Corrosion inhibition of aluminum alloys in heat exchanger systems

Corrosion behaviour of AA 3003 and AA 7075 aluminum alloys in tap water has been studied at temperatures ranging from 25 to 95 °C. The effects of additives on the corrosion rates have also been investigated. Experimental results show that the corrosion rates of both AA 3003 and AA 7075 in tap water increase with increasing temperature up to 88 °C. The addition of any one of the following chemicals: chromate, nitrate, molybdate and silicate in tap water results in a significant reduction in corrosion rates of these aluminum alloys, particularly under high temperature conditions. Sodium sulphate has a slight inhibitive effect at temperatures below 88 °C, but its presence in tap water at 95 °C causes an increase in the corrosion rates of both aluminum alloys. An adverse effect on corrosion behaviour, however, is observed when sodium phosphate is added.     

铝合金的晶间腐蚀与剥蚀

综述了近几十年来国内外在2xxx系和7xxx系铝合金及Al-Li合金的晶间腐蚀和剥蚀等研究方面的主要进展.总结了合金中晶界沉淀相的成分、分布及其与晶格的击穿电位差异等对晶间腐蚀的影响规律,探讨了热处理时效状态对合金耐蚀性和局部腐蚀动力学的影响机制.同时探讨了合金的晶格形态、腐蚀产物楔入作用等因素对合金剥蚀过程的影响规律,并对合金的晶间腐蚀和剥蚀研究中所采用的一些快速可靠的无损监检测方法,如电化学阻抗谱（EIS）,进行了评价.     

Behaviour of Cu-Ni alloys in natural sea water and NaCl solution

A series of Cu-Ni alloys, ranging from 30 to 90% copper was studied by electrochemical methods in 3.5% sodium chloride solution and in sea water. The composition of the corrosion layer and of the solution after various immersion times was determined by chemical methods and X-ray diffraction. The results are consistent with a corrosion process involving dissolution of copper and nickel enrichment at the surface. The corrosion resistance of all the alloys is better in NaCl solution than in sea water.     

SEM-EDS characterization of natural products on corrosion inhibition of Al-Mg-Si alloy

The corrosion resistance of aluminum and its alloys is the subject of tremendous technological importance due to their increased industrial applications. The corrosion protections and the mechanism of corrosion inhibitions of natural products for an Al-Mg-Si alloy in seawater were investigated at room temperature. The surface morphology was studied by means of macro scale electrochemical techniques and localized microscopic methods, i.e., Scanning electron microscope (SEM) with associated elemental analysis by energy dispersive spectrometer (EDS). SEM examinations provided morphological characterization of the surface of Al-Mg-Si alloy sample before and after immersion in seawater; meanwhile surface analytical techniques by the EDS allowed us to investigate detail the chemical composition of aluminum oxide layers. The experiments were performed with Al-Mg-Si alloy, immersed in a 5 L beaker containing seawater with and without the natural products for 60 days at room temperature. The SEM results indicate that the natural products (natural honey, vanillin, and tapioca starch) absolutely inhibited the corrosion products on the specimen surfaces. They also protected the passive film from dissolution in seawater. The EDS spectrums were determined that carbonaceous, carbonyl, methoxy and hydroxyl groups as functional groups of natural products in inhibition mechanism.     

6xxx系铝合金表面腐蚀及其防腐的研究现状

6xxx系(Al-Mg-Si)铝合金作为综合性能良好的中强铝合金,因其较小的密度、良好的耐蚀性和成形性等优点,被广泛应用在航空航天、交通运输和建筑机械等领域。然而,该类铝合金在工业应用中依然存在腐蚀问题,造成巨大的经济损失,带来严重的安全隐患。针对这一问题,首先介绍了6xxx系铝合金的腐蚀类型,总结了影响其耐蚀性的影响因素,重点介绍了合金元素对其耐蚀性的影响。已有的研究结果表明:铝合金中的Mg、Si、Cu、Zn等元素显著影响合金的耐蚀性能,过量Si和Cu元素的添加增加了铝合金的晶间腐蚀敏感性;适当地添加过渡族金属元素及稀土元素,可有效改善铝合金的耐蚀性。随后,分析了提高铝合金耐蚀性能的途径,包括改善热处理工艺、优化合金成分及添加复合物等方法,并介绍了几种典型的表面防腐处理工艺,如阳极氧化技术、微弧氧化技术、化学转化膜技术、电镀及化学镀技术。最后总结了以上防护途径存在的一些问题,并指出了耐蚀铝合金的主要发展方向。     

