Manufacturing Of Bipolar Plates Research Articles

Effect of a PTL Coating and the Clamping Pressure on the Performance of a PEM Electrolyzer Cell

The temperature of the earth is slowly increasing due to the excess CO2 production from the use of fossil fuels in the energy consumption and power production cycles. By 2050, The IEA has devised the net zero energy plan to allow the hydrogen use to extend to several parts of the energy sectors and grow to meet 10% of total final energy consumption by that year [1]. A key player in the decarbonization plan is electrolysis technology. Specifically, PEM electrolysis has gained popularity throughout the years and has started to become more commercialized and its coupling to renewables allowed the technology to produce fully green hydrogen. Researchers’ goal now is to optimize this technology and reduce its cost. As it uses a protonic membrane in an acidic media, it requires expensive components that need to sustain harsh acidic conditions[2].Usually, a PEM water electrolysis unit is made up of a CCM (catalyst coated membrane made with a Nafion 115 coated with iridium oxide on the anode side and nanoparticles of platinum on a carbon support on the cathode side) sandwiched between a titanium porous layer at the anode and a carbon GDL on the cathode. All the components are contained with feeding plates usually made from titanium[3]. The electrolyzer is tightened enough to prevent leaks and ensure a good contact resistance. However, too much clamping can damage the components of the cell as it can reduce the GDL porosity, furthermore can reduce the protonic conductivity of the membrane due to the decreasing of its water content; hence limiting the electrolyzer performance. Another effect is the thinning of the membrane which can affect the hydrogen permeation rate and possibly cause a safety issue as the hydrogen in oxygen content should be less than 2%[4]. Each component has its influence on the contact resistance, the most influential one is that between the porous titanium PTL and the anodic catalytic layer. One uncoated PTL and three coated PTLs (Au, Pt, Ir) where implemented. The precious metal deposit has a positive effect on the interfacial contact resistance between the catalyst layer and the PTL as it decreases compared to an uncoated PTL: the gain is about 150mV at 2A/cm² for a 6.6 MPa clamping pressure – see Fig. 1a. The three deposits lead to the same performances below 2.5A/cm2 and for higher current densities the Iridium deposit is less good than the gold and platinum ones at the beginning of life. After an activation of few hundred hours of operation, the iridium deposit leads to the same performance as the platinum deposit and the gold deposit began to dissolve. To explore higher clamping pressure, the carbon GDL was replaced by a more rigid titanium felt and clamping experiment with an uncoated PTL were performed from 2.9 to 13.22MPa – see figure 1.b. Then decreasing it to see the effect of excessive tightening and relaxation, but unexpected increase in performance was observed up until a certain clamping (6.6MPa) (Fig. 1b) during the relaxation phase then the performances started to decrease. We attribute this behavior to the better water absorption of the membrane during the relaxation phase once the electrical contact is achieved at high pressures. These results might show an efficient method in assembly and clamping of an electrolyzer cell to obtain better performances.[1] F. Dolci, Fuel Cells and Hydrogen Joint Undertaking - Programme review report 2017. 2018.[2] D. G. Bessarabov and P. Millet, PEM water electrolysis. 2017.[3] M. Sánchez-Molina, E. Amores, N. Rojas, and M. Kunowsky, “Additive manufacturing of bipolar plates for hydrogen production in proton exchange membrane water electrolysis cells,” Int. J. Hydrogen Energy, vol. 46, no. 79, pp. 38983–38991, 2021, doi: 10.1016/j.ijhydene.2021.09.152.[4] T. J. Mason, J. Millichamp, P. R. Shearing, and D. J. L. Brett, “A study of the effect of compression on the performance of polymer electrolyte fuel cells using electrochemical impedance spectroscopy and dimensional change analysis,” Int. J. Hydrogen Energy, vol. 38, no. 18, pp. 7414–7422, 2013, doi: 10.1016/j.ijhydene.2013.04.021. Figure 1

Optimization of Filler Compositions of Electrically Conductive Polypropylene Composites for the Manufacturing of Bipolar Plates.

