面粗糙度可达1μm,且随着能量输入的升高而增大。锈层的去除主要依靠高温烧蚀作用,变性层是由于产生的热弹性应力而剥离,而漆层和涂层则是由于烧蚀气化、热振动、热冲击等机制实现清洗。最后,对激光清洗技术在国内不同工业领域中的应用前景进行了展望。     

Corrosion behaviors of arc spraying single and double layer coatings in simulated Dagang soil solution

Three kinds of single layer coatings of Zn, Zn15Al, 316L stainless steel and two kinds of double layer coatings with inner layer of Zn or Zn15Al and outer layer of 316L stainless steel by arc spraying were developed to protect the metal ends of prestressed high-strength concrete (PHC) pipe piles against soil corrosion. The corrosion behaviors of the coated Q235 steel samples in the simulated Dagang soil solution were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and natural immersion tests. The results show that the corrosion of the matrix Q235 steel is effectively inhibited by Zn, Zn15Al, Zn+316L and Zn15Al+316L coatings. The corrosion rate value of Zn15Al coated samples is negative. The corrosion products on Zn and Zn15Al coated samples are compact and firm. The corrosion resistance indexes of both Zn and Zn15Al coated samples are improved significantly with corrosion time, and the latter are more outstanding than the former. But the corrosion resistance of 316L coated samples is decreased quickly with the increase in immersion time. When the coatings are sealed with epoxy resin, the corrosion resistance of the coatings will be enhanced significantly.     

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。     

大跨度桥梁缆索用钢丝热浸镀层研究综述

综述了热浸镀Zn、Zn-Al和Zn-Al-Mg系合金镀层的性能特点和研究现状。在Zn-Al合金中添加Al元素可以减缓Zn的腐蚀氧化,同时可以在镀层表面形成致密的Al_2O_3薄膜起到屏蔽保护作用。在此基础上,采用Mg合金化,不仅可细化镀层组织,还可抑制疏松腐蚀产物的生成,进一步延长合金镀层的寿命。阐明了桥梁缆索用钢丝热浸镀工艺的特点和不足。采用中性盐雾试验评估了应力加载对桥梁缆索用热浸镀层组织和耐腐蚀性能的影响。应力加载会使镀层表面的腐蚀产物保护层破裂,加快腐蚀进程。同时指出了现有桥梁缆索用钢丝镀层评价标准尚存在一些争议,应结合现行的评价体系,重视讨论和探索新的更合适的评价标准。需要研究新一代(Zn-Al-Mg)合金镀层的制备技术和评价标准,推动具有高耐蚀性的多元合金镀层在桥梁缆索用钢丝上的推广应用。同时,桥梁缆索用钢丝热浸镀层的腐蚀性能应考虑应力加载下的腐蚀破坏和相关机理研究。     

300M钢表面冷喷涂锌镍复合涂层性能研究

目的 研究300M高强钢表面的冷喷涂锌镍复合涂层的涂层性能.方法 采用机械混合的方式将锌粉和镍粉进行混合,利用低温气动喷涂技术在300M高强钢表面制备锌镍复合涂层,采用扫描电子显微镜、能量色散谱和显微硬度测试仪研究涂层的微观组织结构.采用普通中性盐雾加速实验、涂层破损盐雾加速试验及户外暴晒试验,对冷喷涂锌镍涂层的抗腐蚀性能进行综合评价.考核冷喷涂对300M钢基材疲劳性能的影响.结果 根据SEM的表面及截面图片分析,冷啧涂锌镍复合涂层十分致密,且无孔隙及裂纹,涂层的孔隙率平均为0.4％,结合强度40 MPa左右.根据EDS结果分析,锌镍复合涂层中锌的质量分数为85％左右,镍的质量分数为15％左右.锌镍复合涂层的显微硬度为70.8HV0.49.锌镍复合涂层中镍粒子的强化作用,提高了涂层的硬度.冷喷涂锌镍复合涂层具有非常好的抗腐蚀性能,盐雾实验超过770h,即使涂层破损也可以达到600h.户外暴晒实验12个月表面无明显腐蚀,并且冷喷涂对300M钢基材的疲劳性能没有影响.结论 冷喷涂锌镍复合涂层作为抗腐蚀涂层,可以对300M高强钢提供保护.     