SURFACE ANALYSIS OF ALUMINUM ALLOYS INFLUENCED BY SULFATE REDUCING BACTERIA

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铝合金表面微/纳米结构构筑研究进展

铝合金以其优异的性能而被广泛应用于工业生产的各个领域,通过一系列方法可以在铝合金表面构筑多种类型的微纳米结构。这些微纳米结构可以提高铝合金的摩擦学性能、耐蚀性能、界面结合力、抗结冰性以及装饰性能,对将铝合金应用到更广阔和更苛刻的环境中具有重要意义。介绍了铝合金表面微/纳结构的主要构筑方法。化学刻蚀法制备出了凸台和凹坑的迷宫形貌;阳极氧化法构筑出了高度有序的孔洞结构;微弧氧化法制备出了表面布满微孔的氧化膜;水热法可以构筑形状多样的纳米花朵形貌;电解加工对阴极材料的表面结构进行复刻,可以采用不同比例的阴阳极材料进行大面积的制备。阐述了这些微纳米结构的生长过程,并分析了实验条件(如温度、处理时间、电参数、溶液成分及浓度等因素)对铝合金表面微纳米二元结构生长的影响规律,重点总结分析了其研究现状和影响微纳米结构的因素。通过对现有铝合金表面结构制备方法的总结和分析,展望了其今后的发展趋势。     

Full-scale accelerated tests of aluminum alloys under exposure to marine atmosphere

Dynamics of corrosion of aluminum alloys D16T, V95T2, and 1424TG1 is studied in marine atmosphere at corrosion stations of three climatic zones as dependent on the surface concentration of chlorides. The amount of chlorides on the sample surface depends on the alloy grade: the highest value was characteristic for alloy D16T, and the lowest value was observed on alloy 1424TG1. A predictive estimate is given for corrosion resistance of aluminum alloys as regards the sample weight loss.     

超细晶镁合金的腐蚀与防护进展

总结了近年来经剧烈塑性变形加工后的超细晶镁合金的腐蚀与防护研究。镁合金的初始成分可能对剧烈塑性变形加工后样品耐蚀性的变化起主导性作用。对于纯镁及含有铝或稀土等致钝性元素的合金,如AZ系和WE系镁合金,绝大多数剧烈塑性变形加工会促进生成更致密的保护膜,因而可以提升镁合金的耐蚀性。对于不含此类元素的镁合金体系,如Mg-Zn系合金,由于生成了更多的腐蚀微电偶,等通道转角挤压或高压扭转加工引起的第二相颗粒的细化和分布会加速镁合金的腐蚀,但多轴等温锻造可以提升此类合金的耐蚀性,该技术值得更多的关注。在成分相似的情况下,组织的均匀性或者第二相变化情况的影响可能较晶粒尺寸和织构演变的影响更大。对加工后的镁合金进行热处理或者表面改性是进一步提升其耐蚀性的有效手段。相对于粗晶基体,超细晶基体表面改性后的涂层的耐蚀性往往更好,值得更多的研究关注。     

飞机结构铝合金直接化学镀Ni-P合金研究

高强度铝合金被广泛用于飞机结构中,然而,这一系列铝合金抗腐蚀和耐磨性差,限制了其应用。而Ni-P合金镀层具有高的硬度和抗腐蚀性能等优异特点,成为增强表面性能的常用手段。采用化学镀镍工艺在铝合金（6061）表面进行化学镀镍处理,研究了pH值、沉积温度和沉积时间对沉积速率的影响。分析了化学镀镍层的成分和组织形貌,同时对镀层的硬度、抗腐蚀性进行了表征。试验表明,在铝合金表面化学镀镍可以显著提高铝合金表面的硬度,并改善其在5％NaCl溶液中的耐蚀性。     

两种包铝的高强铝合金受力状态下的大气腐蚀行为

采用U型弯曲加载和模拟大气加速腐蚀试验方法及扫 描电镜，研究了包铝的两种工业高强铝合金LY12和LC4在受力状态下的大气腐蚀行为.结果表明，两种铝合金基体在此模拟大气加速腐蚀试验环境中对晶间腐蚀和应力腐蚀裂开均敏感.晶间腐蚀从局部开始，逐渐向四周扩展.在发生晶间腐蚀部位出现垂直于受力方向的沿晶裂纹，并随试验时间延长裂纹也逐渐加长；合金板材表面具有约90μm厚的包铝层，除点蚀外，这层包铝层未出现其它形式的局部腐蚀，说明包铝层对铝合金基体起到了很好的保护作用.两种包铝高强铝合金板材在包铝层完好时均对晶间腐蚀和应力腐蚀裂开的敏感性差.     