In this research, polypropylene (PP)-graphite composites were prepared using the melt mixing technique in a twin-screw extruder. Graphite, multi-walled carbon nanotubes (MWCNT), carbon black (CB), and expanded graphite (EG) were added to the PP in binary, ternary, and quaternary formations. The graphite was used as a primary filler, and MWCNT, CB, and EG were added to the PP-graphite composites as secondary fillers at different compositions. The secondary filler compositions were considered the control input factors of the optimization study. A full factorial design of the L-27 Orthogonal Array (OA) was used as a Design of Experiment (DOE). The through-plane electrical conductivity and flexural strength were considered the output responses. The experimental data were interpreted via Analysis of Variance (ANOVA) to evaluate the significance of each secondary filler. Furthermore, statistical modeling was performed using response surface methodology (RSM) to predict the properties of the composites as a function of filler composition. The empirical model for the filler formulation demonstrated an average accuracy of 83.9% and 93.4% for predicting the values of electrical conductivity and flexural strength, respectively. This comprehensive experimental study offers potential guidelines for producing electrically conductive thermoplastic composites for the manufacturing of bipolar fuel cell plates.

Characterization of Commercial Polymer–Carbon Composite Bipolar Plates Used in PEM Fuel Cells

Bipolar plates represent a crucial component of the PEM fuel cell stack. Polymer-carbon composites are recognized as state-of-the-art materials for bipolar plate manufacturing, but their use involves a compromise between electrical and heat conductivity, mechanical strength and costs. Thus, all key parameters must be considered when selecting a suitable plate satisfying the demands of the desired application. However, data relevant to commercial materials for such selection are scarce in the open literature. To address this issue, 13 commercially available polymer-carbon composites are characterised in terms of the following parameters: through-plane conductivity, hydrogen permeability, mechanical strength, water uptake, density, water contact angle and chemical stability. None of the materials tested reached the DOE target for electrical conductivity, while five of the materials met the target for flexural strength. The overall best-performing material showed a conductivity value of 50.4 S·cm-1 and flexural strength of 40.1 MPa. The data collected provide important supporting information in selecting the materials most suitable for the desired application. In addition, the key parameters determined for each bipolar plate supply important input parameters for the mathematical modelling of fuel cells.

(Invited) Automated Production of High Performance PEMFC Stacks and Components According to Automotive Requirements

EKPO Fuel Cell GmbH was founded in 2021 by two parent companies, ElringKlinger and Plastic Omnium, whom both are strong and established automotive suppliers with mass manufacturing capabilities and strategic approaches to hydrogen and the fuel cell businesses. The aim of EKPO is the development and production of proton exchange membrane fuel cell stack components and stack modules. Drawing from the experiences of the pilot automated production line since 2016, a fully optimized automated production, with improved production technologies and products, was developed by EKPO in 2021 to achieve an output capability of 10,000 stacks per year. The line was designed with a modular and scalable approach that allows flexibility as well as increased capacity by parallelization. The implementation is successful of producing EKPO’s various stack platforms while maintaining a high level of quality and production standard for the automotive industry.Since EKPO offers a wide range of products, the automated line can cover stack power ranges from 10 kW up to > 200 kW. As a prerequisite for excellent technical performance, in addition to function quality measures were set as key targets from the start of the development. EKPO has thus established consistent and stringent quality process flows and processes for all production steps. These measures include the early involvement of measurability and manufacturability assessment on all process and analysis steps on the different levels (i.e., components and stack). The feedback from each workflow can then continuously improve products, processes, and documentation regarding product specific codes standards and regulations (CSR).The accumulative knowledge from two decades of activity of fuel cell component and stack development enabled EKPO to establish a production range starting from cell and stack components (i.e., bipolar plates, sealings, and plastic end plate modules) to fuel cell stacks and modules produced by fully automated MEA and stack assembly and end-of-line testing. The automated production covers all processes from bipolar plate manufacturing and assembly, CCM and GDL roll good cutting, MEA-assembly, stacking, and the final compression and characterization of the fuel cell stack. The quality matrixes include inspecting performance key figures as well as quality and geometries of the stack and its components. The incoming materials are typically supplied as roll goods, (i.e., GDL, CCM, and metal coil) or as raw material (i.e., plastic granules). As the incoming materials and finished components are very sensitive to environmental conditions and particle contamination, the entire MEA processing and stack assembly process takes place in a cleanroom with controlled climate for maximum process stability and reliability.With a key approach of “design to manufacture” and deep understanding of stack technology and component requirements, EKPO is able to deliver two best in class stacks, namely the NM5 evo and NM12 single and twin platforms.

