Biomimetic flow fields for proton exchange membrane fuel cells: A review of design trends

Bipolar Plate design is one of the most active research fields in Polymer Electrolyte Membrane Fuel Cells (PEMFCs) development. Bipolar Plates are key components for ensuring an appropriate water management within the cell, preventing flooding and enhancing the cell operation at high current densities. This work presents a literature review covering bipolar plate designs based on nature or biological structures such as fractals, leaves or lungs. Biological inspiration comes from the fact that fluid distribution systems found in plants and animals such as leaves, blood vessels, or lungs perform their functions (mostly the same functions that are required for bipolar plates) with a remarkable efficiency, after millions of years of natural evolution. Such biomimetic designs have been explored to date with success, but it is generally acknowledged that biomimetic designs have not yet achieved their full potential. Many biomimetic designs have been derived using computer simulation tools, in particular Computational Fluid Dynamics (CFD) so that the use of CFD is included in the review. A detailed review including performance benchmarking, time line evolution, challenges and proposals, as well as manufacturing issues is discussed.Ministerio de Ciencia, Innovación y Universidades ENE2017-91159-EXPMinisterio de Economía y Competitividad UNSE15-CE296

Numerical study on the formability of metallic bipolar plates for Proton Exchange Membrane (PEM) fuel cells

Thin stamped bipolar plates (BPPs) are viewed as promising alternatives to traditional graphite BPPs in proton exchange membrane fuel cells. Metallic BPPs provide good thermal/electrical conductivity and exhibit high mechanical strength, to support the loads within the stack. However, BPPs manufactured by stamping processes are prone to defects. In this study, the effect of the tool’s geometry on the thin sheet formability is investigated through finite element simulation. Despite the broad variety of flow field designs, most of BPPs comprise two representative zones. Hence, in order to reduce the computational cost, the finite element analysis is restricted to these two zones, where the deformation induced by the stamping tools is investigated. The channel/rib width, the punch/die fillet radii, and the channel depth are the parameters studied. The analysis is conducted for a stainless steel SS304 with a thickness of 0.15 mm. The results show that the maximum value of thinning occurs always in the U-bend channel section, specifically in the fillet radius of the die closest to the axis of revolution.This research was funded by the Portuguese Foundation for Science and Technology (FCT) under projects PTDC/EMS-TEC/0702/2014 (POCI-01-0145-FEDER-016779) and PTDC/EMS-TEC/6400/2014 (POCI-01-0145-FEDER-016876) by UE/FEDER through the program COMPETE 2020. The support under the project MATIS (CENTRO-01-0145-FEDER-000014) is also acknowledged

INVESTIGATIONS ON THE MICRO-SCALE SURFACE INTERACTIONS AT THE TOOL AND WORKPIECE INTERFACE IN MICRO-MANUFACTURING OF BIPOLAR PLATES FOR PROTON EXCHANGE MEMBRANE FUEL CELLS