Exfoliation Corrosion of Aluminum Alloys. III. Corrosion Products Converters

The requirements to be met by a converter of the corrosion products (CCPs) of aluminum alloys are formulated, and the technique for expert assessment of its efficiency is developed. Accelerated, field, and strength tests of specimens with the exfoliation corrosion (EC) products incompletely removed were carried out. The effect of both the penetrability of a CCP composition and the surface treatment on the completeness of the EC products transformation and the paint coatings (PCs) adhesion were investigated. The CCP compositions with enhanced physicochemical properties and protective capacity, including those resistant to microbial corrosion, compatible with PCs and exerting no detrimental effect on their adhesion, are revealed.     

慢应变速率下铝合金的腐蚀行为

根据铝合金腐蚀的基本特征，建立了新鲜铝合金瞬时腐蚀速率的计算方法。通过改变试样的应变速率，研究了力学效应对LC4CS铝合金腐蚀电化学行为的影响。结果表明：在恒应变速率作用下，铝合金自腐蚀电位有明显的负移趋势，且应变速率愈大，负移速率愈快。与阳极氧化后的铝合金短路耦合，在应变量大于0.04后，LC4CS铝合金的自溶解电流显示急剧增大的趋势。对同一应变速率而言，随着应变量的增加，新鲜铝合金的瞬时腐蚀速率也随之增大。     

TA16和TA17钛合金在高温高压水中的腐蚀行为研究

研究了TA16和TA17钛合金在高温高压中性水质中的电化学行为、均匀腐蚀行为和应力腐蚀行为.结合SEM和XPS分析技术,分析了腐蚀后合金表面形貌和氧化膜的组成.研究结果表明:在高温高压中性水质中,两种钛合金具有很好的耐腐蚀性能,TA16钛合金的钝化性能、抗均匀腐蚀和抗应力腐蚀性能均优于TA17合金,腐蚀后两种钛合金表面生成了表层由TiO2组成、内层由TiO2、Ti2 O3和TiO组成的致密氧化膜.     

铝和铝合金的大气腐蚀研究现状

综述了铝和铝合金的大气腐蚀特点和大气主要污染组分对铝的大气腐蚀影响. 暴露于大气中的铝表面呈现三层结构, 即氧化铝和氢氧化铝层、其上的腐蚀产物层和最上层的污染物沉积形成的污染物层. 铝的硫酸盐是大气腐蚀层最丰富的腐蚀产物, 其次是铝的氯化物. 着重阐述了SO2, NO2, NO, O3, Cl-和存在的痕量大气有机物对铝的大气腐蚀行为影响.     

Influence of Cr Content on the Corrosion of Fe–Cr Alloys: The Synergistic Effect of NaCl and Water Vapor

The corrosion behavior of pure Fe and Fe–Cr alloys with different Cr content in the presence of a solid NaCl deposit and water vapor at 600°C was studied. Results indicated that the corrosion of pure Fe was severe even in air at 600°C and the scale formed on the surface was compact and uniform. However, with a solid NaCl deposit on its surface, the corrosion of pure iron in air was suppressed to some extent, but the presence of water vapor in the atmosphere causes accelerated corrosion. Under the synergistic effect of NaCl and water vapor, the corrosion of pure iron is accelerated more significantly. In contrast with the known effect of Cr content on the oxidation of Fe–Cr alloys, an increasing Cr content in Fe–Cr alloys increases the corrosion rate of the alloys under the synergistic effect of solid NaCl and water vapor. A mechanism to explain the effect of water vapor and NaCl on the corrosion of pure iron and Fe–Cr alloy is proposed.     

