Preparation technology and anti-corrosion performances of black ceramic coatings formed by micro-arc oxidation on aluminum alloys

In order to prepare ornamental and anti-corrosive coating on aluminum alloys, preparation technology of black micro-arc ceramic coatings on Al alloys in silicate based electrolyte was studied. The influence of content of Na2WO4 and combination additive in solution on the performance of black ceramic coatings was studied; the anticorrosion performances of black ceramic coatings were evaluated through whole-immersion test and electrochemical method in 3.5% NaCl solution at different pH value; SEM and XRD were used to analyze the surface morphology and phase constitutes of the black ceramic coatings. Experimental results indicated that, without combination additives, with the increasing of Na2WO4 content in the electrolyte, ceramic coating became darker and thicker, but the color was not black; after adding combination additive, the coating turned to be black; the black ceramic coating was multi-hole form in surface. There was a small quantity of tungsten existing in the black ceramic coating beside α-Al2O3 phase and β-Al2O3 phase. And aluminum alloy with black ceramic coating exhibited excellent anti-corrosion property in acid, basic and neutral 3.5% NaCl solution.

An electrochemical method for evaluating the resistance to cathodic disbondment of anti-corrosion coatings on buried pipelines

Methods for evaluating the resistance to cathodic disbondment （RCD） of anti-corrosion coatings on buried pipelines were reviewed. It is obvious that these traditional cathodic disbondment tests （CDT） have some disadvantages and the evaluated results are only simple figures and always rely on the subjective experience of the operator. A new electrochemical method for evaluating the RCD of coatings, that is, the potentiostatic evaluation method （PEM）, was developed and studied. During potentiostatic anodic polarization testing, the changes of stable polarization current of specimens before and after cathodic disbonding （CD） were measured, and the degree of cathodic disbondment of the coating was quantitatively evaluated, among which the equivalent cathodic disbonded distance AD was suggested as a parameter for evaluating the RCD. A series of testing parameters of the PEM were determined in these experiments.

Investigation of anti-corrosion property of hybrid coatings fabricated by combining PEC with MAO on pure magnesium

Novel hybrid coatings on pure magnesium were prepared by combining plasma electrolytic carburizing(PEC)with micro-arc oxidation(MAO)to further enhance the anti-corrosion property in this paper.Scanning electron microscopy(SEM)was used to observe the microstructure of the coatings,meanwhile,energy dispersive spectrometry(EDS)and X-ray diffraction(XRD)were separately used to investigate the elemental as well as phase compositions of the coatings.The anti-corrosion property of the coatings was evaluated by potentiodynamic polarization curves as well as electrochemical impedance spectroscopy(EIS).The results show that PEC process is closely related with the effects of adsorption as well as diffusion of the activated carbon atoms,and it can provide a favorable pretreatment surface with predesigned chemical composition to obtain a new kind of phase,namely Si C with superior corrosion resistance and chemical stability,in the following PEC+MAO hybrid coatings.Meanwhile,PEC preprocessing also can afford an excellent micro-structure to increase the coating thickness as well as to improve the compactness of the PEC+MAO hybrid coatings.During the fabrication process of the PEC+MAO hybrid coatings,an overlapping phenomenon in regard to coating thickness can be observed instead of heaping up layer by layer.Compared with both single PEC surface modification layers as well as single MAO coatings,the PEC+MAO hybrid coatings exhibit more superior anti-corrosion property.Especially,the EIS data reveal that the PEC+MAO hybrid coatings can act as an effective protection system to provide relatively excellent long-range anti-corrosion protection.Note also that employing same MAO technique for both single MAO treatment as well as PEC+MAO combining procedure is the key to this research.

Influence of graphene on the anti-corrosion performance of epoxy-based coatings

In this work, graphene-modified epoxy-based anti-corrosion coatings were prepared and the influence of graphene on the anti-corrosion performance of the epoxy-based coatings was investigated with water contact angle test ,chemical solution immersion test, and electrochemical test. The water contact angle and chemical solution resistance of the epoxy-based coatings were improved with an increase in graphene content from 0 to 0.4%. These results prove that addition of graphene can significantly improve the hydrophobicity and impermeability of epoxy- based coatings. However, when the graphene content was increased to 0.5%, the performance of the epoxy-based coatings decreased because of graphene aggregation. Tafel polarization results show that graphene addition can significantly reduce the corrosion current density and corrosion potential of epoxy-based coatings, which enhance their anti-corrosion performance.

