A Promising Alternative to PEMFC Graphite Bipolar Plates: Surface Modified Type 304 Stainless Steel with TiN Nanoparticles and Elastic Styrene Butadiene Rubber Particles

In order to utilise inexpensive bipolar plates for proton exchange membrane fuel cells (PEMFC), a surface modification with TiN nanoparticles and elastic styrene butadiene rubber (SBR) particles has been applied to the most widely commercialised stainless steel of type 304 which did not satisfy the required properties in the bare form. The electro‐conducting agglomerates were electrophoretically deposited on the stainless steel bipolar plates. The surface modification greatly improved the corrosion resistance of the stainless steel as well as the interfacial contact resistance (ICR). As a result, the cell performance was significantly enhanced and become comparable to that with graphite bipolar plate during operation for 1,000 h. Ac‐impedance results indicated that the TiN–SBR coating was effective not only in reducing the ICR but also in retaining the resistance low throughout the operation. The hydrophobic character of the TiN–SBR coating on the stainless steel bipolar plates, which facilitated the removal of the formed water in the cathode side during the single cell operation, is also responsible for the enhanced cell performance. Therefore, the type 304 stainless steel bipolar plate modified with the electro‐conducting nanosized TiN – elastic SBR particles is suggested to be a promising substituent for the PEMFC graphite bipolar plate.     

Carbon coated stainless steel bipolar plates in polymer electrolyte membrane fuel cells

The desirable properties of the metallic bipolar plates in polymer electrolyte membrane fuel cells (PEMFC) are good corrosion resistance, high electrical conductance, hydrophobicity, and low cost. In this study, carbon films are deposited on stainless steel 316L (SS316L) samples by close field unbalanced magnetron sputtering. The AFM, SEM, and Raman results show that the carbon film is dense, continuous, and amorphous. The corrosion resistance, hydrophobicity, and interfacial contact resistance (ICR) of the carbon coated steel are investigated and compared to those of uncoated SS316L. The deposited carbon film has high chemical inertness thereby significantly enhancing the corrosion resistance of the coated SS316L. Furthermore, the carbon coated SS316L is more hydrophobic and the resulting ICR is elevated to that of graphite. Our results indicate that the properties of the carbon coated SS316L are better than those of conventional graphite bipolar plates.     

Effect of unfunctionalized and HNO3‐functionalized MWCNT on the mechanical and electrical performances of PEMFC bipolar plates

This study aims at developing lightweight and high performance electrically conductive nanocomposites for proton exchange membrane fuel cell (PEMFC) bipolar plates (BPPs). These composites were made from an optimized co‐continuous mixture of Polyethylene terephthalate (PET) and polyvinylidene fluoride (PVDF) reinforced with highly conductive carbon additives composed of carbon black (CB) and synthetic graphite (GR). Multiwall carbon nanotubes (MWCNT) were functionalized then used to improve BPPs electrical conductivity and their mechanical properties, such as flexural and impact strengths. It was observed that the best BPP prototype was obtained using nitric acid (HNO₃)‐functionalized MWCNT. The latter led to the smothest BPP surface, the lowest through‐plane resitivity (0.12 Ω cm) and the highest impact and flexural strengths. These results are attributed to the improved dispersion of the functionalized MWCNT, a result of their best compatibilization with the (PET/PVDF) polymeric phase. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43624.     

Surface conductivity and stability of metallic bipolar plate materials for polymer electrolyte fuel cells

Different types of commercial stainless steels, Ni-based alloys and nitride-coated steels were evaluated as metallic bipolar plate in terms of interfacial contact resistance (ICR) and corrosion resistance in conditions typical of PEFC anode and cathode environments. Results show that stainless steel have a high ICR and undergo corrosion in both anode and cathode. Moreover, although Ni-based alloys showed an ICR comparable with graphite, their behaviour was not satisfactory in corrosive acidic medium. Only nitride-coated stainless steel demonstrated to have low ICR and very good corrosion resistance.     

Nanosized TiN-SBR hybrid coating of stainless steel as bipolar plates for polymer electrolyte membrane fuel cells

In attempt to improve interfacial electrical conductivity of stainless steel for bipolar plates of polymer electrolyte membrane fuel cells, TiN nanoparticles were electrophoretically deposited on the surface of stainless steel with elastic styrene butadiene rubber (SBR) particles. From transmission electron microscopic observation, it was found that the TiN nanoparticles (ca. 50 nm) surrounded the spherical SBR particles (ca. 300-600 nm), forming agglomerates. They were well adhered on the surface of the type 310S stainless steel. With help of elasticity of SBR, the agglomerates were well fitted into the interfacial gap between gas diffusion layer (GDL) and stainless steel bipolar plate, and the interfacial contact resistance (ICR), simultaneously, was successfully reduced. A single cell using the TiN nanoparticles-coated bipolar plates, consequently, showed comparable cell performance with the graphite employing cell at a current density of 0.5 A cm⁻² (12.5 A). Inexpensive TiN nanoparticle-coated type 310S stainless steel bipolar plates would become a possible alternate for the expensive graphite bipolar plates as use in fuel cell applications.     