Electrochemical characteristics of steel coated with TiN and TiAlN coatings

The corrosion protection characteristics of titanium nitride (TiN) and titanium–aluminum nitride (TiAlN) coatings produced on cemented carbon steel targets were investigated in aqueous sodium chloride solution. All coatings were produced by cathodic arc plasma deposition. The results indicated that it was possible to follow the corrosion behavior of the coated systems over a period of 300–900 h of immersion. It was found that the TiN and TiAlN coatings had a lower corrosion rate (current density), about three orders of magnitude lower than the untreated steel substrates. The metal substrate was actually passive in these experimental conditions, and exhibited an electrochemical impedance response that could be described by means of the same equivalent circuit than for the coating. Nevertheless, the analysis of the impedance parameters allowed for direct information concerning the enhancement of the corrosion resistance of the coated system as compared to the passive uncoated metal substrate to be extracted. The major corrosion mechanism for the coated samples arises from electrolyte penetration in the pores of the deposits, which may eventually lead to the development of localized forms of corrosion.     

热喷涂钢柱10年海水腐蚀行为

采用直流电弧喷涂和火焰喷涂技术,在碳钢管表面沉积了１２种类的Ｚｎ、Ａｌ和Ｚｎ－１３Ａ１涂层在日本的千仓海岸进行海水腐蚀实验,结果表明,在５年暴露期内,所有的涂层均没有发生明显的腐蚀;经７年暴露后,未经封闭和经封闭处理的Ｚｎ涂层在浸泡区出现严重的锈蚀,电弧喷涂并经封孔处理的Ａ１涂层,火焰喷涂并经封孔处理的Ｚｎ－Ａ１涂层和火焰涂并经重涂装的Ａ１涂层显示出优良的耐蚀性能,相比之下,未经封闭处理的火焰喷涂     

Zn,Al 合金涂层在膨润土中的加速腐蚀实验研究

采用高速电弧喷涂技术在16MnR钢基体上制备Zn,Al合金涂层,针对其实际应用环境,设计并通过模拟洞室膨润土填埋环境的加速腐蚀实验对涂层的耐腐蚀性能进行研究。结果表明:随着加速腐蚀时间的延长,Zn,Al系合金涂层的腐蚀速率降低;Zn,Al系合金涂层对16MnR钢的防护作用明显,起到了牺牲阳极的阴极保护作用;与Zn涂层和Zn-Al合金涂层相比,Al涂层表现出较优的耐腐蚀性能。     

Corrosion performance of Zn–Al–Mg coatings in open and confined zones in conditions simulating automotive applications

Panels coated by hot dipping with zinc (HDG), Zn–5Al (Galfan) and Zn–1.5Al–1.5Mg coatings at different thicknesses were phosphated and painted on an industrial line. Crevice panels with non‐painted bare parts modelling conditions in hem flanges, reference panels with open surfaces and formed non‐painted panels were exposed to a cyclic accelerated automotive test. Zn–Al–Mg coatings with the thickness of 10 µm provided similar or even better protection than HDG and Galfan at 20 µm in both confined and open configurations. In comparison to 10‐µm HDG, the Zn–Al–Mg coating delayed red rust appearance in crevices by a factor of 2 and the maximal depth of corrosion in the steel substrate was by 42% lower. Confined areas were more corroded than open surfaces. For HDG, the time to red rust appearance dropped by 50–75%, corrosion attack in steel was from 3.5 to 7 times deeper and mass gain was about 2.3 times higher in crevices than on open surfaces. Corrosion of Zn–Al–Mg may be more affected by local environmental conditions created by the crevice configuration than for HDG. Red rust appearance on formed panels of 20‐µm Galfan, 7‐, 10‐ and 14‐µm Zn–Al–Mg was delayed to 10‐µm HDG by a factor of 2.8, 3.5, 3.8 and >4.5, respectively. No adverse effect of forming was noticed. The results indicate that 2‐ to 3‐fold reduction of the coating thickness for Zn–Al–Mg alloy coatings in comparison to traditional HDG may be possible without compromising the corrosion performance.     