Multiwalled Carbon Nanotube-Filled Polymer Composites for Direct Injection Molding of Bipolar Plates

Fuel cell bipolar plates are commonly fabricated from graphite, however the associated machining costs are a major limitation to fuel cell commercialization. A promising alternative approach to bipolar plate manufacturing is injection molding of polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of the bipolar plate. In this study, polymer composites based on nylon were injection molded with different weight percentages of conductive filler. Initially, carbon fiber was added to nylon 6,6 at weight percentages ranging from 10 to 50%. Results show that the percolation threshold for carbon fiber in nylon occurs around 25 wt%. Multiwalled carbon nanotubes (MWCNTs) were then added to the direct injection-molded nylon/carbon fiber composites to investigate the synergistic effects of multiple conductive fillers. By introducing carbon nanotubes into the polymer matrix, the nanotubes act as a bridge between the carbon fibers. SEM images show that the MWCNTs fill the void between fibers due to their smaller size and their ease of dispersion. This bridging creates more conductive pathways within the polymer matrix, increasing the electrical conductivity of the composite. Samples with MWCNTs reached conductivities of 64 S/cm, nearing the United States Department of Energy technical target for bipolar plate conductivity (>100 S/cm).

A holistic approach for an intelligent laser beam welding architecture using machine learning for the welding of metallic bipolar plates for polymer electrolyte membrane fuel cells

Laser beam welding is the state-of-the-art technology for joining micro-formed metal foils in the manufacturing of bipolar plates for proton exchange membrane fuel cells. However, the process is limited in the achievable welding speed since humping and undercut effects can occur at high feed rates. These effects significantly reduce the weld seam quality, causing scrap or subsequent failure during operation. As a result, higher manufacturing costs arise and additional quality assurance is needed. In this work, welding experiments, including a photodiode-based sensor system, were conducted on AISI 316L metal foils to evaluate the capability of this sensor for inline and online quality assurance. Based on the results, an intelligent laser beam welding architecture is proposed, representing a holistic approach for a multi-sensor-based and self-improving quality assurance system. The theoretical architecture combines a novel laser beam welding concept with different optical and acoustic sensors for determining the current weld state. It considers sensor data fusion for relevant information on the process behavior via dedicated algorithms applying deep neural networks. The approach is an idea of a predictive weld state determination for a precise and real-time capable weld seam quality assurance.

Additive manufacturing of bipolar plates for hydrogen production in proton exchange membrane water electrolysis cells

Water electrolysis is a process that can produce hydrogen in a clean way when renewable energy sources are used. This allows managing large renewable surpluses and transferring this energy to other sectors, such as industry or transport. Among the electrolytic technologies to produce hydrogen, proton exchange membrane (PEM) electrolysis is a promising alternative. One of the main components of PEM electrolysis cells are the bipolar plates, which are machined with a series of flow distribution channels, largely responsible for their performance and durability. In this work, AISI 316L stainless steel bipolar plates have been built by additive manufacturing (AM), using laser powder bed fusion (PBF-L) technology. These bipolar plates were subjected to ex-situ corrosion tests and assembled in an electrolysis cell to evaluate the polarization curve. Furthermore, the obtained results were compared with bipolar plates manufactured by conventional machining processes (MEC). The obtained experimental results are very similar for both manufacturing methods. This demonstrates the viability of the PBF-L technology to produce metal bipolar plates for PEM electrolyzers and opens the possibilities to design new and more complex flow distribution channels and to test these designs in initial phases before scaling them to larger surfaces.

