锌铝涂层的研究开发与应用

锌铝涂层(也叫达克罗涂层)是一种新兴的金属防腐涂覆技术。它具有高耐蚀、无污染、无氢脆等优点。对锌铝涂层的配方、工艺及其应用进行了研究。通过对分散剂、流平剂等的优选,获得了多层片状叠加的致密涂层。通过盐雾试验和酸碱浸泡腐蚀试验比较了锌铝涂层、磷化膜和电镀锌层的性能,表明锌铝涂层是一种优良的耐腐蚀涂层。     

无铬锌铝涂层发展现状

介绍了无铬锌铝涂层(无铬达克罗涂层)制备工艺、耐蚀机理、性能特点及国内外发展现状,对比了无铬锌铝涂层和传统达克罗涂层的特点,指出随着环保要求的提高无铬锌铝涂层将最终取代达克罗涂层。     

石墨烯改性无铬达克罗涂层的组织及耐腐蚀性能

达克罗凭借优异的耐腐蚀性能,广泛应用于汽车、航海、风电等领域,但其所含铬酸盐存在严重的污染问题。采用硅烷偶联剂代替铬酸盐的无铬达克罗解决了污染问题,但相对于达克罗,其硬度低、附着力差、耐腐蚀性较差。通过加入硝酸铈铵和石墨烯对无铬达克罗涂料进行改性,并采用X射线衍射仪、扫描电镜、拉曼光谱仪、快速腐蚀试验、极化曲线试验研究了涂层的物相组成、组织形貌、耐腐蚀性能。结果表明：涂层表面主要是片状锌粉、片状铝粉,致密性好;涂层截面层状堆叠结构清晰。石墨烯添加量为200 mg/L时,改性无铬达克罗涂层的耐腐蚀性能最佳,耐腐蚀时间（5 h）最长,腐蚀电流密度（0.124 μA/cm²）最小,腐蚀电压（-0.82 V）最正。硝酸铈铵通过对金属粉的钝化、粘结作用提高涂层的耐腐蚀性能;石墨烯通过物理屏蔽作用、促进牺牲阳极保护作用提高涂层的耐腐蚀性能。     

电弧喷涂/热扩渗复合工艺改善镁合金耐蚀性能研究

在AZ91D合金表面制备电弧喷涂铝涂层;并在N_2环境下对合金铝涂层表面进行固态扩渗锌处理。利用扫描电镜、能谱分析、浸泡试验等研究手段对喷涂铝涂层及电弧喷涂/扩散锌粉复合涂层形貌、元素分布、相结构及耐腐蚀性能进行研究,并对复合涂层改善基体耐腐蚀性的机理进行分析与讨论。结果表明:AZ91D镁合金铝涂层表面经固态扩渗锌处理后,获得了均匀致密的复合涂层,铝涂层与锌层之间形成了明显的互扩散层,扩散层由外侧的亮白色区和内侧灰褐色区组成;试样在3.5%NaCl溶液中进行浸泡试验表现出了良好的耐腐蚀性能。     

AZ91D镁合金表面电弧喷涂铝锌涂层组织的研究

为了提高AZ91D镁合金的耐腐蚀性能和表面硬度,用电弧喷涂的方法在镁合金表面形成铝锌防护层,并结合扫描电镜和能谱对涂层的组织进行了观察及分析.结果表明,涂层由铝锌两相的机械混合物构成.涂层与基体结合良好,具有较高的显微硬度和较好的抗腐蚀性能.     

铝基金属微粉涂层工艺初探

将铝-锌金属微粉，与磷酸和其它无机金属盐的水溶液、有机或无机还原剂，以及表面活性剂和添加剂，配成为一种水系的金属微粉涂料，涂覆于金属件上经过烧结形成金属基的涂层。试验发现涂层具有金属光泽、较好的附着性和耐腐蚀性，并与达克罗性能进行了比较。同时研究了金属微粉成分、磷酸盐含量对涂层性能的影响。     

镁合金表面电弧喷涂用铝粉芯丝材

为改善镁合金的表面性能，研制了新型铝基粉芯丝材，并采用电弧喷涂的方法在AZ91镁合金表面制备耐蚀涂层。通过盐雾试验和电化学试验对涂层的耐蚀性进行评价。利用光学显微镜和XRD分析技术对涂层的显微组织结构和相组成进行了研究。结果表明，铝基涂层能对镁合金基体起到保护作用，涂层均匀致密；加入Ni和Re能够提高涂层的耐腐蚀性能。     

喷涂金属层长效防腐蚀机理的证明

40多年前,我国开始在淮河闸门上使用喷锌保护钢结构,以后几十年中,喷铝层、先喷锌后喷铝双层工艺均获得应用,最近用大功率二次风喷涂,得到高含铝量的锌铝伪合金长效防腐蚀涂层。中外合作进行了长周期(16000h)中性盐雾加速试验,证明了该防蚀涂层的长效性能。针对美国学者提出的三氧化二铝在涂层背面形成网络,氧化锌颗粒填塞网格,形成耐腐蚀氧化物层,通过扫描电镜试验,分别测出涂层背面的铝、锌和氧化物的含量,证明在背面化学成分中铝和氧化物总原子含量达到70%,因而解释了为什么大功率二次风喷涂的锌铝伪合金耐腐蚀层能够长效。     

