Corrosion behavior of HVOF Inconel 625 coating in the simulated marine environment

High velocity oxygen fuel(HVOF)spraying process is commonly used to produce superalloy coatings.Inconel 625 coating was prepared on Q235B low carbon steel by HVOF.A series of experiments were conducted to examine the surface and corrosion resistance properties of Inconel 625 HVOF coating.In this paper,potentiodynamic polarization tests and electrochemical impedance spectroscopy(EIS)tests were carried out to evaluate the corrosion resistance of Inconel 625 coating under simulated marine environment.The experiment-al results showed that Inconel 625 coating revealed low porosity and desired coating thickness.Shift in the corrosion potential(E_(corr))to-wards the noble direction combined with much low corrosion current density(i_(corr))indicating a significant improvement of HVOF Inconel 625 coating compared with the substrate.

Root cause of corrosion failure of tin coating on wire clamp in marine atmosphere

The failure cause of a tinned copper wire clamp in marine atmosphere was studied systematically by X-ray photoelectron spectroscopy,scanning electron microscopy with energy dispersive spectroscopy and electrochemical measurements.The main components of the green rust on the surface of the damaged wire clamp are SnO_(2),CuO,Cu_(2)Cl(OH)_(3) and CuCO(OH)_(2).Much of green rust distributes at the platform edge along the axial direction on the crimp connection,and severe corrosion and corrosion pits occur at the platform edge zone along the axial direction.The enriching Cl-at the marine atmosphere and the existing O_(2) in air collectively enhance the corrosion process of the tin coating and the copper matrix.Finite element model results show that the residual stress and strain of the tin coating are the largest at the platform edge along the axial direction on the crimp connection,and the corresponding electrode potential of the tin coating at this zone drops significantly.The above results indicate that the residual strain increases the driving force of the corrosion electrochemical reactions and accelerates the corrosion rate and the pit corrosion of the tin coating at this zone.

Preparation and characterization of controlled-release fertilizers coated with marine polysaccharide derivatives

Encapsulation of water-soluble nitrogen fertilizers by membranes can be used to control the release of nutrients to maximize the fertilization ef fect and reduce environmental pollution.In this research,we formulated a new double-coated controlled-release fertilizer(CRF)by using food-grade microcrystalline wax(MW)and marine polysaccharide derivatives(calcium alginate and chitosan-glutaraldehyde copolymer).The pellets of water-soluble nitrogen fertilizer were coated with the marine polysaccharide derivatives and MW.A convenient and eco-friendly method was used to prepare the CRF.Scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the morphology and composition of the products.The nitrogen-release properties were determined in water using UV-Vis spectrophotometry.The controlled-release properties of the fertilizer were improved dramatically after coating with MW and the marine polysaccharide derivatives.The results show that the double-coated CRFs can release nitrogen in a controlled manner,have excellent controlled-release features,and meet the European Standard for CRFs.

The Behaviour of Superalloys in Marine Gas Turbine Engine Conditions

This paper presents hot corrosion results carried out systematically on the selected nickel based superalloys such as IN 738 LC, GTM-SU-718 and GTM-SU-263 for marine gas turbine engines both at high and low temperatures that represent type I and type II hot corrosion respectively. The results were compared with advanced superalloy under similar conditions in order to understand the characteristics of the selected superalloys. It is observed that the selected superalloys are relatively more resistant to type I and type II hot corrosion when compared to advanced superalloy. In fact, the advanced superalloy is extremely vulnerable to both types of hot corrosion. Subsequently, the relevant reaction mechanisms that are responsible for slow and faster degradation of various superalloys under varied hot corrosion conditions were discussed. Based on the results obtained with different techniques, a degradation mechanism for all the selected superalloys as well as advanced superalloy under both types of hot corrosion conditions was explained. Finally, the necessity as well as developmental efforts with regard to smart corrosion resistant coatings for their effective protection under high temperature conditions was stressed for their enhanced efficiency.