The effect of plasma‐polymerised silicon hydride‐rich polyhydrogenmethylsiloxane on the adhesion of silicone elastomers

BACKGROUND: Silicone elastomers have outstanding material properties including good thermal stability, low electrical conductivity, biocompatibility and resilient physical and chemical properties. These elastomers, however, exhibit relatively poor adhesion to stainless steel, and the use of a nanometre thick plasma‐polymerised primer layer as a means of enhancing this adhesion was investigated in this study. The primer coatings studied consisted of polyhydrogenmethylsiloxane (PHMS), tetraethyl orthosilicate (TEOS) and mixtures of these two liquid precursors. RESULTS: The plasma‐polymerised primer coatings were deposited onto stainless steel substrates using a PlasmaStream^? atmospheric pressure plasma jet system. Deposited coatings were examined using ellipsometry, contact angle measurements, optical profilometry, Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy and scanning electron microscopy. The adhesion of silicone elastomers bonded to the primed and bare stainless steel surfaces was assessed using 45° adhesion strength measurements. Elastomer adhesion was correlated with surface energy, thickness and roughness. CONCLUSION: An up to 15‐fold increase in adhesive fracture energy was observed for silicone elastomers bonded to the primed versus untreated stainless steel. The highest adhesion was observed for a coating deposited from a PHMS‐to‐TEOS precursor molar ratio of 3 to 1. Copyright © 2009 Society of Chemical Industry     

Tungsten Diffusion Modified AISI 304 Stainless Steel for PEMFC Bipolar Plate

Plasma surface diffusion alloying method has been applied to prepare a tungsten diffusion modified layer on the surface of AISI 304 stainless steel (W‐304 SS). A series of material evaluation experiments were performed on the W‐304 SS specimens to determine whether it is suitable to be used as PEMFC bipolar plate. Results show that the tungsten modified layer (about 2.5 μm in thickness) is mainly composed of tungsten elements. Potentiodynamic and potentiostatic as well as electrochemical impedance spectroscopy measurements in simulated PEMFC operating conditions of 2 ppm F^– and 0.05 M H₂SO₄ solution at 70 °C bubbling with either air or pure H₂, suggest that the corrosion resistance and the passivated behavior of the W‐304 SS are improved. Meanwhile, the interfacial contact resistance (ICR) for the as‐received W‐304 SS reduces considerably, which yields better results than those found in untreated specimens.     

Effect of pore content and pH on the corrosion behavior of hydrophobic ceramic coatings

In this paper, superhydrophobic ceramic coatings were successfully prepared on stainless steel substrates (S304) by sol–gel method, and the effects of pore content and pH conditions on the corrosion resistance of hydrophobic ceramic coatings were studied. As the porosity increases, the contact angle of the coating increases. Among them, the contact angles of the coatings with 15% and 20% porosity in different pH solutions are all greater than 150°, achieving superhydrophobic surfaces. The contact angle results before and after corrosion show that the solution with a higher pH has a greater damage to the hydrophobicity of the coating. The corrosion resistance of the coatings was evaluated comparatively from polarization curves and electrochemical impedance spectroscopy. As the hydrophobicity improves, the corrosion resistance of the hydrophobic ceramic coating is enhanced. The impedance moduli at .01 Hz of the coating are 1.04 × 10³ times (pH 4), .13 × 10³ times (pH 7), and .74 × 10³ times (pH 10) of the bare steel, respectively. With the increase of pH, the corrosion resistance of hydrophobic ceramic coatings decreases, because OH⁻ in the corrosion solution is more easily adsorbed on the surface of the coating, thereby destroying the long hydrophobic chains.     