Marine Corrosion and Protection of Aluminum Alloys According to Their Composition and Structure

Based on long-term tests of aluminum alloys in seawater of various climatic zones from the Arctic to the tropics, the peculiarities of their corrosion behavior are revealed. In contrast to other alloys, hydrogen sulfide has a beneficial effect on their corrosion resistance due to the passivation. However, deep in the Black Sea, the alloys, which are susceptible to structural types of corrosion, were subjected to strong exfoliation corrosion, because hydrogen sulfide excluded fouling with microorganisms that inhibits exfoliation corrosion. Alloys of the Al-Mg system exhibit the highest corrosion resistance in seawater. Alloy of an AMr61 type (σ_ul = 340 MPa, σ_0.2 = 180–210 MPa, δ = 11–15%) has shown a good performance. Alloying with scandium and thermomechanical treatment make possible further simultaneous improvement of mechanical properties and corrosion resistance. It is shown that crevice corrosion is more typical of corrosion-resistant low aluminum alloys possessing lower free-corrosion and pitting potentials compared to high alloys, which are susceptible to structural types of corrosion, in particular, exfoliation corrosion. The methods of the aluminum alloys protection against marine corrosion are considered. It is shown that, in contrast to carbon steels, the anodic-cathodic protection is used for aluminum alloys.__________Translated from Zashchita Metallov, Vol. 41, No. 4, 2005, pp. 347–359.Original Russian Text Copyright © 2005 by Sinyavskii, Kalinin.     

On the Mechanism of Intergranular Corrosion of Aluminum Alloys

It is found that intergranular corrosion can proceed on aluminum alloys in either of two forms. The first is characteristic of low-alloy or pure aluminum; it is called crystallographic and is controlled by recrystallization process. High-angle boundaries of growing recrystallized grains accumulate numerous vacancies which partly coagulate. This causes thermodynamical instability of the boundaries, and their electrode potential approaches the potential of active corrosion. The second form characteristic of medium- or high-alloy aluminum is called structure-decomposition and is controlled by peculiarities of the decomposition of supersaturated solid solutions.     

Microstructures and properties of aluminum film and its effect on corrosion resistance of AZ31B substrate

Aluminum films with thickness of 8.78-20.82μm were deposited on the AZ31B magnesium alloys by DC magnetron sputtering.The influences of aluminum film on the micro-mechanical properties and corrosion behavior of the magnesium alloys were investigated.The morphology of aluminum film was examined by scanning electron microscopy and the microstructure of aluminum film was analyzed by X-ray diffiactometry.Nanoindentation and nanoscratch tests were conducted to investigate their micromechanical properties.More...     

超高频脉冲电流作用下纳米Al2O3颗粒对Mg-Gd-Y-Zr合金微弧氧化涂层的影响

目的 进一步提高Mg-Gd-Y-Zr合金微弧氧化涂层的耐腐蚀性能。方法 采用超高频微弧氧化技术在含有Al2O3纳米颗粒的溶液中制备了微弧氧化涂层。利用扫描电子显微镜(FESEM)、能谱仪(EDS)和X射线衍射仪(XRD)对微弧氧化涂层的表面形貌、截面形貌、成分和晶体结构进行分析。利用极化曲线和电化学阻抗谱(EIS)测试了涂层的耐腐蚀性能。结果 频率由0.5 kHz提升至20 kHz后,涂层表面放电孔洞面积由0.07~24.4 μm²降低至0.08~6.3 μm²,涂层的孔隙率由6.47%减小至3.35%。Al2O3纳米颗粒的添加使超高频涂层表面形成大量自封闭孔洞结构,进而进一步降低了涂层表面的孔径面积(0.1~ 4.63 μm²)和孔隙率(0.97%)。极化试验表明,提高频率至20 kHz,涂层的自腐蚀电流密度由4.7×10^‒6 A/cm²降低至4.7×10^‒7 A/cm² ,添加 Al2O3纳米颗粒,涂层的自腐蚀电流密度进一步降低至1.7×10^‒7 A/cm²,表明其耐蚀性能显著提高。阻抗谱显示,20 kHz-Al涂层具有最大的阻抗,说明该工艺可有效提高微弧氧化涂层的耐蚀性能。 结论 超高频可有效降低放电孔洞尺寸,提高微弧氧化涂层的致密性,改善涂层的耐腐蚀性能。超高频与Al2O3纳米粒子的协同作用使涂层表面形成自封闭孔洞结构,进一步提高微弧氧化涂层的致密性和耐腐蚀性能。