Protection Performance of Plasma Sprayed Al_(2)O_(3)-13 wt%TiO_(2) Coating Sealed with an Organic-inorganic Hybrid Agent

An organic-inorganic hybrid sealing agent was fabricated and used in the plasma sprayed Al_(2)O_(3)-13 wt%TiO_(2)coating,and conventional silicone agent was also used for comparison.Protection performance of the coatings was comprehensively evaluated based on both anti-corrosion and anti-biofouling properties.The results reveal that the sealing treatment is remarkably useful to decrease the porosity of the coating,and the porosity of the coating sealed with the hybrid agent is only 0.035%.Immersion corrosion test and Tafel polarization test reveal that the sealed coating with the hybrid agent exhibits a better corrosion resistance by compared with the coating sealed with silicone agent.The corrosion current density i_(corr) of the hybrid agent sealed coating is only 0.7×10^(-6)A·cm^(-2).Moreover,anti-biofouling tests both in the outdoor analogue hydraulic environment and in the natural marine environment prove that the mentioned novel coating presents a better combination of corrosion resistance and anti-biofouling property by compared with the other coatings,and it could be used as a protection of metal components in the marine environment.

Comparison of electrochemical properties of atmospheric pressure plasma coatings for Al_2O_3-3TiO_2 and CoNiCrAlY in sea water

To improve the durability of underwater rotating products,the corrosion characteristics in harsh marine environment were evaluated through various electrochemical experiments on the Al2O3-3TiO2 and CoNiCrAlY coating layers by atmospheric pressure plasma spray coating process.By evaluating the corrosion resistance of these materials,their applicability to environmentally friendly power generation equipment such as blades of tidal current turbines was examined.According to the Tafel analysis for micro-areas including the coating layer,the coating/metal interlayer and the base metal,the Al2O3-3TiO2 coating layer and the CoNiCrAlY coating layer show markedly lower corrosion current density than the base metal.The corrosion current density of the CoNiCrAlY coating layer (9.75316×10-8A/cm2) is about 1.6 times more than that of the Al2O3-3TiO2 coating layer (6.13139×10-8A/cm2).

Review:Fabrication and Application of Zwitterion-based Functional Coatings

Zwitterion-based materials by virtue of their special physical and chemical characteristics have attracted researchers to utilize them for fabricating functional coatings. The simultaneous presence of positive and negative charges renders the zwitterion-based materials with electrostatically induced hydration properties, which enables a high resistance towards oily pollutants, nonspecific protein adsorption, bacterial adhesion and biofilm formation. This review starts from the working mechanism of zwitterions and covers the fabrication strategies of zwitterion-based functional coatings, namely the zwitterion-bearing binder route, the zwitterion-bearing additive route and the post-generation of coatings containing zwitterionic precursors. The applications of zwitterion-based functional coatings are discussed, including medical implants, marine antifouling and oil-resistant coatings, with focus on the relevant mechanisms of the zwitterion-containing coatings for a specific performance. Finally, some comments and perspectives on the current situation and future development of zwitterion-based functional coatings are given.

Potential Hydrodynamic Performance Enhancement of Hydrokinetic Turbine with Hydrophobic Coatings

Hydrokinetic energy is a promising technology to harness predictable renewable energy from free-flowing water,tides and ocean currents.Many studies have been conducted by researchers and engineers to find out ways to enhance the performance of the hydrokinetic turbine.The current paper reports the experimental study of using hydrophobic coating as an alternative way to improve the performance of hydrokinetic turbine.A hydrophobic coating can lower the friction drag of a surface that is in contact with liquid.For hydrokinetic turbine blade,reduction in friction drag may allow a blade section to have a better lift/drag ratio and have its efficiency improved.In this study,a formula to predict the pattern of drag reduction over a hydrophobic surface has been derived.Two hydrophobic coatings were applied on NACA 63418 hydrofoils and their performances were tested.It was found that NACA 63418 hydrofoil with the hydrophobic coatings had its drag reduced by an average of 3%−4.0%.When the coatings were applied on a 350 mm diameter three-bladed turbine,the maximum increment of rotational speed of the turbine was found to be 2.5%.The performance of the two coatings against marine fouling was also investigated.The weight of plate with and without the coatings increased by 10%and 100%,respectively.