不锈钢金属双极板TiW和TiTa膜的制备及性能

针对质子交换膜燃料电池金属双极板耐蚀性和导电性有待提高的问题,本文用磁控溅射双靶共溅的方法,在316L不锈钢基体表面沉积TiW和TiTa两种非贵金属膜层。通过X射线衍射、扫描电子显微镜-能谱仪、X射线光电子能谱仪、电化学和接触电阻测试等方法,表征了涂覆膜层后不锈钢的微观结构、表面形貌、化学组成、耐腐蚀性和导电性。实验结果表明,磁控溅射制备得到的TiTa膜表面较为均匀,且TiTa膜沉积的不锈钢具有较好的耐腐蚀性,其恒电位极化电流密度能够维持在0.3μA/cm²;从导电性来看,TiW膜与碳纸之间的接触电阻小于TiTa膜。综合考虑材料的各项性能,认为沉积TiTa膜的316L不锈钢有用作金属双极板材料的潜力。     

Performance Improvement of Wave‐Like PEMFC Stack with Compound Membrane Electrode Assembly

The novel architecture of wave‐like proton exchange membrane fuel cell (PEMFC) stack developed in our previous work achieved peak volumetric power density and specific power of 2,715.9 W L^–1 and 2,157.9 W kg^–1, respectively. However, there still existed perforated bipolar plates and the carbon fiber gas diffusion layer (GDL) was easy to cause damage during the fabrication process of undulate membrane electrode assembles (MEAs). In the present study, sintered stainless steel fiber felt (SSSFF) was employed to work as metallic GDL (MGDL) and bipolar plates simultaneously. Compound membrane electrode assembles (CMEAs) with serpentine and interdigitated flow channels were designed and fabricated using stamping process. A single cell with CMEA was assembled in house and the output performance was evaluated systemically. The results indicated that the peak volumetric power density and specific power of wave‐like PEMFC single with CMEA are 5,764.0 W L^–1 and 4,693.5 W kg^–1 respectively. This study achieved a significant performance improvement due to the concept of CMEA and may propose a possible means to meet the DOE's 2020 technical target that volumetric power density is 2,500 W L^–1 and specific power is 2,000 W kg^–1 for stack.     

UV‐curable sol–gel based protective hybrid coatings

UV‐curable, novel, fluorinated polyether ether ketone urethane acrylate oligomer (FPEEKUA) has been synthesized and used as corrosion‐protector in sol–gel hybrid coatings for metallic substrates. Incorporation of FPEEKUA and sol–gel in the formulations improved coatings’ physical properties such as gel content, hardness, adhesion, gloss, flexibility, and contact angle. Due to strong interaction between acrylate and highly crosslinked structures, mechanical properties improved drastically with homogenously dispersed structures throughout the organic matrix, while water uptake values decreased and thermal stability and char yields increased. Highest contact angle values were measured up to 94° with shinny coatings. The results are important for two reasons. First, polyether ether ketone (PEEK) immiscibility problem are overcome by using reactive oligomer and benefitted from high performance properties of poly(arylene ether ketones) (PAEK)s in hybride coating applications. Second, Coatings combine the advantages of sol–gel with poly(arylene ether ketone urethane acrylate) (PAEKUA) oligomer and they can be used as barrier coatings in metal corrosion protection. Performance tests in corrosive mediums at room temperature of chlorine solution (bleach) for 24 h and also in a 10 wt% HCl solution for 92 h produced promising results for use in corrosion mitigation applications in highly corrosive downstream oil and gas industry. POLYM. ENG. SCI., 59:E146–E154, 2019. © 2018 Society of Plastics Engineers     

Water‐borne melamine–formaldehyde‐cured epoxy–acrylate corrosion resistant coatings

Organic protective coatings are widely used in corrosion control. However, environmental standards establish that the volatile organic compounds either must be removed or controlled at the lowest possible levels. The carcinogenic environmental impact of volatile organic compounds has led to the substitution of solvent‐borne coatings by water‐borne coating systems. Among recently developed water‐borne coatings, epoxy‐ and acrylic‐based coatings have a special significance over other reported water‐borne systems. Keeping in mind, the importance of water‐borne coatings in the present work, we report the synthesis of water‐borne epoxy–acrylate (EpAc) and melamine–formaldehyde (MF) as well as formulation of their anticorrosive coatings. The structural elucidation of MF‐cured EpAc was carried out by FTIR, ¹H NMR, and ¹³C NMR spectroscopic techniques. The coatings of EpAc‐MF were applied on mild steel strips and were evaluated for physicochemical, physicomechanical characterization, and the anticorrosive performance under different environmental conditions. The present coating system EpAc coatings exhibited superior performance as compared to the reported water‐borne epoxy–acrylatecoatings. The presence of melamine–formaldehyde in the resin increases the scratch hardness, impact resistance, alkali resistance, and thermal stability of these coatings. EpAc‐MF‐1 was found to cure at ambient temperature and exhibit good physicomechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Improved mechanical and anticorrosion properties of metal oxide-loaded hybrid sol–gel coatings for mild steel in a saline medium

