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.

Investigation on Fe,Mn,Zn,Cu,Pb and Cd fractions in the natural surface coating samples and surficial sediments in the Songhua River,China

Natural surface coating samples （NSCSs） from the surface of shingles and surficial sediments （SSs） in the Songhua River, China were employed to investigate the relationship between NSCSs and SSs in fractions of heavy metals （Fe, Mn, Zn, Cu, Pb, and Cd） using the modified sequential extraction procedure （MSEP）. The results show that the differences between NSCSs and SSs in Fe fi＇actions were insignificant and Fe was dominantly present as residual phase （76.22% for NSCSs and 80.88% for SSs） and Fe-oxides phase （20.33% for NSCSs and 16.15% for SSs）. Significant variation of Mn distribution patterns between NSCSs and SSs was observed with Mn in NSCSs mainly present in Mn-oxides phase （48.27%） and that in SSs present as residual phase （45.44%）. Zn, Cu, Pb and Cd were found dominantly in residual fractions （〉48%）, and next in solid oxides/hydroxides for Zn, Pb and Cd and in easily oxidizable solids/compounds form for Cu, respectively. The heavy metal distribution patterns implied that Fe/Mn oxides both in NSCSs and SSs were more important sinks for binding and adsorption of Zn, Pb and Cd than organic matter （OM）, and inversely, higher affinity of Cu to OM than Fe/Mn oxides in NSCSs and SSs was obtained. Meanwhile, it was found that the distributions of heavy metals in NSCSs and SSs were similar to each other and the pseudo-total concentrations of Zn, Cu, Pb and Cd in NSCSs were greater than those in SSs, highlighting the more importance for NSCSs than SSs in controlling behaviours of heavy metals in aquatic environments.

Investigation of Adsorption Rates of Pb, Cd, Cu, Co and Ni to Fresh-water Surface Coatings Developed in Nanhu Lake

The adsorption kinetics of five heavy metals onto the natural surface coatings, which were collected in the Nanhu Lake in Changchun, Jilin Province, China, were investigated for the purpose of giving some explanations for the mechanisms of heavy metal adsorption onto the surface coatings with initial metal ions of 5 μmol/L. The results show that firstly, the adsorption of heavy metals onto the surface coatings follows the first order kinetics; secondly, the double-constant rate equation is suitable to describing the adsorption of heavy metals selected onto the natural aquatic surface coatings, following the order K_ Cu>K_ Pb>K_ Co>K_ Ni>K_ Cd; thirdly, there is a significant correlation between the adsorption rate and the physical and chemical characteristics of heavy metals, such as E 0, Δ_fH 0_m, and Δ_fG 0_m based on the linear regression analysis.

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.

铁路客车非金属材料VOCs释放规律试验研究

为了研究温度对铁路客车典型非金属材料中挥发性有机化合物释放量的影响,基于多气固比法和数据拟合法,对典型非金属材料(重防腐涂料、地板布、玻璃纤维增强塑料)的挥发性有机化合物释放规律进行了试验研究.首先,分别测量了4种不同气固比条件下的挥发性有机化合物浓度,得到挥发性有机化合物释放关键参数(初始可散发浓度和分配系数);然后,结合车辆工艺和运用场景,研究不同温度对挥发性有机化合物释放规律的影响.研究结果表明:材质的物理化学性能和温度是影响挥发性有机化合物释放特性的重要因素;温度从16℃升高至55℃,苯系物和醛类散发浓度均呈减小的趋势,重防腐涂料的初始可散发浓度减小为1.8%,其分配系数减小,地板布和玻璃钢的初始可散发浓度减小至0.3%以下,地板布的分配系数增大,玻璃钢的分配系数减小;苯系物是挥发性有机化合物的主要成分,其中以苯乙烯占比最大,甲苯、乙苯以及二甲苯占比排序规律不明显,并且未检测出苯;在铁道车辆烘焙法环保净化处理时,建议重防腐涂料的烘焙温度不小于55℃,地板布和玻璃钢的烘焙温度不小于45℃.