Long-term atmospheric corrosion properties of thermally sprayed Zn,Al and Zn–Al coatings exposed in a coastal area

The long-term atmospheric corrosion properties of thermally sprayed Zn, Al and Zn–Al coatings have been evaluated using an electrochemical impedance measurement and several analytical techniques. All the thermal-sprayed specimens with 100 μm coating thickness have protected the steel substrates. In case of the Zn–Al coating, the red rust was not observed regardless of the coating thickness. The corrosion products were identified by the XRD analysis. Preferential dissolution of zinc was observed on the Zn–Al coating by EPMA analysis. The electrochemical impedance results provided an insight about the surface structures of each thermally sprayed coating.     

Neuere Untersuchungen über das Korrosionsverhalten und Korrosionsschutzmaßnahmen von Leichtmetall-Legierungen im Schiffbau und ähnlichen Anwendungsgebieten

Recent investigations into the corrosion behaviour and corrosion protection of light metal alloys in shipbuilding and similar applications The corrosion of Al and its alloys in seawater is due to the high anion defect concentration in the (natural or artificial) oxide skin; this structure facilitates anion adsorption (in particular adsorption of the small chloride ions), so that Al atoms are dissolved from the crystal and pitting corrosion may appear. This danger can be eliminated by Zn coatings on Al or by coupling Al with galvanized steel. This measure results in a certain anodic protection and an enforced general uniform corrosion. Flame-sprayed Zn coatings turn out to be most efficient while Cd coatings are clearly inferior. On the basis of experience gained with the stell/Al couple important variables affecting the corrosion behaviour are potential difference and current density (area ratio) and, in addition, the formation of electrolyte bridges. It is therefore important to prevent the formation of such bridges by careful sealing; it is necessary, however, to take account of the ageing behaviour of the particular sealant.     

Q235上电弧喷涂Zn55Al涂层在3.5wt%溶液中的腐蚀行为研究

本文使用电弧喷涂通过包套挤压+拉拔的方法制备的Zn55Al伪合金丝材成功的在Q235钢上喷涂出了Zn55Al涂层。通过扫描电镜和微区XRD研究了Zn55Al 伪合金丝材的显微结构。通过浸泡腐蚀实验和电化学方法研究了Zn55Al涂层、Zn15Al涂层和 Al涂层的腐蚀行为,并对比了三种涂层之间的差异。结果表明Zn55Al伪合金丝材由纯锌和纯铝组成,在整个成型过程中没有产生合金化。Zn55Al涂层由层片状的富锌相和富铝相组成。经过20天的浸泡实验,Zn55Al涂层形成了一层致密的钝化膜,比其他两种涂层有更好的耐腐蚀性。Zn55Al涂层的自腐蚀电位大约是-1.25v,高于Zn15Al涂层低于纯Al涂层和Q235基体.电偶腐蚀实验表明,Zn55Al涂层比Zn15Al涂层具有更好的点虎穴保护作用。这些结果说明Zn55Al涂层具有更好的耐腐蚀性和可以给Q235基体提供更强的电化学保护.本文也讨论了Zn55Al涂层的的腐蚀机理。     

