IFHANAL-3 Inhibited Chromate-Free Conversion Coatings on V95T2 Aluminum Alloy

Alloys in the Al–Cu–Mg–Zn system are known to be characterized with high corrosion resistance in both atmospheric and aqueous media. It was earlier demonstrated that the alkaline chromate-free converting composite IFHANAL-3 enabled one to produce coatings with protective properties not inferior to those of conventional chromate coatings on a number of aluminum alloys, including that of grade V95 with different thermal treatment. The present work was devoted to studies of the effect of different complexing agents on the oxidation process and protective properties of coatings on V95T2 alloy. The studied modifying dopants decrease the concentrations of different oxides in the composition of conversion coatings, thus facilitating the adsorption of corrosion inhibitors and improvement of their protective properties. The decrease of the oxidation temperature in the solution of IFHANAL-3 modified with inhibitors of the azol type does not ly affect protective properties of the formed coatings.     

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.     

海洋工程用铝合金的腐蚀与防护研究进展

海洋工程用铝合金部件在服役环境下引发的点蚀、晶间腐蚀等已成为困扰机器装备使用寿命和稳定性的关键问题。目前,阴极保护、缓蚀剂、阳极氧化和保护涂层是针对海洋环境中铝合金腐蚀的常用防护措施。阐述了海洋工程装备常用的铝合金类型和使用场所,发现5系和6系铝合金是船舶制造和海洋平台搭建的首选材料,其中,具备优异力学性能、耐腐蚀性能的5系铝合金一般用来制作甲板、储存装置等大型主要承力构件。重点综述了铝合金在海洋大气区、浪花飞溅区、海水全浸区的腐蚀行为和腐蚀机制,经对比发现,与钢不同,铝合金在海水全浸区的腐蚀最严重,而在环境最恶劣的浪花飞溅区腐蚀损伤相对较轻;点蚀、晶间腐蚀是2种典型的铝合金腐蚀类型,同时应力腐蚀、微生物腐蚀也制约着铝合金在海洋工程领域的应用。最后分析了当前在海洋环境中对铝合金腐蚀防护采取的几种措施,指出工程实际中采用的防护方式为2种及2种以上措施的联合使用,并提出铝合金未来在失效行为分析、性能优化和涂层材料选择等方面的发展趋势,以期为研发在极端海洋环境下服役的铝合金及其防护材料提供参考。     

海洋工程用结构铝合金无铬化学转化膜耐腐蚀及涂装配套性能

为改善服役于海洋环境下的结构铝合金的耐腐蚀性及其与底漆的配套性能,在两种典型海洋工程用结构铝合金(5083-H116和6061-T6)基体上制备了一种无铬钛/锆基化学转化膜———Alum-nanoceramic coating。采用扫描电子显微镜(SEM)和能谱仪(EDS)对膜层形貌及组成进行了表征,通过动电位极化曲线和电化学阻抗谱研究了膜层的电化学性能,利用中性盐雾试验及胶带剥离试验分别对膜层耐蚀性及其与环氧厚浆底漆的配套性进行了考察。结果表明:5083和6061铝合金Alum-nanoceramic无铬化学转化膜中性盐雾试验白锈面积达到5%所需时间分别为240h和168h;5083铝合金Alum-nanoceramic膜层比后者显示出更好的与环氧厚浆底漆的配套性能。     

添加剂对铝合金稀土转化膜的影响

目的寻找有效提高稀土转化膜性能的添加剂体系。方法采用电化学手段研究添加剂(硼酸、柠檬酸钠、磷酸钠、硅酸钠、氟化氢铵、氟化钠、草酸铵)对稀土转化膜的影响,对于具有积极作用的添加剂,使用响应面法进行复配,并优化配方。通过扫描电子显微镜(SEM)、能谱仪(EDS)和电化学测试对优化条件下制备的稀土转化膜性能进行表征。结果向基础转化液中加入氟化钠(NaF)、柠檬酸钠(Na_3C_6H_5O_7)和磷酸钠(Na_3PO_4)可以提高稀土转化膜的电化学性能。经过复配并优化配方,得到最优添加剂体系为0.68g/L氟化钠+0.80g/L磷酸钠。该配方可以抑制铝合金在转化液中的溶解,有利于铈元素的沉积,使铈的沉积量由5.01%提高到了9.60%。优化配方下制备出的膜层更加均匀致密,腐蚀电位提高了0.13 V,点滴时间可达122 s。XRD和EDS结果表明,膜层的主要成分为非晶态的铈锰氧化物。结论 0.68 g/L氟化钠+0.80g/L磷酸钠为最优添加剂配方。在优化体系中制得的稀土膜层的电化学性能得到了提升,表面更加均匀致密。     

Corrosion Resistance of Superhydrophobic Mg-Al Layered Double Hydroxide Coatings on Aluminum Alloys

A superhydrophobic surface was successfully constructed to modify the layered double hydroxide (LDH) coatings on aluminum alloy using stearic acid. The characteristics of the coatings were investigated using SEM, XRD, FT-IR and XPS. The corrosion resistance of the prepared coatings was studied using potentiodynamic polarization and electrochemical impedance spectrum. The results revealed that the superhydrophobic surface considerably improved the corrosion-resistant performance of the LDH coatings on the aluminum alloy substrate. The formation mechanism of the superhydrophobic surface was proposed.     