Abstract

A hybrid organic–inorganic sol–gel coating was successfully prepared and subsequently functionalized individually with five different metal oxide additives. The effect of the incorporated oxides on the corrosion protection performance and scratch-resistance properties of the hybrid base coating on mild steel substrates was investigated using electrochemical techniques, namely electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) as well as mechanical testing. The steel-coated specimens were immersed in 3.5?wt.% NaCl corrosive medium for two weeks and the results reveal an excellent corrosion protection performance by all coating formulations with a significant high corrosion-resistance property for the sample loaded with molybdenum oxide. Scanning electron microscopy (SEM) images proved the absence of corrosion signs, defects, micro cracks, or delamination on the surface of the coated samples. Compared with the pure hybrid coating, all the metal oxide-embedded coatings (except for the sample loaded with yttrium(III) oxide) show comparable aqueous contact angle values as well as enhanced hardness and adherence properties. No noticeable dependence was observed for the surface roughness parameters as a function of the type of incorporated metal oxide within the sol–gel matrix. Overall, the results of this study demonstrate that metal oxides can be advantageous to the desired properties of hybrid sol–gel coatings applied to steel surfaces.     

Effect of trimethylamine borane (TMAB) bath concentration on electrodeposited Ni–B/TiC nanocomposite coatings

In this study, stainless steel material was coated with Ni–B alloy-based, TiC particle reinforced composite film using electrochemical deposition method. The properties of the obtained Ni–B/TiC nanocomposite coatings were investigated in terms of the effect of trimethylamine borane (TMAB) bath concentration, which is a boron source. In addition, the data of pure Ni, Ni–B alloy and stainless steel are presented together for comparison. According to the cyclic voltammogram (CV) analysis, it is seen that TMAB contributes to increasing the deposition rate. In the crystal structure analysis, the effect of TMAB was weaker at low TiC bath concentrations, while the effect of TMAB was more dominant at high TiC bath contents. The crystal grain size values of nanocomposite coatings vary between 5.8 and 16.8 nm, and these values decrease up to 86% when compared to the crystal grain size of the pure Ni coating. Although the increase in TMAB initially causes an increase in the microhardness of nanocomposite coatings, when the TMAB value was further increased, it was observed that the microhardness decreased even more compared to the previous initial value. The highest hardness value was obtained in the sample produced at 5 g/l TiC and 6 g/l TMAB bath contents, and this value was 817 HV. Compared to this value, it was observed that the hardness of pure Ni was 65% lower. It was observed that TMAB did not have significant effect on the coating morphology, but the increase in TMAB caused an increase B content and a decrease in the TiC content in the nanocomposite coating. Furthermore, it was revealed that the increase in TMAB bath concentration caused an improvement on corrosion resistance. The corrosion current of the composite sample with 9 g/l TMAB concentration, which showed the best corrosion performance, decreased by 85% compared to pure nickel.     

Molybdate‐doped copolymer coatings for corrosion prevention of stainless steel

The polypyrrole and polyaniline copolymer coating (PPy‐PAni) and PPy‐PAni doped with sodium molybdate copolymer coating ( ) were synthesized on stainless steel by cyclic voltammetry. The effect of molybdate on the passivation of stainless steel was investigated by linear sweep voltammetry in 0.2 mol L^?1 of oxalic acid. The corrosion prevention performances of these copolymer coatings for stainless steel were investigated by linear sweep voltammetry, electrochemical impedance spectroscopy in 1 mol L^?1 of sulfuric acid, and potentiodynamic polarization in 0.1 mol L^?1 of hydrochloric acid. Copolymer coating doped with molybdate could accelerate the formation of the passive oxide film and have better corrosion prevention efficiencies than PPy‐PAni coating on stainless steel. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40602.     

PTA装置不锈钢材料腐蚀磨损的探讨

采用自制的实验装置,模拟PTA生产装置中回转式干燥机蒸汽列管工作条件,对奥氏体不锈钢0Cr18Ni9(304)、00Cr17Nd4Mo2(316 L)、00Cr19Ni13M03(317 L)和双相不锈钢00Cr22Ni5Mo3N(2205)在含有溴离子和对苯二甲酸颗粒的醋酸介质中,进行腐蚀磨损性能研究。结果表明,4种不锈钢的腐蚀磨损速率随着腐蚀介质温度的升高而增加;在低温时,腐蚀磨损速率差别不大;当温度超过80℃以后,腐蚀磨损性能的差异变大,其中2205的耐腐蚀磨损性能最好,其次为317 L,316 L,而304则最差。相同条件下,腐蚀磨损速率大于均匀腐蚀速率。建议用2205代替316 L制作PTA同转蒸汽管干燥机的加热列管。     

