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。     

电镀锌钢材表面物理气相沉积Zn-Mg合金镀层的电化学性能(英文)

锌合金镀层由于具有较强的耐腐蚀性能而得到广泛的关注,特别是Zn-Mg合金镀层,其耐腐蚀性能能得到显著提高。采用气相沉积方法制备不同镁含量的Zn-Mg合金镀层,研究Zn-Mg合金镀层中镁含量对其耐腐蚀性能的影响。在3%NaCl溶液中进行浸泡试验、动电位测试和电偶腐蚀试验,研究不同Mg含量镀层的耐腐蚀性能。结果表明,Zn-Mg合金镀层的耐腐蚀性能与Mg含量显著相关,镀层的腐蚀电位随着Mg含量的增加而降低,但是腐蚀电流密度却升高,直至15%Mg含量;在Zn-Mg合金镀层中存在钝化区。     

Innovation of Ultrafine Structured Alloy Coatings Having Superior Mechanical Properties and High Temperature Corrosion Resistance

High temperature protection requires full coating density, high adhesion, minor oxide inclusions, and preferably fine grains, which is not achievable in most thermal spray processes. High velocity oxygen fuel (HVOF) thermal spray process has been applied extensively for making such coatings with the highest density and adhesion strength, but the existence of not melted or partially melted particles are usually observed in the HVOF coatings because of relatively low flame temperature and short particle resident time in the process. This work has investigated the development of an innovative HVOF process using a liquid state suspension/slurry containing small alloy powders. The advantages of using small particles in a HVOF process include uniform coating, less defective microstructure, higher cohesion and adhesion, full density, lower internal stress, and higher deposition efficiency. Process investigations have proven the benefits of making alloy coatings with full density and high bond strength attributing to increased melting of the small particles and the very high kinetic energy of particles striking on the substrate. High temperature oxidation and hot corrosion tests at 800 °C have demonstrated that the alloy coatings made by novel LS-HVOF process have superior properties to conventional counterpart coatings in terms of oxidation rates and corrosion penetration depths.     

Electrochemical Characteristics in Seawater for Cold Thermal Spray-Coated Al-Mg Alloy Layer

For corrosion protection of carbon steel in a marine environment,cold arc thermal spray coating was applied to the surface with Al and Al-Mg alloy wires.The surface hardness of Al and Al-Mg thermal spray coatings increased with Mg content.And the various electrochemical experiments were carried out to evaluate corrosion damage characteristics of the thermal spray coating layers.The Al and Al-Mg thermal spray coating layers presented negative potentials compared to carbon steel in corrosion potential measurements.And an anodic polarization experiment revealed a tendency of activation polarization with no passivation.Furthermore,the corrosion damage of the thermal spray coating layer in galvanostatic experiment was observed mainly at the defect area,and the Al-3Mg thermal spray coating layer presented less surface damages than others.In addition,the Al-3Mg thermal spray coating layer showed the lowest corrosion rate while having a sufficient driving voltage for cathodic corrosion protection.Therefore,it is an optimal thermal spray material for sacrificial anode.     

耐锌液腐蚀热喷涂涂层的研发现状

生产镀锌板的热浸镀机组中的各种轴承、沉没辊等受锌液的强烈腐蚀,对热镀锌的生产和产品质量有很大影响．热喷涂耐锌液腐蚀涂层是解决这一难题的一种重要的防护方法．本文主要介绍了近年来国内外关于耐锌液腐蚀热喷涂涂层材料的开发及相应的涂层制备技术,系统分析了各涂层材料在锌液中的腐蚀机理和封孔剂在热喷涂涂层耐锌液腐蚀中的重要性,并指...     

Corrosion behaviour of thermal sprayed nitinol coatings

NiTi alloy is here investigated as an alternative coating to stainless steel since it is considered to possess good corrosion properties. Three different thermal spray techniques (high velocity oxy-fuel -HVOF-, vacuum plasma spray -VPS- and atmospheric plasma spray quenching -APS+Q-) have been used for building the coatings, and electrochemical tests have been carried out for corrosion evaluation. Open-circuit tests have revealed that the VPS-coating shows fairly good corrosion resistance, both in the as-sprayed and polished forms. The HVOF coatings however, showed a strong dependence on the surface conditions and APS+Q is dominated by electrolyte penetration through coating cracks, thus exhibiting a higher i_corr.     