Effect of Al2O3 on the Microhardness of AMg2/Graphite Nanocomposite Powder Gas Dynamic Coatings on Aluminum Alloys

Metal Science and Heat Treatment - Mechanically synthesized hybrid powders of the AMg2/graphite + Al2O3 system and coatings deposited by cold gas dynamic spraying from these powders are studied....     

Characterization of Atmospheric Corrosion of 2A12 Aluminum Alloy in Tropical Marine Environment

In this work, corrosion product formed on 2A12 aluminum (Al) alloy after 3 months of natural exposure in South China Sea atmosphere was characterized by various surface analysis techniques, including scanning electron microscopy, energy-dispersive x-ray analysis, x-ray photoelectron spectroscopy, and x-ray diffraction. The atmospheric corrosion mechanism of Al alloy in marine environment was derived. Results demonstrated that Al alloy specimen experiences serious general corrosion and pitting corrosion. Al and O are enriched in the product film, and Ca and Cl are also found in the film and corrosion pits in Al alloy substrate. The main component compounds existing in the film include Al₂O₃, Al(OH)₃, and AlOOH while AlCl₃ and CaCO₃ are also identified. Al alloy encounters corrosion under tropical marine atmosphere. Although somewhat protective, the formed surface film on Al alloy specimen is attacked by chloride ions, resulting in significant pitting corrosion of Al alloy.     

New Atmospheric Corrosion Inhibitor of D16 Aluminum Alloy

Protection of Metals and Physical Chemistry of Surfaces - Abstract—A mixed corrosion inhibitor (CI), which is an equimolar composition of sodium oleyl sarcosinate (SOS) and sodium...     

Intergranular Corrosion of Cryorolled and Aged D16 Aluminum Alloy

Structural and phase factors influencing the intergranular corrosion (IGC) of D16 aluminum alloy after quenching, isothermal rolling at liquid-nitrogen temperature, and subsequent natural and artificial aging were studied by optical metallography, X-ray diffraction, and transmission and scanning electron microscopy. It is established that the alloy aged at temperatures below 150°C demonstrate low depth and intensity of corrosion attack, which sharply increase with aging temperature up to 190°C. The alloy behavior is caused by the accelerated decomposition of the preliminary supersaturated aluminum solid solution, accompanied by formation of the mixed structure of the matrix with a bimodal distribution of main strengthening phases. It is concluded that IGC of the cryorolled and aged alloy has an equal nature and mainly caused by phase factors.     

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。     

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。     

铝及铝合金在我国的大气腐蚀及其影响因素分析

通过现场暴露试验,得到了十种铝及铝合金在我国七个典型大气环境试验站1年和10年两个周期的大气腐蚀速率;采用灰色关联方法对污染物和气象因素对铝及铝合金短期和长期大气腐蚀速率的影响进行了分析.结果表明:对铝及铝合金大气腐蚀影响最大的污染物因素是SO2,最大的气象因素是最低温度和平均湿度.     

氯化铈对铝合金铬酸盐转化膜防护性能的影响

采用电化学方法研究了6061铝合金在以CeCl3(0～60 mg/L)为添加剂的铬酸盐处理液中所得转化膜的防护性能.极化曲线测试结果表明,加入适量的CeCl3(20～40 mg/L),使电极的腐蚀电位Ecorr和点蚀电位Epit提高很多;电化学阻抗(EIS)测试结果表明,加入CeCl3后,膜层的阻抗大幅度增加.研究表明...     

Cold Spray Al-5% Mg Coatings for the Corrosion Protection of Magnesium Alloys

Poor corrosion resistance is a significant limitation of magnesium alloys as structural materials. To address this problem, the objective of this study was to apply to a magnesium alloy a corrosion-resistant barrier coating that has galvanic compatibility with magnesium and a hardness value no less than that of magnesium. Aluminum coatings were applied to ZE41A-T5 Mg by the cold spray process. A custom-made high-purity Al-5 wt.% Mg powder was produced by spray metal forming for the coating evaluation. In addition, coatings of commercially pure Al (99.5 wt.%), high-purity Al (99.95 wt.%), AA5356, and AA4047 were used for comparison. Coating evaluation included mechanical testing (hardness and adhesion strength) and corrosion testing (salt spray, galvanic coupling, and crevice corrosion). The Al-5% Mg powder resulted in the best overall performance, including a high hardness, 125 H_v100, and an adhesion strength, over 60 MPa, when treated for over 1000 h in a salt spray chamber and with a low galvanic current.     