Synergistic effect of silane modified nanocomposites for active corrosion protection

This work presents an effective anticorrosion behavior of a hydrophobic surface on stainless steel 304. The protective coating has been designed by dispersing nanocomposites (cloisite 15A, multiwalled carbon nanotubes and cerium chloride) which act as a corrosion inhibitor. The sol was prepared by using 3-glycidoxypropyltrimethoxysilane (GPTMS), octyltriethoxysilane (OTES) and zirconium (IV) butoxide as precursors. The corrosion resistance of coated stainless steel got improved when nanocomposites were homogeneously embedded in silica sol. The influence of nano-particles on the barrier coatings impedes corrosion. The coatings were analyzed by X-ray diffraction (XRD) to ensure the intercalation and distribution of nanocomposites in layered silicates. Fourier transform infrared spectroscopy (FTIR) was employed to characterize the nanocomposites modified silica sol. Scanning electron microscopy (SEM) was used to examine the morphology of the modified silane coating. The contact angle measurements ensured the hydrophobic behavior of the coatings. The corrosion behavior was investigated using Electrochemical Impedance Spectroscopy (EIS). This study has led to a better understanding of active anticorrosive coatings with embedded nanocomposites and the factors influencing the anticorrosion performance.     

Corrosion protection of AISI 316 stainless steel by ALD alumina/titania nanometric coatings

Stainless steels are used today in a wide range of applications as a result of their combination of high corrosion resistance and good mechanical properties. In some applications, for example, temporary contact biomedical devices or solar water heaters, corrosion resistance may need further improvement, and surface coatings may be applied for enhanced protection. In this study, AISI 316 stainless steel samples with two different standard industrial finishes were coated using atomic layer deposition (ALD) of Al₂O₃/TiO₂ layers. The morphology, composition and corrosion protection was then investigated using different techniques. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were used to obtain a morphological characterization of coatings and substrates. Glow discharge optical emission spectrometry (GDOES) was used to obtain an in-depth profile of composition. Polarization curves in a 0.2 M NaCl solution were used to evaluate the corrosion protection given by the coatings. The deposited ALD layers were found to be almost flawless. The measured RMS roughness values were compared before and after the ALD, and were around 50 and 370 nm for the two samples. GDOES profiles were strongly influenced by the roughness of the substrate. The corrosion protection obtained on AISI 316 stainless steel by the application of nanometric coatings proved to be very effective in reducing the passive region current density from 10^?7 to less than 10^?9 A/cm² and increasing the passive region potential interval from 0.8 to 1.3 V before breakdown.     

35CrMo和00Cr13Ni5Mo硫化氢环境应力腐蚀开裂

用慢应变速率拉伸实验和U形试样浸泡实验、电化学极化技术并结合微观分析手段,在湿硫化氢介质中研究了35CrMo和00Cr13Ni5Mo两种钢的应力腐蚀开裂行为规律。结果表明,35CrMo和00Cr13Ni5Mo钢在实验条件下均具有一定应力腐蚀开裂（SCC）敏感性,其敏感性随着溶液pH的降低和H₂ S浓度的增大而增大;00Cr13Ni5Mo 在实验条件下抗SCC的能力均高于同条件下的35CrMo,在pH3.0的溶液中,二者性能比较接近,在pH4.5的溶液中,00Cr13Ni5Mo 耐H₂S环境SCC的性能明显提高,高于35CrMo,这主要是因为00Cr13Ni5Mo中的耐蚀合金元素增强了其钝化膜的稳定性、降低了氢脆作用所致。     

Modifying a Stainless Steel for PEMFC Bipolar Plates via Electrochemical Nitridation

AISI446 stainless steel was electrochemically nitrided at room temperature. X‐ray photoelectron spectroscopy (XPS) analysis indicated that the nitrided steel was covered with surface ammonia and a layer of nitrides (mainly of mixed chromium nitrides). The nitride layer for 4 h nitrided steel at –0.9 V was about 2.5 nm thick. Dominating oxides appear on the steel's surface, so nitrogen incorporated oxides is a suitable term to describe the nitrided surface. The nitrided surface showed very low interfacial contact resistance (ICR) and excellent corrosion resistance in simulated polymer electrolyte membrane fuel cell (PEMFC) environments. The excellent stability of the nitride steel was confirmed by XPS depth profiling before and after testing in the PEMFC environments. Electrochemical nitridation provides an economic way for modifying the steel's surface to approach the U.S. Department of Energy 2015 goal for bipolar plates.