Evaluation of the interfacial bonding between fibrous substrate and sputter coated copper

The sputter coatings provide new approaches to the functionalization of textile materials. One of the key issues in the use of sputter coatings onto textiles is the interfacial adhesion between the coated layer and the fiber substrate. The interfacial bonding between polypropylene (PP) fibrous substrate and sputter coated copper was investigated and discussed by abrasion test and peel-off test in this study. It was found that the plasma pretreatment and heating during the sputter coating process obviously improved the adhesion of the coating layer to the PP fibrous substrate. The mechanism of the interfacial adhesion between copper and PP substrate was also examined by atomic force microscopy. The AFM observations revealed the surface and interfacial structures of the PP fibers.     

Discrete layer hydroforming of three-layered tubes

Discrete layer forming proposed in this study is a hydroforming process which can selectively deform the outer tube to a desired shape without any deformation of the inner tube by piercing small holes in the inner tube. A three-layered tube is assembled from inner, middle, and outer tubes, from either similar or dissimilar materials, and deforms simultaneously when internal pressure and axial feed are applied to the tube. In special working environments, multi-layered tubes with combined material properties, high strength, and corrosion resistance are required to satisfy conflicting performance requirements. The feasibility of proposed discrete layer forming process of three-layered tube was evaluated by a tube hydroforming experiment and process analysis was performed. An optimal loading path to prevent wrinkling around holes was developed by an analytical model and was experimentally verified. The results show that the proposed discrete layer forming process can be successfully applicable to hollow forming of non-axisymmetric multilayered tubes for structural purposes.     

Enhancement of Service Life of Steam Generating Tubes in Oil-Fired Boiler for Power Generation Employing Plasma Spray Technology

The effects of Ni-50 mass% Cr alloy coating, that is plasma-sprayed onto the fire-side of steam generating tubes in a heavy oil-fired boiler, on the high temperature corrosion resistance were examined. One of the severe environments in the industrial manufacturing facilities, where thermal sprayed coatings are employed, is the high temperature corrosion such as the oxidation, sulfidation, and low melting fuel ash corrosion in the fire-side of boiler tubes. In the fossil fuel-fired steam generating boiler facilities, the degradation or failure of steam generating tubes that were derived from the contaminants in a lower grade fuel have often occurred. The situation of degradation of the water evaporator and superheater tubes and corrosion-preventing effects of plasma sprayed coating are described. The enhanced effects of plasma sprayed Ni-50 mass% Cr alloy coating for the suppression of hot corrosion failure of the steam generating tubes of boiler are summarized.     

Development of an improved tube galvanizing process by prior metallic coating

Tube galvanizing is a very old and important process industrially. One of the significant process steps in tube galvanizing is the use of flux materials on cleaned tubes for temporary protection before dipping into the liquid zinc bath. However, the fluxing operation is somewhat hazardous and also causes zinc loss by dross and ash generation. An attempt has been made here for the first time to replace fluxing operation by applying a thin metal flash coating on clean tubes prior to galvanizing. The galvanized tubes are then characterized by SEM and EDS to find out the coating thickness and evolved phases. The galvanized tubes are subjected to corrosion tests and coating adhesion tests. The results are very encouraging confirming the presence of desired phases along with excellent corrosion resistance of these tubes.     

Preparation and performance of fluorescent sensing coating for monitoring corrosion of Al alloy 2024

A kind of fluorescent sensing coating was prepared for monitoring corrosion of aluminum alloys by incorporating phenylfluorone（PF） into acrylic paint as sensing material. The fluorescent dye PF reacts with aluminum ions on corroded aluminum substrate to occur fluorescence quenching observed in UV light. This paint system is sensitive tO underlying corrosion processes through reacting with the Al^3＋ produced by anodic reaction accompanying corrosion. After a certain time, when the samples of Al alloy 2024 coated with PF-acrylic paint were immersed in 1 mol/L NaCl solution, fluorescence quenching spots can be seen with unaided eyes. With the development of corrosion process, the size of fluorescence quenching spots increases. Active corrosion areas on the sample surface were found under the fluorescence quenching spots by optical microscope. The corrosion areas can be observed more clearly by SEM, and many pits are found. This suggests that the fluorescence quenching spots are the sites of produced Al^3＋ by the anodic reaction of the local attack of the coated Al alloy substrate in the chloride solution and the corrosion process of the coated AI alloy can be monitored on-line by the sensing coating. The sensitivity of this coating system for detection of anodic reaction associated with corrosion was determined by applying constant charge current and measuring the charge, at which fluorescence quenching is detected in the coating with unaided eyes. Visual observation of coated samples can detect fluorescence change resulting from a charge corresponding to an equivalent hemispherical pit with approximate depth of 50 μn.     