The Effect of Cerium Dioxide (CeO_2) in an Anti-corrosion and Self-lubricating Coating

The effect of cerium dioxide(CeO_2)as an additive on the structure and properties of a melting type coating has been studied by means of microhardness measurement,scanning electron microscopy and thermal analysis. The results show that cerium dioxide can modify the microstructure and tribological properties of the coating. Model LIC-23 composite coating which contains CeO_2 performs well as a self-lubricating coating in hydrochloric acid solution.

An Abrasion Resistant TPU/SH-SiO_(2) Superhydrophobic Coating for Anti-Icing and Anti-Corrosion Applications

As a passive anti-icing strategy,properly designed superhydrophobic coatings can demonstrate outstanding performances.However,common preparation strategies for superhydrophobic coatings often lead to environmental pollution,high energy-consumption,high-cost and other undesirable issues.Besides,the durability of superhydrophobic coating also plagues its commercial application.In this paper,we introduced a facile and environment-friendly technique for fabricating abrasion-resistant superhydrophobic surfaces using thermoplastic polyurethane(TPU)and modified SiO_(2)particles(SH-SiO_(2)).Both materials are non-toxicity,low-cost,and commercial available.Our methodology has the following advantages:use of minimal amounts of formulation,take the most streamlined technical route,and no waste material.These advantages make it attractive for industrial applications,and its usage sustainability can be promised.In this study,the mechanical stability of the superhydrophobic surface was evaluated by linear wear test.It is found that the excellent wear resistance of the superhydrophobic coating benefits from the characteristics of raw materials,the preparation strategy,and the special structure.In anti-icing properties test,the TPU/SH-SiO_(2)coating exhibits the repellency to the cold droplets and the ability to extend the freezing time.The electrochemical corrosion measurement shows that the asprepared superhydrophobic surface has excellent corrosion resistance that can provide effective protection for the bare Q235 substrates.These results indicate that the TPU/SH-SiO_(2)coating possesses good abrasion resistance and has great potential in anti-corrosion and anti-icing applications.

A novel anti-corrosion coating for magnesium alloy

A novel enviromental protective water based metallic coating were prepared on the surface of AZ91D magnesium alloy. The properties and structure of the coating were investigated by adhension test, hardness test, heat resisting test, neutral salt spray test and scanning electron microscopy (SEM). The results show that the coating has a stepped structure which can achieve good adhesion of first-grade, heat resistance temperature of 400℃, hardness of HV_ 0.50/30210 and anti-corrosion time of 250h in salt spray test. Meanwhile, the film forming and corrosion mechanism of the coating were also put forward based on the results of the Fourier transform infrared spectroscopy (FTIR) test and electrochemical impedance spectroscopy (EIS) test.

Cerium Methacrylate Assisted Preparation of Highly Thermally Conductive and Anticorrosive Multifunctional Coatings for Heat Conduction Metals Protection

Preparing polymeric coatings with well corrosion resistance and high thermal conductivity(TC)to prolong operational life and ensure service reliability of heat conductive metallic materials has long been a substantive and urgent need while a difficult task.Here we report a multifunctional epoxy composite coating(F-CB/CEP)by synthesizing cerium methacrylate and ingeniously using it as a novel curing agent with corrosion inhibit for epoxy resin and modifier for boron nitride through"cation-π"interaction.The prepared F-CB/CEP coating presents a high TC of 4.29 W m^(−1)K^(−1),which is much higher than other reported anti-corrosion polymer coatings and thereby endowing metal materials coated by this coating with outstanding thermal management performance compared with those coated by pure epoxy coating.Meanwhile,the low-frequency impedance remains at 5.1×10^(11)Ωcm^(2)even after 181 days of immersion in 3.5 wt%NaCl solution.Besides,the coating also exhibits well hydrophobicity,self-cleaning properties,temperature resistance and adhesion.This work provides valuable insights for the preparation of high-performance composite coatings with potential to be used as advanced multifunctional thermal management materials,especially for heat conduction metals protection.