Electrochemical corrosion behavior of arc sprayed Zn-Al coatings

Cored wires and high velocity arc spraying (HVAS) technique were applied to produce high Al content Zn-Al alloy coatings on low carbon steel substrates. The electrochemical corrosion behaviors of Zn, Al and Zn-Al coatings were studied with potentiodynamic measurement in 5 % NaCl solution. Compared with pure Zn, pure Al and Zn-15Al coatings, Zn-26Al coatings show a higher corrosion resistance in salt solution. The potentiodynamic polarization tests show that the corrosion resistance of Zn-Al coatings increases as Al content is raised. Pure Al coating exhibits different electrochemical behaviors with other coatings. The corrosion initiated at the micro-pores of the coating and the underlying corrosion mechanism is very similar to that of the pitting corrosion.     

Erosion-corrosion of thermally sprayed coatings in simulated splash zone

The damage of marine steel structures in the splash zone is very severe. Applying thermally sprayed metal coatings is among the most important protective technologies, but the service life of current coatings is limited. In this paper, arc spray was used to prepare four types of metal coatings, that is, aluminum (Al), zinc bottom coating combined with aluminum topcoat (Zn + Al), aluminum-zinc pseudo alloy (Al/Zn) and aluminum-titanium pseudo alloy (Al/Ti) coatings. These metal coatings were sealed with epoxy priming and aliphatic polyurethane topcoat. Erosion-corrosion experiments were carried out on self-made device by simulating the splash zone working environment of steel structures and protective coatings. The results show that all the sealed coatings could improve the steel resistance to erosion-corrosion, and the aluminum-zinc pseudo alloy is the most excellent coating. In the coating failure process, mechanical erosion rather than corrosion is the key factor causing coating erosion-corrosion in splash zone. Improving the anti-cutting properties could help to prolong the coating life.     

微纳分级结构超疏水金属表面的电沉积构筑及性能∗

表面粗糙度和表面自由能是影响材料超疏水特性的两个主要因素。 为了获得同时具有微纳分级结构和低表面能的超疏水金属镀层,在低共熔溶剂中采用先构筑微米尺度结构,再构筑低表面能纳米尺度结构的两步电沉积策略。 利用 SEM、EDS 和 FTIR 观察不同沉积时间(t = 0、0. 5、1 和 2 min)下沉积样品(分别命名为 Zn、Zn / Zn myristate-0. 5、Zn / Zn myristate-1 和 Zn / Zn myristate-2)的表面形貌和成分。 利用接触角测量仪和电化学工作站分析样品的超疏水性、耐腐蚀性、自清洁性及化学稳定性。 结果表明,Zn / Zn myristate 镀层表面呈现由微米尺度的纯锌多面体和纳米尺度的十四酸锌薄片构筑而成的微纳分级结构;随着沉积时间增加,十四酸锌纳米薄片逐渐长大、交联并形成网状结构。 得益于其特殊的表面微纳结构和表面组成,Zn / Zn myristate-2 镀层表现出优异的超疏水(CA = 156. 7±1. 5°、SA = 2. 5±0. 3°)、耐腐蚀和自清洁特性。 稳定性测试表明,Zn / Zn myristate-2 镀层在空气(12 周)和 3. 5 wt. %的 NaCl 溶液(6 d)中表现出优异的超疏水稳定性。     

Zn-Al系列高速电弧喷涂层电化学防腐性能研究

采用粉芯丝材和高速电弧喷涂技术制备高Al含量的Zn-26％Al涂层。通过电化学的方法测试涂层在5％NaCl溶液下的腐蚀行为，并与由实芯丝材纯Zn、纯Al及Zn-15％A1所制备的涂层作比较。结果表明：Zn-26％A1涂层在电解质溶液中表现出更优越的防腐性能。动电位极化测试结果说明zn-Al涂层随着Al含量的增加，其耐蚀性也提高。纯Al涂层的电化学腐蚀行为与其它涂层有明显差异，其腐蚀机理类似于点蚀。     

Enhancement of the corrosion properties of cold sprayed Ti–6Al–4V coatings on mild steel via silica sealer