锅炉“四管”用耐磨耐蚀涂层研究进展

总结了锅炉"四管"失效的形式和机理.热腐蚀和高温冲蚀磨损是锅炉"四管"失效的主要原因,采用热喷涂金属涂层、陶瓷涂层及金属陶瓷复合涂层等可以有效控制热腐蚀和高温冲蚀磨损.目前制备高性能涂层常用的方法有等离子喷涂、电弧喷涂、超音速火焰喷涂等.详细介绍了高镍铬合金涂层的研究状况和喷涂工艺的特点,最后展望了纳米结构涂层在该领域的研究进展和应用前景.     

Biodegradation Behavior of Coated As-Extruded Mg–Sr Alloy in Simulated Body Fluid

As-extruded Mg–Sr alloy, a kind of promising biodegradable biomedical material, was coated using micro-arc oxidation and also using a phosphate conversion coating. The corrosion behaviors were investigated using Hanks' solution. The corrosion of the as-extruded Mg–Sr alloy became more serious with increasing immersion time; that is, the corrosion pits became more numerous, larger and deeper. The micro-arc oxidation coating and the phosphate conversion coating were effective in improving the corrosion resistance of the as-extruded Mg–Sr alloy. The micro-arc oxidation coating was much more effective. Moreover, the as-extruded Mg–Sr alloy and the coated as-extruded Mg–Sr alloy exhibited lower corrosion rates than the as-cast Mg–Sr alloy and the corresponding coated as-cast Mg–Sr alloy, indicating that the corrosion properties of the coated samples are dependent on their substrates. The finer microstructure of the substrate of the as-extruded condition corroded much slower. The corrosion resistance of the coated Mg–Sr alloy depended on the coating itself and on the microstructure of the substrate.     

Characterization of metallic textiles deposited by magnetron sputtering and traditional metallic treatments

In this study, the surface appearance, light reflectivity and low-stress mechanical properties of magnetron sputter coated fabric were compared with traditional metallic treated fabrics. It is found that a layer of fine silver particles distributed evenly on the fabric surface with uniform grains and there were no obvious structural damages to the fabric after the sputtering. The sputter coated fabric has a greater value in reflectance and lightness than metallic powder printed fabric, but is lower than that of metallic foil laminated fabric. The values of surface geometrical smoothness (SMD) increased after metallic powder printing while decreasing slightly after sputter coating and decreasing significantly after metallic foil lamination. The tensile loading curves of both sputter coated and untreated cotton spandex fabrics are similar which indicate that the modification of sputter coating is minimal when compared with the other two metallic treatments. Therefore, sputtering has opened up new possibilities in the modification of textile materials and is an exciting prospect for usage in textile design and technical textiles.     

Fe-20Cr溅射纳米涂层的腐蚀电化学性能研究

利用电化学方法与表面分析技术，考察了平面磁控溅射Fe—20Cr纳米涂层的腐蚀电化学性能及耐蚀机制．研究表明，尽管溅射纳米涂层钝化膜的溶解速度高于铸态合金，但其钝化趋势较强，即使在含有0．5mo1／L NaCl的H2SO4溶液中仍能自钝化，而此时铸态合金的钝化趋势非常微弱；纳米涂层的耐点蚀能力也远优于铸态合金；晶粒细化以及铬元素分布均匀性是决定溅射纳米涂层耐点蚀能力的关键因素．     

Radio frequency identification (RFID) based corrosion monitoring sensors Part 2 – Application and testing of coating materials

Cost-effective radio frequency identification (RFID) transponders (tags) were investigated for wireless corrosion monitoring by applying a metal filled conductive composite coating onto the surface of the plastic tags. The coating acted as an electromagnetic interference (EMI) shield by attenuating or completely blocking the radio frequency signals transmitted between the transceiver (reader) and the tag. When the coated RFID tag was exposed to a corrosive environment through accelerated corrosion tests or marine atmospheric tests, the degradation of the coating decreased the EMI shielding effectiveness and resulted in a strengthened communication between the reader and the tag. By establishing a correlation between the corrosion rate of the metal object to be monitored and the sensor responding performance, it was possible to monitor cumulative corrosion damage via wireless sensor reading.     