热镀锌层在模拟湿热酸性大气环境中的耐蚀性研究

目的研究Q420钢表面热镀锌工艺中,Zn和Zn-Al-Ni-RE合金镀层在酸性铜离子加速盐雾试验条件下的耐蚀性能。方法 Q420钢表面预处理后进行热镀锌,根据GB 6460—1986进行铜加速醋酸盐雾腐蚀试验,对比纯Zn镀层与Zn-Al-Ni-RE合金镀层的耐蚀性。结果 Ni,RE等元素的加入使镀层表面光亮,组织更加细密。在酸性铜离子加速实验进行到192 h时,纯锌镀层的腐蚀质量损失是合金镀层的2.7倍;72 h后纯锌镀层出现红锈,120 h后合金镀层出现红锈,说明Zn-Al-Ni-RE合金镀层比纯Zn镀层更耐腐蚀。结论通过适量添加Al,Ni与稀土元素,能使Q420钢合金镀层的耐蚀性能大幅度提高。     

Anticorrosive performance of repair painting as remedy for deterioration in metallised steel

Abstract

When the various metallic coating systems applied on steel bridges deteriorated, they may need to be repaired by painting because onsite metallic recoating is very difficult. In order to examine the performance of repaired painting on steel plates with the remains of four types of deteriorated metallic coating systems, cyclic corrosion tests were performed in combination with exposure to an acid rain spray. It was found that a residual coating of zinc hot dip galvanising acted as a helpful substrate for the repair painting. Residual coatings of a zinc–aluminium thermal spray and of a zinc–aluminium pseudoalloy did not have such an effect. The residue of an aluminium thermal spray had a positively harmful influence on the repair painting over it. The degree of this influence was correlated with the thickness of the residual coating.     

Investigation of high-performance acid zinc nickel electrolyte

Zinc nickel alloy coatings are increasingly demanded by the automotive industry due to their highly improved corrosion protection over pure zinc and other zinc alloy coatings. To produce zinc nickel coatings with a nickel incorporation of 12 to 16%, mainly alkaline zinc nickel electrolytes are used in the plating industry. Continuous improvements in the field of acidic zinc nickel alloy electrolytes now meet the needs of the automotive industry while being advantageous in specific fields of application.In this paper, zinc nickel coatings deposited from alkaline as well as from ammonium-free acid zinc nickel electrolytes are investigated. The morphology is evaluated by scanning electron microscopy; the texture is investigated by focused ion beam, and X-ray diffraction patterns identify the structure of the coating. The corrosion protection of the zinc nickel coatings and the adhesion of the zinc nickel coatings have been bench-marked. For applications on fasteners, the coefficients of friction have been measured and compared.     

Corrosion Testing of Ni Alloy HVOF Coatings in High Temperature Environments for Biomass Applications

This paper reports the corrosion behavior of Ni alloy coatings deposited by high velocity oxyfuel spraying, and representative boiler substrate alloys in simulated high temperature biomass combustion conditions. Four commercially available oxidation resistant Ni alloy coating materials were selected: NiCrBSiFe, alloy 718, alloy 625, and alloy C-276. These were sprayed onto P91 substrates using a JP5000 spray system. The corrosion performance of the coatings varied when tested at ~525, 625, and 725 °C in K₂SO₄-KCl mixture and gaseous HCl-H₂O-O₂ containing environments. Alloy 625, NiCrBSiFe, and alloy 718 coatings performed better than alloy C-276 coating at 725 °C, which had very little corrosion resistance resulting in degradation similar to uncoated P91. Alloy 625 coatings provided good protection from corrosion at 725 °C, with the performance being comparable to wrought alloy 625, with significantly less attack of the substrate than uncoated P91. Alloy 625 performs best of these coating materials, with an overall ranking at 725 °C as follows: alloy 625 > NiCrBSiFe > alloy 718 ? alloy C-276. Although alloy C-276 coatings performed poorly in the corrosion test environment at 725 °C, at lower temperatures (i.e., below the eutectic temperature of the salt mixture) it outperformed the other coating types studied.     

Enhanced corrosion protection by powder coatings on hot rolled steel (HRS) for high-temperature applications

Hot rolled steel (HRS) has long been a major product to the motor industry for bodywork, as galvanised steel (zinc coatings), and it is widely used in building and as tinplate (including tin and chrome oxide coatings) for food, etc. can-making. Among more specialist uses its moderate production costs makes it suitable for the manufacturing process. In this study, newly developed corrosion protection enhanced silicone based powder coating was evaluated on hot rolled steel (HRS). The powder coating in this study was developed to withstand high temperatures up to 550°C without any degradation. In the study silicone resin was incorporated with fillers, corrosion inhibitors and fibres at various compositions to achieve maximum heat resistance and improved corrosion resistance. Protective behaviours of the differently formulated powder paints were investigated before and after heat exposure. The developed paint system was evaluated using various test methods such as heat resistance, salt spray, Electrochemical Impedance Spectroscopy (EIS), adhesion test and microstructure study using SEM. The evaluation of test results revealed that powder coating combining zinc dust particles and mineral fibres have better performance due to better corrosion and adhesion stability in the corrosive environment before and after heat exposure up to 550°C.     

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.     