Injection Molding of Electrically-Conductive Polymer Composite Bipolar Plates

Bipolar plates are commonly fabricated from graphite, however the associated machining costs are a major limitation to fuel cell commercialization. In addition, graphitic bipolar plates comprise up to 80% of the weight of a fuel cell. Here we propose an alternative approach to bipolar plate manufacturing: injection molding of electrically-conductive polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of the bipolar plate. Prior efforts to injection mold polymer composites for fuel cell bipolar plates have resulted in electrical conductivities that do not meet the United States DOE technical targets for bipolar plate conductivity (> 100 S/cm) [1-3]. In efforts to achieve higher conductivities, Hwang et al. compression molded carbon fiber epoxy composites [4]. While compression molding can be used for production of high volumes, injection molding is most ideal for the levels of mass production required for full-scale commercialization of fuel cells. For this reason, we will be investigating the suitability of injection molding polymer composites with sufficient electrical conductivities.In this work, carbon fiber and carbon nanotubes were added to nylon at varying weight percentages. The conductivity of carbon fiber-filled composites ranged from 10 – 20 S/cm. High carbon fiber loadings increased conductivity, however beyond 50 wt%, the increased viscosity of the polymer blends can inhibit proper injection molding. Carbon nanotubes were then added to these composites to investigate the synergistic effects of adding conductive fillers with different aspect ratios. These samples reached conductivities up to 65 S/cm, rising closer to the US DOE technical target. In efforts to achieve higher conductivities, nickel-coated carbon fibers were added to nylon. The conductivities of these samples were above the US DOE target, reaching 150 S/cm. Interestingly, the addition of carbon nanotubes to these composites did not increase conductivity. If successful in a fuel cell, these polymer composites may provide a pathway to cheaper, lighter fuel cells with higher specific energies. Dweiri, R.; Sahari, J., Electrical properties of carbon-based polypropylene composites for bipolar plates in polymer electrolyte membrane fuel cell (PEMFC). Journal of Power Sources 2007, 171 (2), 424-432.Wu, M.; Shaw, L. L., On the improved properties of injection-molded, carbon nanotube-filled PET/PVDF blends. Journal of Power Sources 2004, 136 (1), 37-44.Mighri, F.; Huneault, M. A.; Champagne, M. F., Electrically conductive thermoplastic blends for injection and compression molding of bipolar plates in the fuel cell application. Polymer Engineering and Science 2004, 44 (9), 1755-1765.Hwang, I. U.; Yu, H. N.; Kim, S. S.; Lee, D. G.; Suh, J. D.; Lee, S. H.; Ahn, B. K.; Kim, S. H.; Lim, T. W., Bipolar plate made of carbon fiber epoxy composite for polymer electrolyte membrane fuel cells. Journal of Power Sources 2008, 184 (1), 90-94. Figure 1

Evaluating Current Distribution and Influence of Defect Sites for Graphitic Compound Bipolar Plate Materials

AbstractWith the growth in power and size of energy conversion devices, the consideration of current distribution inside cells and stacks becomes increasingly important. In light of understanding the effect of the material properties of graphitic compound materials on current distribution, we developed a novel measurement cell based on a segmented current feed and a segmented measurement board. Using this cell, we determined the cross‐conduction of current in three commercial graphitic compound materials used for the manufacturing of bipolar plates. The conduction behaviors, with respect to compacting pressure as well as total current density, were explained by differences in resistance of conduction pathways. Large observed differences between the materials were discussed in terms of the ratio of through‐plane and in‐plane resistivities. Additionally, we compared several methods to emulate defect sites, in order to evaluate their effect using the novel measurement cell and showed the effect of their size on the current distribution. Finally, we discuss improvements on the measurement setup.