The pore formation associated with the cold spray process requires the development of an economical sealer to enhance the corrosion resistance of Ti–6Al–4V coatings on a mild steel substrate. Herein, a sound method is developed to seal pores in the cold sprayed Ti–6Al–4V coatings with silica sealer. Potentiodynamic polarization tests in 3.5 wt% sodium chloride electrolyte were employed to investigate the corrosion resistance of cold sprayed Ti–6Al–4V coatings fabricated at two standoff distances (30 and 70 mm) before and after the sealing process. The polarization resistance of cold sprayed Ti–6Al–4V coatings significantly increased by >80% after the sealing process. The electrochemical responses of cold sprayed Ti–6Al–4V were dependant on sealing the pores with agglomerated silica nanoparticles as observed by scanning electron microscopy and energy-dispersive X-ray analysis. The increase in polarization resistance makes the sealer an effective treatment for cold sprayed Ti–6Al–4V coatings used in marine environments and other engineering applications. This sophisticated sealing process can reduce the deposition cost by reducing the thickness of Ti–6Al–4V coatings and increasing their lifetime on metal components.     

Microstructure and corrosion behaviour of arc sprayed Zn–Al–Mg–RE cathodic protection coatings on steel substrates

Abstract

Cored wires and high velocity arc spraying technologies have been used to produce Zn–Al–Mg and Zn–Al–Mg–RE (where RE is rare earth) coatings on A3 steel. The durability of coatings in terms of corrosion resistance is the focus of this paper. To study the effect of RE, Zn–Al–Mg coatings also have been produced as a comparison. The microstructures of original coatings and corroded coatings have been investigated after corrosion tests by SEM and XRD. The potentiodynamic polarisation and electrochemical impedance spectroscopy techniques were carried out to determine the corrosion behaviour of the two coatings in 5% NaCl solution. Metallographic as well as electrochemical corrosion results illustrate that the coatings possess a self-sealing capacity, and that the corrosion products can refine the microstructure and enhance the corrosion resistance. Compared to the Zn–Al–Mg coating, the Zn–Al–Mg–RE coating presents a more obvious and stable self-sealing process.     

Failure of aluminium metal spray/organic duplex coating systems on structural steel

Abstract

Individually, aluminium metal spray (AMS) and organic paints are well established as effective protective coatings for steel substrates. These coatings are also frequently used together as duplex systems where their combination should produce a synergistic effect. However in certain, mainly marine, environments premature failure of such coatings, involving early blistering of the paint, has been observed in service after 3–5 years. This work aims to understand the mechanisms associated with the early failure of the AMS+paint duplex system. Various panels were initially prepared for accelerated exposure using combinations of coatings on blast cleaned steel. Visual inspection after salt spray exposure revealed the presence of white corrosion product, which was confirmed afterwards as Al(OH)₃. Observation of the coating microstructures before and after salt spray exposure confirmed significant local corrosion of aluminium underneath the paint layer. It is suggested that failure of the duplex AMS/paint system initiates by corrosion of the porous AMS underneath the organic layer then progresses by the combined effect of volume expansion due to formation of Al(OH)₃ and cathodic blistering of the paint from the AMS surface.     

Über die Vorbereitung von Metallgegenständen für das elektrophoretische Lackieren

Pretreatment of metal parts for electrocoating Electrocoating requires very careful pretreatment because surface defects and contaminations may have a very negative influence on coating quality (surface structure remains visible, decoloration of bright colors, in particular yellowing). Adhesion and corrosion resistance of the coatings are improved by phosphate coatings (on Fe, Al, Zn); Zn phosphate coats are most suitable on Fe and Zn, and Al phosphate coatings on Al. Coating thickness, however, must not be excessive. The accelerators added to the phosphating baths have a very pronounced bearing and should therefore be carefully selected. The phosphate coatings are partially (by 10%) dissolved in the electrophoretically applied coating.