Eigenschaften und Anwendung von polyurethanbeschichteten Spundwänden

Properties and use of polyurethane coated sheet piling In view of their mechanical and protection properties and in regard of material costs coating of polyurethane elastomers can be considered for the protection of heavy pieces such e.g. sheet piling in underground construction or hydraulic engineering. A comparative study of sprayed polyurethane coatings, tar-modified polyurethanes, tarepoxysystems and epoxy resins shows, that the corrosion behaviour of the coatings is essentially determined by the pretreatment of the base material. In this context, polyurethane spray coatings are characterized one the one hand by high corrosion resistance, on the other hand by their resistance to mechanical damage, high hardness, abrasion resistance and impact resistance, so that even the shipment of shop coated parts has no problems. Welding of coated parts is quite feasible because only local repair of the coating is required afterwards; the surface of the base metal need not be perfectly dry.     

Performance Evaluation of a Commercial Polyurethane Coating in Marine Environment

A material evaluation study has been carried out to determine corrosion behavior of a commercial polyurethane coating system (Souplethane 5) in the marine environment. The coating system is solvent free, two-component polyurethane protective coating. The performance of the coating on steel and rebar concrete was evaluated by conducting different types of tests which include atmospheric exposure, immersion in 5% sodium chloride solution, exposure to splash zone in seawater, salt fog, sabkha soil burial, and electrochemical tests, which include potentiodynamic polarization and AC impedance measurements. Uncoated, coated, and coated scribed specimens were used in each study. In general, the coating showed good corrosion resistance in marine environment. However, the coated samples, when subjected to break under applied compressive load, showed partial or complete detachment from the substrate, e.g., steel and rebar concrete. This appears to be the major drawback of the coating while applying on steel and concrete structures.     

用于燃气锅炉低碳钢耐冲蚀—腐蚀磨损的双层热喷涂层

为防护发电厂锅炉的热交换器管道的腐蚀冲蚀磨损,研究开发了一种热喷涂层涂层（高速火焰喷涂Cr3C2/TiC-25NiCr涂层＋电弧喷Ni21Cr9Mo35Nb涂层）,在锅炉管道上实际应用两年后,对这种双涂层进行冲蚀试验和金相分析,并对其性能进行讨论。结果发现,燃烧电弧喷涂Ni21Cr9Mo3.5Nb涂层在高硫及环境中是一种良好的防护涂层。     

Hot Corrosion Studies of HVOF-Sprayed Coating on T-91 Boiler Tube Steel at Different Operating Temperatures

The aim of the present work is to investigate the usefulness of high velocity oxy fuel-sprayed 75% Cr₃C₂-25% (Ni-20Cr) coating to control hot corrosion of T-91 boiler tube steel at different operating temperatures viz 550, 700, and 850 °C. The deposited coatings on the substrates exhibit nearly uniform, adherent and dense microstructure with porosity less than 2%. Thermogravimetry technique is used to study the high temperature hot corrosion behavior of uncoated and coated samples. The corrosion products of the coating on the substrate are analyzed by using XRD, SEM, and FE-SEM/EDAX to reveal their microstructural and compositional features for the corrosion mechanisms. It is found that the coated specimens have shown minimum weight gain at all the operating temperatures when compared with uncoated T-91 samples. Hence, coating is effective in decreasing the corrosion rate in the given molten salt environment. Oxides and spinels of nickel-chromium may be the reason for successful resistance against hot corrosion.     

Fireside corrosion and ferritic/austenitic steels and high-alloy materials for superheaters,especially reheaters of coal-fired steam generators

In the past the performance of superheater and reheater tubes in coal-fired systems manufactured of ferritic and austenitic steels with respect to high-temperature corrosion has been the subject of various studies. After having adopted the steel X20 CrMo V 12 1 in the sixties the assumption was to have found a high-temperature corrosion resistant material. But already after 60,000 operating hours first tube failures occurred. As a result of the changes in fuel application at the beginning of the sixties interest in solving this problem faded, only to regain significance after the energy crisis. Already more than 20 years ago in England and the United States of America the development of tube materials having an upgraded corrosion resistance had started. Thus, e.g. compound tubes consisting of a creep-resistant tube core made of Incoloy 800 H and a cladding tube of Inconel 671 were introduced. They exhibited excellent characteristics in coal-fired units. Deutsche Babcock AG suggested to install, for test purposes, such a tube in Boiler 14, Unit 3 of Grosskraftwerk Mannheim. The test tube had safe ends of X 20 CrMO V 12 1, thus allowing a direct comparison of the two tube materials. After 22, 000 operating hours the tube was removed for examination. Wall reduction and corrosion damage was found to be extremely small. The paper will discuss this finding and the microstructure modifications in the material.     