Development of anti-corrosive coating on AZ31 Mg alloy subjected to plasma electrolytic oxidation at sub-zero temperature

Plasma electrolytic oxidation(PEO)is a promising surface treatment to generate adherent and thick anti-corrosive coating on light-weight metals(Al,Mg,Ti,etc.)using an eco-friendly alkaline electrolyte.High energy plasma,however,inevitably generates porous structures that limit their practical performance.The present study proposes a straight-forward simple method by utilizing sub-zero electrolyte(268 K)to alter the plasma characteristics during formation of the protective coating on AZ31 Mg alloy via PEO with a comparison to the electrolyte at room temperature(298 K).In refrigerated electrolyte,the formation of micro-defects is suppressed relatively at the expense of low coating growth,which is measured to be twice lower than that at 298 K due to the temperature-dependent soft plasma discharges contributing to the development of the present coating.As a consequence,corrosion resistance of the sample processed at 268 K is superior to that of 298K,implying that the effect of coating thickness is less dominant than that of compactness.This phenomenon is interpreted in relation to the ionic movement and oxide solidification controlled by soft plasma discharges arising from the temperature gradient between electrolyte and surface of the substrate during PEO.

Bonding strength of graded anti-corrosive coatings of fluoroethylenepropylene (FEP)/polyphenylene sulfide (PPS)

Fluororesin-based anti-corrosive coatings including graded FEP/PPS were prepared on carbon steel by melt powder coating, the bonding strength of all coating systems was determined by the pull-off test. It is found that the poor adhesion of fluororesin coatings to metallic substrates is improved obviously by the graded coating structure of FEP/PPS, and the bonding strength reaches up to 11.8 MPa for the five-layer system. Examination by electron probe microanalysis （EPMA） verifies that the distribution of main components is graded in the five-layer system, which is responsible for the enhancement of the interfacial bonding.

Recent Progress in Superhydrophobic Coatings Using Molecular Dynamics Simulations and Experimental Techniques

Superhydrophobic(SH)coatings are intended to resist a surface from cor­rosion and thereby increases the product life duration.It is also a promising solution to save cleaning costs and time by providing self-clean nature to the surface.This review article provides the most recent updates in design­ing SH surfaces and their characterizations adopted both in experimental and computational techniques.To gain a comprehensive perspective,the SH surfaces present in nature those are inspiring human beings to mimic such surfaces are introduced at the beginning of this article.Subsequently,different fabrication techniques undertaken recently to design artificial SH surfaces are briefly discussed.Recent progress in computations employed in the development of SH surfaces is then discussed.Next,the limitations in SH surfaces are addressed.Finally,perceptiveness of different strategies and their limitations are presented in the concluding remarks and outlook.Overall,this mini review article brings together and highlights the significant advancements in fabrication of superhydrophobic surfaces which may surely help the early-stage researchers/scientists to plan their work accordingly.

CMAS、CMAS+NaVO_(3)、CMAS+海盐作用下热障涂层的腐蚀行为与机理

环境沉积物(CaO-MgO-Al_(2)O_(3)-SiO_(2),CMAS)的高温腐蚀已成为航空发动机涡轮叶片热障涂层过早失效的重要原因之一。然而涡轮叶片工作环境复杂,熔盐、海盐常与CMAS耦合,一起对热障涂层造成多元复杂腐蚀,但目前关于CMAS与盐类的多元耦合腐蚀行为鲜有报道。针对Y2O_(3)部分稳定ZrO_(2)(YSZ)热障涂层在CMAS、CMAS+NaVO_(3)、CMAS+海盐作用下的腐蚀行为进行对比研究。通过XRD、SEM等方法对不同条件下腐蚀后的涂层进行表征,并分析热处理温度、腐蚀物种类对腐蚀行为的影响。结果表明:与CMAS相比,CMAS+NaVO_(3)、CMAS+海盐会在更低的温度下损伤涂层(1200℃)。当三种腐蚀物均能完全熔化时(1250℃),CMAS+NaVO_(3)、CMAS+海盐熔体则由于更大的流动性而大量渗入,腐蚀内部涂层。其中,CMAS+海盐熔体在涂层内的渗透性最强,1250℃热处理4 h后,渗透深度超过400μm。盐类的共存会改变CMAS的性质,增强熔体的渗透能力,增加涂层内部甚至底部失效的倾向。研究结果有助于理解盐类与CMAS耦合时混合熔体对热障涂层的破坏机理及潜在威胁。

Tribological and anti-corrosion performance of epoxy resin composite coatings reinforced with differently sized cubic boron nitride(CBN)particles