High Temperature Corrosion Behavior of Cold Spray Ni-20Cr Coating on Boiler Steel in Molten Salt Environment at 900 °C

Cold spray is an emerging technology that produces high density metallic coatings with low oxide contents and high thermal conductivity, which makes them ideal for high temperature corrosion resistance. In the current investigation, Ni-20Cr alloy powder was deposited on SA 516 boiler steel (0.19C-1.07Mn-0.020S-0.25P-0.010Si-balance Fe) by cold spray process. Oxidation kinetics was established for the uncoated and cold spray Ni-20Cr coated boiler steel in an aggressive environment of Na₂SO₄-60%V₂O₅ at 900 °C for 50 cycles by the weight change technique. X-ray diffraction, FE-SEM/EDAX, and x-ray mapping techniques were used to analyze the oxidation products. Uncoated steel suffered corrosion in the form of intense spalling and peeling of its oxide scale, which may be due to the formation of unprotective Fe₂O₃ oxides. The Ni-20Cr coating was successful in reducing the weight gain of the steel by 87.2% which may be due to the formation of oxides of nickel and chromium.     

A Comparative Study on Ni-Based Coatings Prepared by HVAF,HVOF, and APS Methods for Corrosion Protection Applications

Selection of the thermal spray process is the most important step toward a proper coating solution for a given application as important coating characteristics such as adhesion and microstructure are highly dependent on it. In the present work, a process-microstructure-properties-performance correlation study was performed in order to figure out the main characteristics and corrosion performance of the coatings produced by different thermal spray techniques such as high-velocity air fuel (HVAF), high-velocity oxy fuel (HVOF), and atmospheric plasma spraying (APS). Previously optimized HVOF and APS process parameters were used to deposit Ni, NiCr, and NiAl coatings and compare with HVAF-sprayed coatings with randomly selected process parameters. As the HVAF process presented the best coating characteristics and corrosion behavior, few process parameters such as feed rate and standoff distance (SoD) were investigated to systematically optimize the HVAF coatings in terms of low porosity and high corrosion resistance. The Ni and NiAl coatings with lower porosity and better corrosion behavior were obtained at an average SoD of 300 mm and feed rate of 150 g/min. The NiCr coating sprayed at a SoD of 250 mm and feed rate of 75 g/min showed the highest corrosion resistance among all investigated samples.     

钢结构热喷涂长效防腐蚀技术的研究与发展

综述了热喷涂技术在钢结构长效防腐蚀方面的研究与发展概况。对锌、铝及锌铝合金涂层的耐蚀机理和防护特点作了比较,从国内外对长效防腐蚀涂层的耐蚀性研究、热喷涂防腐蚀材料的开发、防腐蚀喷涂工艺等方面阐述了该项技术的发展,指出了热喷涂长效防腐蚀技术存在的问题并对其发展前景作了展望。     

A new approach to improve high temperature corrosion resistance of thermally sprayed coatings by using electrochemical corrosion tests

In order to increase reliability and lifetime of heat exchangers in waste‐to‐energy plants corrosion resistant thermally sprayed coatings are applied in a higher extent. From the selection of a plant specific spray material and process via laboratory and field experiments up to a successful coating a high amount of time and money is necessary. In particular, experiments in corrosive surroundings at high temperature which are needed to optimize the coating quality are time‐consuming. In order to decrease development times and to reduce costs, corrosion resistance of a thermally sprayed coating under high temperature conditions is compared with its behavior in an aqueous solution. If the high temperature corrosion resistance can be forecast by electrochemical tests, a fast, efficient and cheap possibility to improve the coating quality would be available and the efforts for tests in high temperature environments could be decreased. To accomplish this objective, Diamalloy 1005 was sprayed with the APS‐process on a ferritic steel. Since the performance of thermally sprayed coatings is not only influenced by the coating material but also by the spraying parameters, three different spray parameter sets were used. After analyzing the results of the corrosion tests under high temperature conditions and in aqueous solution an identical assessment of the spray parameter‐specific corrosion protection could be obtained. Ongoing field tests in a waste‐to‐energy plant are expected to prove the laboratory results. So, a first step in the development of a fast, efficient and cheap method to predict the high temperature corrosion resistance of a thermally sprayed coating might have been done.     

电弧喷涂锌基防腐涂层在洞室环境中的耐蚀性研究

采用高速电弧喷涂技术在16MnR钢上制备了Zn和Zn-Al涂层,通过盐雾加速实验考核涂层在5％NaCl溶液中的腐蚀性能,并对涂层腐蚀前后的组织结构进行分析.结果表明,两种Zn基涂层致密,在盐雾实验40 d后未出现红锈,表现出优异的耐腐蚀性能.喷涂纯Zn涂层,其腐蚀产物疏松,对基体主要起到牺牲阳极的保护作用;喷涂Zn-Al涂层,其腐蚀产物致密,起到牺牲阳极和隔离的双重保护作用.     