Technical evaluation of proton exchange membrane (PEM) fuel cell performance – A review of the effects of bipolar plates coating

This work critically reviews recent developments in material characteristics and selection for the coating of bare metals used in the manufacture of bipolar plates (BPs) for PEM fuel cells. Several material types are considered in this work to provide the widest coverage of both established and emerging techniques. This includes discussion of defects observed in the coated material that emerged after the use of appropriate techniques to examine the coated surface after treatment. The work also provides a survey of the advances in the techniques used to coat the bare metal BPs.The work also considers the relative costs of the competing material and the methods used to apply them to the surface.The work discusses the results of the potentiostatic tests carried out on both the bare metal plates and the coated plates and for most cases it is possible to show that coated plates performed better than plates made of bare metals. This was confirmed by values obtained for properties such as interfacial contact resistance (ICR), corrosion resistance, corrosion current density (Icorr), and mechanical strength of the coatings. Also accelerated longevity studies confirmed the superiority of coated BPs.The work analyses the techniques used for coating and discusses their efficacy and the inherent drawbacks associated with the methods.It can be concluded that coating helps retards corrosion and improves the longevity of the fuel cell that enhances its cost competitiveness with other energy generation methods.

Protective coatings on stainless steel bipolar plates for proton exchange membrane (PEM) electrolysers

Proton exchange membrane (PEM) electrolysis is a promising technology for large H2 production from surplus electricity from renewable sources. However, the electrolyser stack is costly due to the manufacture of bipolar plates (BPP). Stainless steel can be used as an alternative, but it must be coated. Herein, dense titanium coatings are produced on stainless steel substrates by vacuum plasma spraying (VPS). Further surface modification of the Ti coating with Pt (8 wt% Pt/Ti) deposited by physical vapour deposition (PVD) magnetron sputtering reduces the interfacial contact resistance (ICR). The Ti and Pt/Ti coatings are characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and X-ray photoelectron microscopy (XPS). Subsequently, the coatings are evaluated in simulated and real PEM electrolyser environments, and they managed to fully protect the stainless steel substrate. In contrast, the absence of the thermally sprayed Ti layer between Pt and stainless steel leads to pitting corrosion. The Pt/Ti coating is tested in a PEM electrolyser cell for almost 200 h, exhibiting an average degradation rate of 26.5 μV h−1. The results reported here demonstrate the possibility of using stainless steel as a base material for the stack of a PEM electrolyser.

Manufacturing and characterization of bipolar fuel cell plate with textile reinforced polymer composites

An enhanced Vacuum Assisted Resin Transfer Molding (VARTM) process was studied for the manufacturing and characterization of bipolar plate with textile reinforced polymer composites. Rapid qualitative evaluation and quantitative characterization were conducted respectively to achieve an optimal manufacturing process design. The influence of process variables including pre-compaction cycle, post-filling time, curing pressure, etc., on the geometrical and mechanical properties of the textile reinforced polymer composites were investigated. The empirical optimized process design was then adapted for manufacturing of bipolar plate. The electrical properties of the bipolar plate were characterized by measuring its bulk (in-plane) conductivity according to the conventional four probe method. The influence of process conditions, carbon fabric design and nanofillers on the electrical properties of the bipolar plate were considered. The results show that the bipolar plate has a flexural strength in the range of 166.6–188.3MPa, which is a great improvement in comparison with the one based on highly filled or cut fibres reinforced polymer composites. However, the maximum bulk conductivity achieved is limited at 5902Sm−1 in this study, suggesting that further development effort is required for bipolar plate manufactured by textile reinforced polymer composites.