A series of high solid content(30 wt%)epoxy resin(EP)composite coatings reinforced with differently sized cubic boron nitride(CBN)particles were fabricated successfully on 304 L stainless steel.Polydopamine(PDA)was used to improve the dispersibility of CBN particles in EP.The structural and morphological features of the CBN particles and the composite coatings were characterized by Raman spectroscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM).Moreover,a UMT-3 tribometer and surface profiler were used to investigate the tribological behaviors of the as-prepared composite coatings.Electrochemical impedance spectroscopy(EIS)and Tafel analysis were used to investigate the coatings'anti-corrosion performance.The results demonstrated that the CBN fillers could effectively enhance the tribological and anti-corrosion properties of the EP composite coatings.In addition,when the additive proportion of the microsized(5μm)and nanosized(550 nm)CBN particles was 1:1,the tribological property of the EP composite coatings was optimal for dry sliding,which was attributed to the load carrying capability of the microsized CBN particles and the toughening effect of the nanosized CBN particles.However,when the additive proportion of the microsized and nanosized CBN particles was 2:1,the tribology and corrosion resistance performance were optimal in seawater conditions.We ascribed this to the load-carrying capacity of the microparticles,which played a more important role under the seawater lubrication condition,and the more compact structure,which improved the electrolyte barrier ability for the composite coatings.

Superior anti-corrosion and self-healing bi-functional polymer composite coatings with polydopamine modified mesoporous silica/graphene oxide

In this article,graphene oxide(GO)and benzotriazole-loaded mesoporous silica nanoparticles(BTA/MSNs)are combined on micro scale through the in situ polymerization of polydopamine(PDA),preparing a selfhealing bi-functional GO(fGO)used as nano-fillers for anti-corrosion enhancement of waterborne epoxy(WEP)coatings.Scanning electronic microscopy(SEM)images show that the BTA/MSNs are uniformly distributed on the surface of high aspect ratio GO nanosheets to endow GO nanocontainer characteristics.UV-vis profiles demonstrate that fGO has p H-controlled release function.Modulus at lowest frequency is generally used for comparing the corrosion resistance of organic coatings.Modulus at lowest frequency(1.42×10^(5)Ωcm^(2))after 30 days immersion in 3.5 wt.%Na Cl solution revealed 2 orders of magnitude higher that of blank WEP(1.17×10^(7)Ωcm^(2)).With artificial cracks on its coatings,fGO/WEP had no obvious rust compared with blank WEP after 240 h of immersion.We anticipate that self-healing and physical barrier bi-functional nanocontainers improve the traditional anticorrosion coating efficiency with better,longer-lasting performance for shipping,oil drilling or bridge maintenance.

Experimental investigation on ablation characteristics of coated and uncoated steel under 30/80 μs impulse current

The ablation tests on coated and uncoated Q235 B steel sheets were conducted under 30/80 μs impulse current simulating the lightning first return stroke current, aimed at further understanding the ablation characteristics of steel and investigating the impact of anti-corrosion coating on these characteristics. Ablation characteristics were investigated through the macroscopic morphology and x-ray diffraction patterns on the surface of damaged zones, the microstructure and micro Vickers hardness on the cross-section of damaged zones, and the maximum rear-face temperature of sample sheets. It can be concluded that the ablation areas of uncoated sheet consist of the melted layer and the heat-affect layer. These ablation areas include not only the area ablated directly by the arc root, of which the depth is deeper, but also the area forming due to the splashing of molten steel, of which the depth is shallower and decreases when the area’s distance from the arc attachment point increases. For coated sheet, coating materials have decomposed and evaporated forming an ablation pit on the sheet surface, in which the steel surface is exposed, and zinc filler of coating primer has infused into the exposed surface. The ablation diameter of uncoated sheet relates to the amplitude of the 30/80 μs impulse current in quadratic function, while for coated sheet, the relation is linear. In general, under the 30/80 μs impulse current, the coating can decrease the energy injected from the arc to the steel sheet and reduce the melting and splashing of steel. As a result, the ablation severity of uncoated sheet is severer than that of coated sheet.