微弧氧化技术在铝、镁及其合金海洋环境防腐蚀中的应用

分析了海洋腐蚀的特点,对比了微弧氧化膜与几种常用防护膜层的形貌和耐蚀性,研究了微弧氧化膜的绝缘性能及其经喷漆、电泳后的耐蚀性能。结果表明:通过微弧氧化在铝、镁及其合金表面生成具有陶瓷组织的氧化膜,然后进行喷涂或电泳处理,可有效防止点蚀、缝隙腐蚀及电偶腐蚀的发生,是海洋环境中铝、镁合金防腐蚀的一条新途径。     

A study of Corrosion Protection of Aluminum Metal by Tetraethoxysilane Plasma Polymerized Coatings -Influence of Aluminum Surface Pretreatments-

PLASMA polymerization refers to the vacuumdeposition and polymerization process that is caused byreactive species created in a plasma state and also at thesurface exposed to the plasma state.It has manyadvantages for coating or film application[1].Specialadvantages of plasma polymerized(PP)films are asfollows:a thin film of thickness of a few tens ofnanometers to a micrometer can be easily achieved;such films are highly cross-linked and pinhole-free,andhave outstanding barrier characteristic…     

Examination of Aluminum Corrosion Products in Marine or Industrial Marine Atmosphere

A method has been developed to characterize the passivation film formed on aluminum in marine atmosphere, whether polluted or not by sulphur oxides and fluorides The information thus obtained was integrated by X-ray diffractometric analyses. The following corrosion products were found in the marine atmosphere: Al₂O₃· 3H₂O + Al (oxychoride) + Al (hydroxide) (The latter two compounds had not been revealed by X-ray analysis). The corrosion products found in the polluted atmosphere were: AlF₃; Al₂(SO₄)₃ · H₂SO₄; Al₁₁(OH)₃₀Cl₃; AlF_1.96(OH)_1.4; 16Al(OH,F)₃ · 6H₂O; AlF_1.65(OH)_1.35 · H₂O. Since the developed method provides useful quantitative information on the aluminum distribution between the various anions, it is deemed to be a useful tool to study the corrosion kineties and mechanism.     

挤压镁合金腐蚀与防护研究进展

随着挤压镁合金的广泛应用,如何改善其较差的耐蚀性自然成为无可回避的重要研究课题。通过综合分析国内外挤压镁合金腐蚀研究领域的相关研究成果,从腐蚀行为与防护技术两个方面进行了讨论。挤压镁合金易于受到多种腐蚀形式的破坏,其腐蚀行为、性能和机理受到材料特性和腐蚀环境等多种因素的影响,表现出多样性和复杂性,特别是应力和腐蚀协同所用下的挤压镁合金失效行为,尚需开展深入研究。通过优化制备工艺参数、合金化和热处理等技术进行组织和成分优化,基于应力条件、不同的腐蚀环境,开发新型耐腐蚀挤压镁合金,对于提高挤压镁合金抗腐蚀性能,扩大其应用领域具有实用价值。电化学镀、化学转化膜、自修复涂层等涂层技术在合金表面形成钝化膜、陶瓷膜以及释放缓蚀剂,对挤压镁合金提供了有效防护。其中,自修复涂层能够有效解决涂层破损产生的局部腐蚀问题,极大地改善了膜层的防护性能,拥有良好的应用前景,是涂层研发的新方向。     

Au / Ni / Cu 多层薄膜热带海洋气候腐蚀失效机制研究

目的了解Au/Ni/Cu多层金属薄膜在热带海洋气候下的失效机制,为研究电子元器件表面腐蚀失效的早期预警提供参考。方法采用磁控溅射法在p型单晶Si(100)基片上沉积Au/Ni/Cu薄膜,在热带海洋气候环境下进行时效实验,采用原子力显微镜及俄歇电子能谱对薄膜失效表面与界面结构微观变化进行研究。结果时效实验初期,Au/Ni/Cu薄膜表面发生了Au原子聚集,形成了不再连续的岛状结构,岛与岛之间产生了表面微裂纹。随着时效时间的延长,表面形成腐蚀洞,腐蚀洞附近有Ni和Cu扩散至Au层表面。时效时间进一步延长后,腐蚀洞的数量增加,面积增大,此时样品处于腐蚀末期;与此同时,在未产生腐蚀洞的区域,Au/Ni/Cu薄膜界面未出现明显粗化。结论 Au/Ni/Cu薄膜在热带海洋气候中的失效主要是通过表面产生的腐蚀洞进行的。