Alloy Selection and Die Design for Stamped Proton Exchange Membrane Fuel Cell (PEMFC) Bipolar Plates

Proton exchange membrane fuel cells have benefits over heat engines and batteries as an energy system for transportation, stationary power, and portable electronics. Before fuel cells can replace current energy systems, their manufacturing cost to performance ratio must be improved. The bipolar plate is a fuel cell component that contributes significantly to fuel cell manufacturing costs and is a key driver of performance. Metallic bipolar plates, with characteristic flow dimensions below the standard 1 mm, were fabricated using direct machining. Hydrogen/air fuel cells constructed of these plates were tested to ensure performance gains, using interdigitated flow operation and automobile-representative channel lengths. Finite Element Modelling (FEM) was used to investigate the manufacture of bipolar plates using low cost sheet metal stamping. Multiple bipolar plate alloys were compared based on their stampability, and die design parameters needed to stamp submillimeter channels were determined. Springback analysis was performed, and the effect of springback on fuel cell stack stresses was investigated.

Numerical–experimental investigations on the manufacturing of an aluminium bipolar plate for proton exchange membrane fuel cells by warm hydroforming

This research study focuses on the manufacturing of a bipolar plate used in proton exchange membrane fuel cells. In particular, the authors investigate the manufacturing of the part by means of warm hydroforming, adopting an aluminium alloy (AA6061) as sheet material. Both the channel profile (the reagent channel width and the die upper radius), and the bipolar plate geometries (in terms of channel layouts) are investigated by means of finite element simulations. Preliminary experimental investigations were carried out in order to define both the mechanical (flow curves) and strain behaviours (forming limit curves) of the adopted aluminium alloy according to temperature and strain rate. Subsequent finite element investigations aimed to define the channel profile by means of 2D models: a statistical approach was used to evaluate the dimension of the reagent channel width, the die upper radius and the sheet thickness. Finally, proposed bipolar plate geometries were investigated by running 3D simulations at different working temperatures and oil pressures in order to evaluate: (1) the bipolar plate geometry able to avoid regions with critical thinning and (2) suitable parameters for the warm hydroforming process.

Fabrication process analysis and experimental verification for aluminum bipolar plates in fuel cells by vacuum die-casting

There are various methods for the fabrication of bipolar plates, but these are still limited to machining and stamping processes. High-pressure die casting (HPDC) is an ideal process for the manufacture of bipolar plates This study aims to investigate the formability of bipolar plates for polymer electrolyte membrane fuel cells (PEMFCs) fabricated by vacuum HPDC of an Al–Mg alloy (ALDC6). The cavity of the mold consisted of a thin-walled plate (200mm×200mm×0.8mm) with a layer of serpentine channel (50mm×50mm). The location and direction of the channel in the final mold design was determined by computational simulation (MAGMA soft). In addition, simulation results for different conditions of plunger stroke control were compared to those from actual die-casting experiments. Under a vacuum pressure of 35kPa and for injection speeds of 0.3 and 2.5ms−1 in the low and high speed regions, respectively, the samples had few casting defects. In addition, the hardness was higher and porosity in microstructure was less than those of the samples made under other injection speed conditions. In case of thin-walled plates, vacuum die casting is beneficial in terms of formability compared to conventional die casting.

Effects of Different Particles Sizes of Graphite on the Engineering Properties of Graphites/Polypropylene Composites on Injection Molding Aplication

The injection molding of polymer composite is one of the promising and practical methods in the manufacturing of bipolar plates in mass production. Graphite filler with higher loading concentration is mainly used for this purpose. The particle size and composition (wt. %) of graphite filler material influences on the mechanical properties and electrical conductivity of composite materials. The main challenge is the reduction of flow ability during injection of high load filler material. Flow ability of feedstock material is an important factor in the process of injection molding. This paper presents a development of the rheology approach on the effect of particle size in material flow ability occurs in the injection molding process. Polypropylene (PP) as polymer matrix and graphite as conductive filler mixed together with different size to form feedstock material. Graphite purchase from local Asbury Graphite Mills, Inc, grade 3243 with particle size in average after sieve of ≤40, ≤100, and ≤150 μm. Proportions of polymer matrix and graphite at (PP / G) 25 / 75 wt. %. Mixing of graphite in PP matrix is done using an internal mixer (Thermo Haake) at 50 rpm, temperature at 200 oC. Rheology behaviors of graphite composite were measured using a capillary rheometer type Shimadzu CFT-500D, with a diameter 1 mm and length 10 mm. The fracture surface morphology was examined using scanning electron microscopy (SEM). The electrical conductivity of composite materials was measured by the four point probe. The hardness property measurement of conductive material composite was performed using a Dynamic ultra micro hardness tester using a Vickers typed diamond indenter. The results indicate that the level of viscosity and shear rate on all eligible mixed particle size capable of injectable. The properties of composite materials is the highest in three mix particle size (40/100/150 μm) for the electrical conductivity of 9.13 S.cm-1 and hardness at 34.3 HV. Viscosity of 56 Pa.s at a temperature of 200 oC and shear rates generated in 3231 s-1. The highest electrical conductivity for a single particle size is 49.2 S.cm-1 at 150 μm and hardness of Vickers to 47.2 HV at 100 um. The highest electrical conductivity and hardness due to the packing density and reinforcement different particle size.