类海胆状TiO_(2)@C微球复合材料高性能钠离子电池负极材料的研究

本工作报道了一种简单且成本低廉的水热方法合成了由碳包覆的高结晶度TiO_(2)纳米棒构成的具有放射状类海胆结构的TiO_(2)@C微米球复合材料(SUL-TiO_(2)@C)钠离子电池负极材料。SUL-TiO_(2)@C表现出多孔的类海胆状结构,由径向生长的金红石纳米棒和包覆其纳米棒的无序碳涂层组成。通过扫描电子显微镜和透射电子显微镜、X射线衍射仪、全自动氮吸附比表面积分析仪、拉曼光谱仪、X射线光电子能谱仪、电化学工作站和电池测试系统对无碳包覆的TiO_(2)(记为SUL-TiO_(2))和SUL-TiO_(2)@C进行表面形貌、晶体结构、比表面积、碳结构、表面元素组成和价态、赝电容行为、循环性能与倍率性能等分析对比,研究结果表明:本项目制备的SUL-TiO_(2)@C复合材料具有更高比例的{110}面、更大的比表面积、更高比例的赝电容贡献、更大的放电比容量和优异的倍率性能。本工作的合成方法为钠离子电池负电极材料研究及未来的应用提供了参考价值和应用价值。

涂塑钢管海水海砂混凝土构件受弯性能研究

将海水海砂混凝土填入涂塑钢管,利用内涂塑层防止氯盐腐蚀钢管,可实现海水海砂混凝土在结构工程中的合理利用,但涂塑层对组合构件力学性能的影响尚不明确。为探究涂塑钢管海水海砂混凝土构件的受弯性能,明晰涂塑层对构件承载变形能力的影响,进行了12根试件的弯曲加载试验,主要参数为海水海砂混凝土强度。研究结果表明,涂塑层对受弯构件破坏形态和受力性能的影响不显著。涂塑钢管海水海砂混凝土受弯构件的破坏形态与传统钢管混凝土的破坏形态相似,均为钢管受压区发生压曲、受拉区达到屈服,核心混凝土产生均匀分布的多条裂缝,整体构件表现出良好的承载能力和变形能力。随着海水海砂混凝土强度的提高,组合构件的受弯承载力随之提高。利用现有钢管混凝土的相关规范可较好地预测涂塑钢管海水海砂混凝土构件的受弯承载力。

环氧涂层钢筋-海砂再生混凝土黏结性能研究

为研究海砂再生混凝土与环氧涂层钢筋间的黏结性能,考虑了不同钢筋类型、混凝土类型、保护层厚度、混凝土强度和锚固长度等因素对黏结性能的影响,对制作的黏结滑移试件进行了中心拉拔试验。结果表明:相同条件下,黏结强度按照普通混凝土、海砂再生混凝土和再生混凝土的顺序依次降低。海砂再生混凝土试件的黏结-滑移曲线与其他试件的相类似,可分为微滑移段、滑移段和下降段。最后,推导出海砂再生混凝土与环氧涂层钢筋间的黏结滑移本构关系表达式,试验值与理论计算值吻合良好,可用于理论分析。

无溶剂环氧涂料在深海环境防腐性能研究与应用

无溶剂环氧涂料有施工简易、防腐性能优异等特点,深海环境服役的环氧涂料目前没有形成统一的防腐性能鉴定标准。通过借鉴熔结环氧粉末(FBE)成熟的评价方法,分析工况需求,研究了一款无溶剂环氧涂料的耐冲击性、孔隙率、弯曲性、湿附着力、阴极剥离、深海适用性等。结果表明:涂料各项性能满足深海环境需求,涂料在海底生产设施特殊管材和不规则部位有较好使用价值,成功应用于南海深水气田海管J型管领(J-collar)的防腐。本文的研究内容和评价方法对于评估深海用环氧涂料,建立相关技术标准有一定的参考价值。

Bio-inspired superhydrophobic magnesium alloy surfaces with active anti-corrosion and self-healing properties

Bio-inspired superhydrophobic magnesium(Mg)alloy surfaces are of increasing interest in corrosion protection due to superior barrier and shielding effects.However,superhydrophobic(SHB)anti-corrosion surfaces are susceptible to damage,which limit their extensive applications.To this end,a micro/nano structure-functional molecule SHB composite coating with self-healing and active anti-corrosion dual-function properties was designed on Mg alloys substrate.The dual-function SHB composite anti-corrosion coating based on lauric acid(La)intercalated and modified hydrotalcite(La-LDH)consisted of three-layer structure,namely La-LDH powder/polydimethylsiloxane(PDMS)/La-LDH film.The anti-corrosion performance of as-prepared coatings was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy(EIS).The results indicate that the SHB coating shows excellent active corrosion resistance.Moreover,we also examined the self-healing and anti-corrosion properties of SHB coating upon physical damage and explained the healing mechanism.After heat treatment,the damaged SHB coating regain its surface microstructure and corrosion protection property.This work expands new insights for the wide application of Mg alloys and the research in the field of metal protection.