Characterisation of phosphate coatings obtained using nitric acid free phosphate solution on three steel substrates: An option to simulate TMT rebars surfaces

Phosphate coatings have been obtained on three steel substrates, (a) ferritic-pearlitic (F-P), (b) tempered martensitic (T-M) and (c) tempered martensitic containing oxide scale (T-M-O) at the top to simulate TMT (thermo mechanical treatment) rebar surfaces which are extensively used for composite concrete structure. Nitric acid free phosphate solution was used for the coating purpose. Scanning electron microscopy (SEM), glow discharge optical emission spectrometry (GDOES) and X-ray diffraction (XRD) techniques were used to characterise phosphate coatings. Acicular phosphate microstructure was obtained on T-M-O and T-M steel substrates, whereas coarser phosphate microstructure was obtained on F-P steel substrate. Thinner to thicker coatings were obtained on F-P, T-M and T-M-O steel substrates respectively. Oxide scale, on the T-M-O steel substrate promoted for deposition of phosphate compounds and thereby obtained thickest coating on T-M-O steel substrate. Zinc phosphate (hopeite) on T-M-O steel substrate and zinc phosphate (spencerite) on F-P steel substrate were detected as main phosphate respectively, whereas both zinc phosphates (hopeite and speccerite) on T-M steel substrate were detected in the same proportion. In addition to zinc phosphate, zinc iron phosphate (phosphophyllite) was detected on F-P and T-M steel substrates, whereas iron phosphate (beraunite) was detected on T-M-O steel substrate. A comparative performance against corrosion of all the phosphate coated steel substrates was evaluated by salt spray, Tafel and electrochemical impedance spectroscopy (EIS) studies. Test for extended exposure in open atmosphere as well as simulated highly humid condition were also conducted to identify coating performance. Phosphate coated T-M-O steel substrate showed 4-5 times improved resistance against corrosion than the phosphate coated F-P steel substrate. The bond strength of coated steel substrate with concrete was increased 2-26% for phosphate coating on T-M-O and T-M steel substrates while the same was decreased 4-12% for phosphate coating on F-P steel substrate.     

Zn-Ni合金防腐涂层技术研究进展

Zn-Ni合金涂层技术是近年发展起来的防腐涂层新技术,与锌涂层相比,该涂层具有十分优异的腐蚀防护性能。随着工业的发展,Zn-Ni合金涂层将会成为锌的替代性涂层,在钢铁腐蚀防护领域得到广泛应用,极具发展前景。文中介绍了用电镀、热浸镀、热喷涂和渗镀的方法制备Zn-Ni合金涂层的主要进展情况,讨论了Zn-Ni合金涂层的腐蚀防护机理,指出了今后应把开发Zn-Ni合金基材作为Zn-Ni合金涂层技术获得突破的关键,把开发Zn-Ni复合涂层作为扩大Zn-Ni合金涂层应用的手段,同时应加强对Zn-Ni合金涂层耐腐蚀机理的研究,为Zn-Ni合金涂层技术的研究和应用提供理论指导。     

Effect of fluxing chemical: An option for Zn-5wt.%Al alloy coating on wire surface by single hot dip process

The corrosion of wire is one of the primary causes for premature failure. The ideal way to overcome this problem is to provide corrosion protection right at the time of manufacturing. It is well established fact that Zn-5 wt.% Al alloy coating on steel surface provides much better protection against corrosion than the conventional pure Zn coating. Conventional fluxing operation is done on wire surface using zinc and ammonium chloride mixture before dipping in molten zinc bath. Galvanization bath temperature of about 415 °C for Zn-5 wt.% Al alloy coating on wire surface develops black spots of AlCl₃ when conventional flux is used. Double dip process is being followed for Zn alloy coating on wire surface due to non availability of suitable flux. An effort has been made to develop a suitable flux to obtain Zn-5 wt.% Al alloy coating on wire surface by single hot dip process. A salt mixture (containing zinc, ammonium, sodium, potassium, cobalt and lead chloride) was formulated based on the decomposition temperature of individual chloride salts. Differential thermal and thermo gravimetric analysis indicate the temperatures for complete decomposition of conventional and formulated flux are 445 and 410 °C, respectively. The lower decomposition temperature of formulated flux is ensured black spot free Zn-5 wt.% Al alloy coating. Alloy coated wire consists of alternative layers of zinc rich and aluminium rich phases. The performance of alloy coated wires has been evaluated by salt spray and Tafel tests. The alloy coated wire shows around 4 times improvement of corrosion performance against aggressive chloride environment compared to pure zinc coated wire. This can be attributed to the fact that aluminium rich phase prevents dissolution of zinc rich phase.