曼尼希碱复合丁香酚基有机硅水性聚氨酯防腐涂层的制备及性能研究

为提升水性聚氨酯(WPU)的耐水及重防腐能力,本文以曼尼希反应合成曼尼希(Mannich)碱缓蚀剂;以4,4′-(1,1,3,3-四甲基二硅氧-1,3-二丙基)双-2-甲氧基苯酚(EUSi)为扩链剂在WPU分子链中引入Si-O-Si等疏水结构,制备有氢键作用的M/EUSiWPU复合涂层。采用核磁共振氢谱、红外光谱分析、乳液稳定性分析对EUSiWPU、曼尼希碱缓蚀剂及复合乳液进行表征、吸水率测试及电化学测试对复合膜和涂层进行性能分析。实验结果初步表明曼尼希碱及EUSiWPU的合成;加入3%曼尼希碱缓蚀剂的M/EUSiWPU-3粒径分布均匀,乳液稳定性强;复合涂层吸水率随缓蚀剂含量增加而降低,最低为19.60%、低频阻抗增强,比EUSiWPU涂层提高近4个数量级;加入曼尼希碱缓蚀剂使涂层自腐蚀电位正向移动,自腐蚀电流先增大后减小,而M/EUSiWPU-3腐蚀速率最低,为5.25×10^(-6) A/cm^(2);自腐蚀电流密度最小,为2.30×10^(-7)μA/cm~2,保护效率达97.56%。

钢桥面铺装体系用环氧重防腐涂料制备与研究

近年来部分工程案例显示环氧富锌涂层在钢桥面防护效果不理想,尤其是在南方沿海的大跨径钢桥面防护中会过早发生腐蚀破坏,主要原因是富锌涂料中的锌粉在高湿热、高温环境下与水气反应而失效,另一方面富锌涂料颜料体积浓度(PVC)高,脆性大,渗透能力弱,在车载压力下容易与基材、中间层滑移等。本文采用韧性环氧树脂、增韧剂、柔性固化剂制备了一种高韧性非锌环氧重防腐涂料,通过拉伸试验、耐热盐水浸泡试验、盐雾试验、高温附着力等方法研究了其力学性能和防腐性能。结果表明,采用聚氨酯增韧改性环氧树脂SLpu、低相对分子质量聚氨酯改性环氧树脂增韧剂Dslu以及复配固化剂[m(聚醚胺固化剂T)∶m(柔性固化剂F)=5∶1]制备的高韧性非锌环氧重防腐涂料拉伸性能、耐盐雾性能和耐热盐水性能优异,尤其是耐热盐水性能远超于环氧富锌涂料,更适合南方沿海高湿环境大跨径钢桥面铺装体系的防护,对解决目前钢桥面防护体系使用寿命不足的问题有一定的参考意义。

ICP-OES与AAS测定门窗幕墙用型材表面涂层中可溶性重金属Pb和Cd

分别采用原子吸收分光光度法(AAS)和电感耦合等离子体发射光谱法(ICP-OES)对门窗幕墙用型材表面涂层中可溶性重金属Pb、Cd的含量进行测定,对方法的检出限、测定下限、准确度和精密度进行分析。结果表明,ICP-OES相较于AAS在准确度、检出限、测定下限和检测效率上有显著优势。ICP-OES在测定铝合金建筑型材表面涂层中可溶性重金属Pb、Cd含量上应用前景广阔。

钢结构重防腐超长配套间隔时间的探讨

以钢结构重防腐涂层配套方案为实验研究对象,确定了中间漆和面漆的具体涂膜厚度,通过中间漆和配套间隔时间的不同,在西北区域的高寒低湿环境下实际模拟了配套间隔时间和拉拔附着力的关系。对设计超长配套间隔时间的工程项目有一定的借鉴和指导作用。

JAS COAT固化剂对磷石膏环境风险的影响

磷石膏是湿法生产磷酸的副产物,大量堆存的磷石膏给环境造成了巨大的压力。通过室内理化性质试验研究了JAS COAT固化剂对磷石膏性能的改良,优选出适宜的JAS COAT固化剂掺量及含水率,并对稳定化机理进行了探讨。结果表明,加水及固化剂不能改变磷石膏中重金属的总量,但明显降低了浸出液中重金属的质量浓度;固化剂掺量为3%~5%时,磷石膏的放射性随含水率增加呈先减小后增大的趋势。