Through-Mask Electroetching for Fabrication of Metal Bipolar Plate Gas Flow Field Channels

Transition of PEM fuel cells to the commercial market requires low-cost components, materials and manufacturing processes. Considering that bipolar plate manufacturing currently contributes to a significant percentage of the total fuel cell manufacturing cost, an inexpensive bipolar plate manufacturing process must be realized for fuel cells to achieve prominence in the commercial energy sector. A through-mask electro-etching process for high volume manufacturing of stainless steel bipolar plate gas flow field channels is being developed using pulse and pulse reverse electric fields. It has been demonstrated that the process can achieve a uniform channel depth, exhibits good repeatability for multiple experiments performed under the same conditions and the undercut beneath the photoresist mask varies linearly with channel depth indicating that pattern design compensation prior to photoresist patterning of the substrate to achieve the dimensional accuracy of the gas flow field channels and ribs is possible.

Manufacturing of Bipolar Plates for Micro-fuel Cells

Manufacturing of Bipolar Plates for Micro-fuel Cells

PEMFC Metallic Bipolar Plates: Effect of Manufacturing Method on Corrosion Resistance

Estimated high production volumes of bipolar plate manufacturing, strict dimensional and surface quality requirements and nature of their designs with thousands of meters of micro-channels demand engineers and scientists from production, design, and fuel cell operations sides look into alternative manufacturing processes, and compare their outcomes in terms of certain metrics such as productivity (plate/second), dimensional tolerances (um/mm), surface quality (Ra),cost ($), corrosion and contact resistance, and durability. In this study, the effect of manufacturing processes, stamping and hydroforming, on the corrosion resistance of thin metallic plates was investigated. The effects of process speed (stamping speed, hydroforming pressure rate) were also considered in this study. The results showed that in general SS316L possesses better corrosion resistance than SS304, as expected and reported in many literatures. In addition, while the effect of manufacturing processes was expected to degrade the corrosion resistance of the formed plates when compared the a non-deformed plate, this hypothesis only held true in the case of stamping as the hydroformed plates revealed better corrosion resistance than a non-deformed plate.

Stainless Steel Bipolar Plates.-Commercial and Technical Feasibility Study for Mass Production in Mexico

Stainless steel Type 444 is an excellent material for use in the manufacture of bipolar plates. It is comparable to austenitic stainless steel Type 316 in its corrosion resistance but has the advantage of being half less expensive. The coatings that had the best performance were chromium carbide and gold. Corrosion resistance of ferritic stainless steels 439 and 441, with a Ni-Cr and NiCrAlY coatings, were evaluated under simulated cathodic PEMFC environment. The corrosion current density of the coatings is higher than the US Department of Energy target value and they are not a feasible option to be used in bipolar plates for fuel cell applications. A possible explanation of the inadequate corrosion resistance is the segregation of the elements. The XRD and SEM measurements indicate that the corrosion mechanisms are different for NiCr and NiCrAlY. We have concluded that it is technically possible to produce bipolar plates in Mexico.