Environmentally friendly expanded graphite-doped ZnO superhydrophobic coating with good corrosion resistance in marine environment

Designing and fabricating the marine anti-corrosion materials without fluorine by superhydrophobic method is a huge challenge. In this study, an environmentally friendly composite coating was prepared by combing modified expanded graphite(EAG) with nano zinc oxide(ZnO). This coating showed superhydrophobic surface and good corrosion resistance. Fourier transform infrared spectroscopy(FITR), X-ray diffraction(XRD),and scanning electron microscopy(SEM) were used to characterize the materials in fabricating process of the coating. The properties of three composite coatings(ZnO,EAG, and EAG@ZnO) were analyzed, including surface roughness, water contact angle, corrosion resistance, selfcleaning and anti-fouling. The combination of ZnO and EAG caused a big water contact angle, leading superhydrophobic surface of the composite coatings. The electrochemical results showed that the superhydrophobic EAG@ZnO coating had a larger capacitive arc diameter and charge transfer resistance, indicating the enhanced anti-corrosion resistance. Meanwhile, the EAG@ZnO coating also showed good self-cleaning and anti-fouling performance according to solid and liquid pollutants tests.In addition, the mechanical properties and stability of the superhydrophobic EAG@ZnO coatings were evaluated by knife peeling and finger scratch tests. In summary, these superhydrophobic and anti-fouling EAG@ZnO composite coatings provide a potential application in marine corrosion and protection field.

丙烯酸硅烷酯柔性自抛光防污涂料制备及性能

以甲基丙烯酸甲酯、丙烯酸丁酯、丙烯酸异辛酯、丙烯酸甲氧基乙酯、丙烯酸三异丙基硅酯为单体,制备了丙烯酸硅烷酯基体树脂,将其与韧性树脂(液态聚丁二烯)共同作为成膜共混树脂,并以Cu_(2)O作为主要防污剂组分、吡啶硫酮铜(CuPT)和代森锌(Zineb)为辅助有机防污剂组分,配制了柔性自抛光防污涂料。对丙烯酸硅烷酯基体树脂进行了FTIR表征和玻璃化转变温度(Tg)测定,对成膜共混树脂进行了SEM测试,对柔性自抛光防污涂料进行了柔韧性、附着力、吸水率和防污性能测试。结果表明,丙烯酸硅烷酯基体树脂的Tg=–20.54℃时,具有较好的物理机械性能;韧性树脂可以作为外增塑手段增加丙烯酸硅烷酯基体树脂的柔韧性,当m(丙烯酸硅烷酯基体树脂)∶m(韧性树脂)=7∶3时,成膜共混树脂的相容性最好;柔性自抛光防污涂料柔韧性为1级,在弹性体基材表面附着力达到4.0 MPa;经过60 d测试,吸水率为1.1%~1.2%;浅海浸泡挂板36个月显示出明显的防污效果。

丙烯酸-环氧树脂涂层对海工混凝土防腐性能的影响

合成了一种丙烯酸-环氧树脂涂层,研究了海水浸泡条件下涂覆丙烯酸-环氧涂层混凝土的力学性能、耐久性能,并对其水化产物及微观结构进行了分析。结果表明:在海水浸泡条件下,相较于无涂层对照组,涂覆丙烯酸-环氧树脂涂层的混凝土抗压、劈裂抗拉强度均相对较高,表面pH值减小幅度较小,抗氯离子渗透性能较好,可以保持混凝土内部的高碱性,水化产物中水化硅酸钙含量相对较高,基体结构致密,孔隙和微裂纹较少。涂覆丙烯酸-环氧树脂涂层可使海工混凝土具有优异的力学性能和耐久性能。

船舶防污减阻涂料研究进展

海洋生物污损引发船体腐蚀加速、寿命缩短、航行阻力增加以及燃料损耗增加等问题,已成为海洋工业的全球性问题。随着人们对海洋环保意识的提高,传统防污涂料释放防污剂的污染问题被日益关注,研究环境友好型防污减阻涂料逐渐成为发展趋势。本文综述了两种防污减阻涂料的研究进展,污损释放型涂料以有机硅和有机氟为研究重点,仿生防污涂料主要研究仿生表面结构与天然活性物质等。本文阐述了现有研究的优缺点及未来研究方向,最后展望了防污减阻涂料的应用前景与发展方向。