Electrodeposition of polypyrrole onto NiTi and the corrosion behaviour of the coated alloy

Polypyrrole (PPy) films were electrodeposited onto nickel--titanium alloy (NiTi) employing sodium bis(2-ethylhexyl) sulfosuccinate (Aerosol OT or AOT) solutions. Polarizing anodically NiTi samples recovered by PPy in a monomer-free solution increases adhesion of the coating. Electrochemical techniques, scanning electron microscopy (SEM) and element analysis were used in determining the corrosion performance of the coated samples in chloride solution. The polymer improves the corrosion performance at the open circuit potential and at potentials where the bare substrate suffers pitting attack. The improvement in both, adhesion and corrosion performance, is discussed considering substrate/polymer interaction, overoxidation of PPy and the role played by AOT.     

Plasma distribution in the slender bore excited by coaxial rf electrode

A metal coaxial radio-frequency (rf) electrode has been utilized to produce plasma and deposit the coating onto the inner wall of the tubes. The inner electrode acts both as a plasma source and as a sputtering target to achieve plasma-based IBAD. The non-uniformity of thickness of deposited films and plasma density in the bore has been investigated for tubes with different lengths and inner diameters. The experimental results demonstrate that plasma density is higher at two ends of the tube and lower in the middle section of the tube. The uniformity of plasma density may increase with the inner diameter of tubes increasing, but will decrease with the length of tubes increasing. Copper films have been deposited using this technique and the variation of film thickness agrees with the distribution of plasma density along the bore axis. It is also observed that the uniformity of plasma density is higher than that of film thickness due to diffusion behavior of plasmas.     

烧结钕铁硼电镀锌铁合金工艺与耐蚀性能

采用弱酸性氯化物镀液在钕铁硼基体上制备了高耐蚀性的锌铁合金镀层,讨论主要工艺参数对镀层铁含量的影响,优化工艺条件。采用盐雾试验(NSS)、SEM和电化学方法研究镀层的耐蚀性能和耐蚀机理。结果表明,优化工艺条件后合金镀层含铁质量分数为0.92%,钝化后在质量分数3.5%的Na Cl溶液中出白锈时间达到196 h。合金镀层对钕铁硼基体起到阳极保护的作用,镀层结晶致密,填补了钕铁硼基体的固有缺陷,同时又为获得致密的钝化膜创造了条件,减少了镀层表面的缺陷,使镀层整体具有极高的电阻,提高了其耐蚀性能。     

Corrosion behaviour of sintered NdFeB deposited with an aluminium coating

A protective, pure Al coating was deposited by direct current (DC) magnetron sputtering onto sintered NdFeB magnets. Separated, single phases of sintered NdFeB (the Nd-rich phase, the B-rich phase and the matrix phase) were prepared by arc melting for open circuit potential (OCP) tests. The corrosion process of the sintered NdFeB magnets coated with Al (Al/NdFeB) was studied experimentally. It was found that the corrosion process can be divided into three different stages. The Al coating cannot provide complete sacrificial protection for the sintered NdFeB magnets.     

Microstructure and corrosion behaviour of Al coating deposited by cold spraying onto FSW AA2219-T87 joint

This work evaluates the microstructure and corrosion behaviour of Al coating deposited by cold spraying onto FSW AA2219 alloy. The results showed that a dense coating could be deposited on the FSW joint surface with low porosity (0.77%). XRD analysis indicated that no new phases were formed during the spraying. Refined grains were observed in the coating as expected by SEM results. Electrochemical tests revealed the coating had positive corrosion resistance performance. Immersion tests confirmed that the coating effectively withstood the corrosion attack in an aggressive environment and a typical intergranular corrosion can be observed in the surface of the coating particles.