热喷涂技术制备铝涂层及其在3.5%NaCl溶液中耐腐蚀性的研究现状

铝是一种应用十分广泛的耐腐蚀材料,热喷涂技术作为表面工程领域的重要技术之一,在钢铁材料表面喷涂铝涂层,能够对钢铁材料起到很好的耐腐蚀保护作用,延长钢铁的使用寿命,减少对钢材的维护与保养。目前通常采用火焰喷涂技术、电弧喷涂技术和冷喷涂技术制备铝涂层,对此三种热喷涂技术制备铝涂层的涂层特点和耐腐蚀性能进行综述。系统归纳了这三种热喷涂技术的热源温度、粒子飞行速度和喷涂距离对形成涂层特点的影响机制,以及铝涂层在3.5%NaCl溶液中的耐腐蚀机理,揭示出铝涂层内部孔隙是影响其耐腐蚀性能的最主要因素,孔隙含量可由孔隙率表示,并指出随着孔隙率的增大,其耐腐蚀性能降低。但是并未详细指出涂层内部孔隙的含量和形状大小对涂层耐腐蚀性能的影响,因此通过进一步优化热喷涂技术制备铝涂层的工艺,研究不同孔隙含量的铝涂层和不同形状大小孔隙的铝涂层在实际服役工况下的具体耐腐蚀程度,对今后热喷涂铝涂层的实际应用具有重要的科学意义,是今后的重点研究方向之一。     

高温高含盐凝析油稳定系统换热器的腐蚀与防护

对模拟高温高含盐腐蚀环境下材料的腐蚀进行了分析,对换热器管束材质和防腐蚀涂层的耐腐蚀性能进行了试验研究。结果表明,纯钛和锌铝共渗防腐蚀技术在腐蚀环境下具有良好的耐腐蚀性能;通过对比两种防腐蚀技术认为选择锌铝共渗涂层防腐蚀技术更为合理。生产中使用效果满意。     

Studies on the Surface Treatment of Aluminium and Zinc

Comparative corrosion and adhesion tests have demonstrated the value of chemical surface treatments for improving the bare corrosion resistance and adhesion of paint to zinc and aluminium. Recent developments have enabled architectural green coatings to be produced on aluminium with consistent colour and chromate-fluoride coatings to be applied on high speed strip lines. It is now possible to correlate the colour of Chromate coatings on zinc with the ratio of the hexavalent chromium to the other anion present; best results are obtained when this anion is sulphate. Yellow Chromate films of very good protective power can be produced from comparatively dilute solutions. Colourless Chromate films can also be obtained from these solutions by adding ammonium sulphate to the processing solution.     

Korrosionsverhalten gespritzter Zink‐Aluminium‐Überzüge in Kurzzeitbewitterungstests

Corrosion behaviour of thermally sprayed zinc‐aluminium‐coatings in short‐term corrosion tests By alloying aluminium to zinc the corrosion resistance can be increased in a multiplicity of media. Thermally sprayed ZnAl 15‐coatings show a higher corrosion resistance than thermally sprayed zinc‐ or hot dip galvanized coatings. This paper presents the results of short term corrosion tests (salt spray test, Kesternich test) with sprayed ZnAl‐coatings with an aluminium content of 2 to 50 M.‐%. The investigations verify very clearly the influence of aluminium on the corrosion behaviour. Depending on the aluminium content the corrosion resistance shows a maximium with a medium content of about 15 or 22 M.‐%.     

Zinc runoff from organically coated galvanised architectural steel

The metallic runoff from the exposed cut-edges of galvanised steel substrates (zinc and an experimental zinc/aluminium alloy) over coated with organic coatings have been quantified over a 30-month period of external exposure. The organic coatings comprised a 200 μm PVC plastisol coating on one side and a 15 μm polyester coating on the other with compatible chromate based pre-treatments and primers. A novel method of increasing cut-edge length per unit area has been developed in which samples are punched with a regular array of holes. This increases the available cut-edge length per unit area by three orders of magnitude over a standard roofing panel. The only measurable leachates detected (>0.5 ppb (part per billion)) over the exposure period have been zinc and iron. All the samples showed significant reduction in zinc runoff upon prolonged exposure with zinc leaching concentrations over a three-month sampling period typically falling from a maximum 1-2 ppm (part per million) upon initial exposure to 0.05-0.1 ppm after 12 months exposure in the harshest industrial and marine sites. Metal ion runoff has been lowest in rural weathering locations (typically 0.5 ppm in a three-month exposure period upon initial exposure falling to <0.05 ppm over the same time period after 12 months exposure).In general at the more severe marine and industrial sites the greatest metal runoff levels were detected from organically coated substrates made from experimental metallic coatings with a 4.95% aluminium, 0.05% magnesium and 95% zinc metallic coating with less runoff leaching from 99.85% zinc coatings. In the former substrate this is due to the presence of subsurface pro-eutectic zinc rich dendrites that are exposed at the cut-edge but are not present in the corrosion resistant aluminium rich surface of the material. In these cases zinc leaching is independent of whether the samples are over-coated with organic layers.     