东南沿海电厂钢结构涂层失效分析

针对沿海电厂钢结构涂层失效的分析,可为防腐材料选择、防腐方案的制定提供重要依据。利用便携式显微镜观察现役涂层宏观缺陷;利用胶带纸法粉化等级评定、傅里叶变换红外光谱(FT-IR)分析、电化学交流阻抗(EIS)测试判断涂层微观缺陷;利用简化的“接触角测定法”测定涂层表面疏水性。结果表明,涂层存在夹杂气泡破裂和填料脱落导致的孔洞缺陷,涂层/基体的热膨胀系数不匹配导致的裂纹缺陷,碰撞、弯折导致的裂缝缺陷等宏观缺陷;经一定时间暴露后,涂层成膜高分子降解、光老化导致微观缺陷;新涂制涂层材料具有一定的疏水性,经工业海洋大气环境暴露,疏水性迅速下降。由此可得,涂层表面滞留的液态水溶出灰尘中的可溶盐、吸附和吸收大气中的盐微粒和氧气,经涂层缺陷输运至涂层/金属界面,促成钢铁电化学腐蚀发生。涂层/金属界面的腐蚀产物累积,腐蚀产物体积效应导致涂层鼓泡、开裂、剥离,直至涂层完全失效。

热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气环境中的腐蚀行为研究

目的 为详细研究热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气下的腐蚀行为及作用机理,同时为热浸镀Zn-Al-Mg镀层在湿热海洋大气环境中服役提供数据参考。方法 采用腐蚀失重、XRD、SEM、电化学等测试方法对热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气环境下的腐蚀行为进行研究。结果 腐蚀产物主要由Zn_(5)(OH)_(8)Cl_(2)·H_(2)O组成,腐蚀一段时间后,发现少量ZnO、Zn_(5)(OH)_(6)CO_(3),腐蚀产物具有与锌腐蚀类似的层状结构,1 848 h呈“三明治”型,相比于上下两层暗色物质,中层亮色腐蚀产物富集更多的Cl元素。热浸镀Zn-Al-Mg镀层腐蚀速率大体随时间延长呈上升趋势,只在672~840 h腐蚀速率下降,对比镀锌在模拟环境和锌在湿热大气环境中的腐蚀,热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气中表现出较好的耐蚀性。结论热浸镀Zn-Al-Mg镀层在模拟湿热海洋大气下腐蚀产物演变与腐蚀过程中Mg的参与有关。腐蚀672~840h阶段腐蚀速率下降的原因与腐蚀产物中ZnO的减少和Zn_(5)(OH)_(8)Cl_(2)·H_(2)O占比增加有关。对比镀锌在模拟环境和锌在湿热大气环境中的腐蚀,预测热浸镀Zn-Al-Mg镀层在严酷湿热海洋大气中仍具有较高的耐蚀性,可以优先考虑作为湿热海洋环境的建设用材。

改性聚氨酯在海洋防污涂料中的研究进展

由于海洋生物污损对人类造成的危害日益严重,海洋防污成为海洋资源开发中亟待解决的问题,为此,人们探索了许多防污对策。其中,涂覆防污涂料是最经济有效、也是目前应用最广泛的方式。鉴于传统海洋防污涂料对生态环境造成的巨大危害,聚焦绿色、高效、环保型海洋防污涂料,总结了改性聚氨酯在海洋防污方面的发展现况及研究进展。聚氨酯涂料分为溶剂型和水性,2种聚氨酯涂料都具有耐溶剂性等良好特性,水性聚氨酯涂料更加绿色环保,溶剂型聚氨酯涂料具有良好的耐水性,二者都可作为基体树脂用于海洋防污领域,从而减少海洋结构表面的生物污损。通过对聚氨酯涂料进行改性,可以进一步提高其防污性能。对改性聚氨酯在海洋防污涂料中的应用进行了综述,分析了现存问题和改进方案,以期为海洋防污涂料的研发提供参考和建议。