Metal Coatings on Steel at Lighthouse Beach,Lagos

Abstract

Trials are reported of zinc, lead and aluminium coatings exposed for 8·7 years at Lighthouse Beach, Lagos. Sprayed aluminium coatings gave good results. Zinc coatings applied by hot-dipping or electrodeposition were also successful but, after 8·7 years, sprayed zinc coatings were beginning to fail. Electrodeposited lead coatingscould not be recommended. The thickness of coating applied to the steel specimens was only 50–80 μm.     

Conversion Coatings on Composite Metal Articles

The usual phosphating and chromating methods employed for individual steel, zinc and aluminium differ from one another with regard to treatment time, temperature and specific bath composition. Thus they cannot be used for treating composite metal articles. Zinc phosphate solutions containing only minor amounts of fluoride ions can be used for treating articles where the proportion of aluminium surface, based on the total area, is not greater than about 5%. By increasing the fluoride content a new solution has been developed which permits the production of fine-grained, dense, homogeneous and strongly corrosion-resistant coatings on work-pieces comprising any arbitrary proportion of the total surface area in the form of steel, zinc or aluminium.     

Die Feuerverzinkung siliziumhaltiger Stähle – Problem und Lösungsmöglichkeiten

Hot dip galvanizing of silicon containing steels – the problem and some attempts to its solution Hot dip galvanizing of silicon containing steels, which are increasingly used today, involves the danger of very thick, poorly adherent, unsightly zinc coatings forming on the steel surface. Quite a number of attempts have been made to prevent this drawback. Chemical surface treatments of the steels to be galvanized did not yield the desired success, whilst mechanical surface treatments by shot blasting gave positive results in certain cases only. Galvanizing in the upper temperature range of conventional working practice (475–485 °C) appears appropriate for steels containing 0.15–0.20% Si, whereas low-temperature galvanizing at 430–440 °C using conventional galvanizing baths should be universally applicable provided that suitable methods are found for pre-heating parts of larger dimensions. Galvanizing with inhibited attack of the zinc caused by small additions of aluminium (less than 0.2%) did not yield coating thicknesses independent of the Si content of the steel. High-temperature galvanizing at more than 530 °C gives satisfactory coatings irrespective of the Si content of the steel; saturation of the galvanizing bath with iron should, however, be avoided. Low-temperature galvanizing at less than 430 °C is possible on principle, provided that the melting point of the zinc is reduced by adding alloying elements such as tin (10–30%), magnesium (3%), or aluminium (4–5%). However, tin is expensive, magnesium deteriorates the wetting properties of the steel, and aluminium requires a very careful pre-treatment, the coatings obtained exhibiting low thicknesses and dependency on the Si content of the steel with iron-saturated baths. Galvanizing with reduced zinc concentrations in zinc-saturated lead baths gave zinc coatings independent of the Si content, while currentless galvanizing in zinc-saturated salt baths was not successful.     

层流等离子体射流铝合金表面熔覆层中颗粒分布

采用层流等离子体射流在ZL104铝合金表面制备SiCp／Al-Si复合材料熔覆层。结果表明，熔覆层中SiCp颗粒与基体结合良好，但在熔覆层上颗粒分布不均匀，而且多数分布在枝状晶界上。通过提高层流等离子体射流扫描速度，可以显著提高SiCp颗粒在熔覆层中的均匀性。     

某滨海电厂钢结构腐蚀防护

滨海某电厂4台机组锅炉炉架及其附属钢结构在海洋大气环境中腐蚀严重，其主要腐蚀原因是海洋大气中富含盐分，干湿交替导致金属表面盐浓度较高，水膜中富含氧分子，且溶有其它酸性气体，腐蚀性极强，因而钢结构腐蚀较快。为此提出有机涂层配套体系和热喷锌或喷铝两种解决方案，以确保电厂设施正常安全运行。     

绿色达克罗技术的研究进展

达克罗涂层具有优良的耐蚀性,其工艺简单、无污染,因此被广泛应用于很多防腐领域的基材表面处理.介绍了国内外达克罗技术的发展史,概括了达克罗膜层的性能特点及耐蚀机理,综述了对达克罗涂液主要原材料的研究情况,并指出了该技术存在的一些不足及其今后发展的趋势.     

Zinc‐Aluminium‐Coatings as Corrosion Protection for Steel

An analysis was made to investigate the influence of the alloying of sprayed coatings on the corrosion performance in climates of practical relevance and to evaluate the optimised alloy compositions. Furthermore, the mechanism of corrosion and coating formation was evaluated. The protective effect increased up to an aluminium content of 15 and 22 wt%, respectively, with corrosion rates below 1 µm per year. Electrochemical investigations found a distinctive decrease in the cathodic reaction together with an accumulation of aluminium in per cent and a depletion of zinc. Due to the increasing concentration of aluminium within the layer and the correlated presence of inhibitive corrosion products, the cathodic reaction and therefore the corrosion of the sprayed zinc‐aluminium coatings can be increasingly eliminated.