无锡自抛光防污涂料研究进展

海洋污损生物附着问题一直影响海洋运输与海洋工程行业的发展。为减轻海洋生物附着所带来的困扰,防污涂料被广泛应用,而无锡自抛光涂料(TFSPC)因其卓越的防污性能和低毒性而成为防污涂料市场的主流产品。详细探讨了无锡自抛光涂料的工作机理、成分组成以及目前的应用状况。

高低温交替海洋环境下NiCoCrAlY/AlSiY复合涂层的腐蚀失效机理

为探究NiCoCrAlY/AlSiY复合涂层在高低温交替海洋环境中的腐蚀损伤和退化机理,通过设计高-低温氧化交替和高温氧化-酸性盐雾交替试验,对NiCoCrAlY/AlSiY复合涂层腐蚀损伤开展研究。试验结果表明,经750℃高-低温交替氧化50次循环后,涂层在氧化试验中发生氧化侵蚀,但表面结构完整性并未受到破坏。试验结束后合金质量仅增加了3.87 mg/cm^(2),表明涂层有效抑制了氧气向内部发生扩散,避免了基体遭受氧化侵蚀。在50次高温氧化-酸性盐雾交替循环过程中,NiCoCrAlY/AlSiY复合涂层发生了严重的腐蚀降解,试验结束后合金质量高达13.52 mg/cm^(2)。氧化层结构因长期的盐雾侵蚀导致表面松动,萌生腐蚀孔洞甚至发生脱落。随着高温氧化-酸性盐雾交替循环次数的增加,引起涂层损伤的临界反应由氧化侵蚀转变为热腐蚀。混合盐共晶反应生成的氯气作为催化载体,加速了氧化产物的生长,证明NiCoCrAlY/AlSiY复合涂层在高温氧化-酸性盐雾交替环境下的抗腐蚀性能较弱。

海洋防生物污损水凝胶研究进展

综述了国内外对环保型海洋防生物污损涂料水凝胶在海洋防生物污损的应用研究,从水凝胶结构、组成以及自愈合性角度简述了双网络水凝胶、两性离子水凝胶、两亲性水凝胶、自愈合水凝胶的的制备以及国内外对其防污损的应用研究,展望了其未来研究方向。

氮化物涂层在海水环境中磨蚀性能的研究进展

综述了应用于海水环境中不同结构氮化物涂层的磨蚀性能,探讨了基体材料、制备工艺参数、掺杂元素等对氮化物涂层在海水环境中磨蚀性能的影响,分析了氮化物涂层在海水环境中的磨蚀机理,并对氮化物涂层在海水环境中磨蚀性能的研究方向提出了思考与展望。

起落架用高速火焰喷涂WC涂层覆盖高强钢海水环境腐蚀与开裂行为

为探究水陆两栖飞机用起落架材料海洋环境适应性及其失效机制。通过在热轧300M高强钢表面制备高速火焰喷涂WC涂层,使用电化学测试、盐雾实验、拉伸实验、疲劳实验,并通过SEM,EDS,XRD以及CLSM表征,开展其在人工海水环境中的腐蚀行为研究。研究结果表明,在pH值为8.2的人工海水环境中,WC涂层发生明显的钝化,具有较好的耐蚀性,这与在碱性环境下涂层中的Co发生钝化有关。长周期电化学阻抗结果表明,浸泡28天后,涂层耐蚀性上升,这与表面黏结剂形成的氧化物有关。与300M基材相比,喷涂后的材料抗拉强度略微升高,这与涂层内部的残余应力释放有关,其在人工海水中的开裂主要受阳极溶解过程控制。随着预腐蚀时间的增加,材料的疲劳寿命发生明显降低,在预腐蚀过程中,环境中的腐蚀性介质进入涂层内部,增加了缺陷的数量,使得涂层提前发生失效,导致材料断裂敏感性增加。WC涂层有较好的耐蚀性,拉伸过程中残余应力的释放使材料的抗拉强度略微升高,经过预腐蚀后涂层提前发生失效,使得材料疲劳寿命降低。