Micro-forming studies have been more attractive in recent years because of miniaturization trend. One of the promising metal forming processes, micro-stamping, provides durability, strength, surface finish, and low cost for metal products. Hence, it is considered a prominent method for fabricating bipolar plates (BPP) with micro-channel arrays on large metallic surfaces to be used in Proton Exchange Membrane Fuel Cells (PEMFC). Major concerns in micro-stamping of high volume BPPs are surface interactions between micro-stamping dies and blank metal plates, and tribological changes. These concerns play a critical role in determining the surface quality, channel formation, and dimensional precision of bipolar plates. The surface quality of BPP is highly dependent on the micro-stamping die surface, and process conditions due to large ratios of surface area to volume (size effect) that cause an increased level of friction and wear issues at the contact interface. Due to the high volume and fast production rates, BPP surface characteristics such as surface roughness, hardness, and stiffness may change because of repeated interactions between tool (micro-forming die) and workpiece (sheet blank of interest). Since the surface characteristics of BPPs have a strong effect on corrosion and contact resistance of bipolar plates, and consequently overall fuel cell performance, evolution of surface characteristics at the tool and workpiece should be monitored, controlled, and kept in acceptable ranges throughout the long production cycles to maintain the surface quality. Compared to macro-forming operations, tribological changes in micro-forming process are bigger challenges due to their dominance and criticality. Therefore, tribological size effect should be considered for better understanding of tribological changes in micro-scale. The integrity of process simulation to the experiments, on the other hand, is essential. This study describes an approach that aims to investigate the surface topography changes during long-run micro-stamping of BPPs, and establish relationships between surface roughness–corrosion resistance and surface roughness–contact resistance characteristics of BPPs. Formability levels of formed BPPs and repeatability characteristics of the process were investigated. In addition, blank thickness changes, von-Mises stress, plastic strain levels and distributions of micro-stamping process were determined via finite element analysis (FEA). Test results revealed that the surface roughness change for the stamping dies and BPPs was unsteady (no trend) due to the continuous change of surface topography (i.e. asperity deformation). Sub-micron range local plastic deformations on stamping dies led to surface topography changes on BPP in long-run manufacturing case. As surface defects trigger corrosion, the correlation between surface roughness and corrosion resistance of BPPs was found to be direct. Increasing number of surface irregularities (asperities) lowered contact surface area that resulted in increased contact resistance. ZrN coated BPPs, on the other hand, did not change surface roughness, however; it improved the protection of BPPs against corrosion significantly. In addition, ZrN coating increased the conductivity of BPPs and reduced the contact resistance between BPP and gas diffusion layer (GDL), at certain extent. As dimensional stability and repeatability was confirmed in forming of both uncoated and coated BPPs during the long run manufacturing, different formability levels were achieved for coated and uncoated samples. Lower channel height values were obtained for coated plates because of the different surface hardness of uncoated and coated plates. In tribological size effect part of study, micro stamping experiments using three different dies with distinct channel height values at different stamping force levels were performed. It was concluded that decrease in forming die dimensions led to increase in coefficient of friction as previously reported by other researchers as one of the consequences of tribological size effect. On the other hand, coefficient of friction values were not affected by the force levels used in the experiments and simulations, whereas plastic strain, equivalent stress, and formability levels were increased with increasing stamping force, as expected. In essence, this study proposed a methodology to investigate the long-run manufacturing effects on dimensional stability and surface characteristics of micro-stamped sheets. It also correlates these parameters to fuel cell performance measures such as interfacial contact and corrosion resistance

Evaluating the Effect of Metal Bipolar Plate Coating on the Performance of Proton Exchange Membrane Fuel Cells

Environmental concerns of greenhouse gases (GHG) effect from fossil commodities and the fast increase in global energy demand have created awareness on the need to replace fossil fuels with other sources of clean energy. PEM fuel cell (PEMFC) is a promising source of energy to replace fossil fuels. The commercialization of the cell depends on its price, weight and mechanical strength. Bipolar plates are among the main components of PEMFC which perform some significant functions in the fuel cell stack. Metal bipolar plate is considered by the research community as the future material for fuel cells. However, surface coating is required for metals to enhance its corrosion resistance, hydrophilicity and interfacial contact resistance (ICR) in PEM fuel cells. Open pore cellular metal foam (OPCMF) materials have been used to replace the conventional flow field channel in recent times due to its low electrical resistance, high specific area and high porosity; however, it endures the same corrosion problem as the metallic bipolar plate. This investigation offers an overview on different types of bipolar plates and techniques in coating metallic bipolar platse and open pore metal foam as flow field channel materials to improve the corrosion resistance which will eventually increase the efficiency of the fuel cell appreciably

Degradation aspects of water formation and transport in Proton Exchange Membrane Fuel Cell: A review

This review paper summarises the key aspects of Proton Exchange Membrane Fuel Cell (PEMFC) degradation that are associated with water formation, retention, accumulation, and transport mechanisms within the cell. Issues related to loss of active surface area of the catalyst, ionomer dissolution, membrane swelling, ice formation, corrosion, and contamination are also addressed and discussed. The impact of each of these water mechanisms on cell performance and durability was found to be different and to vary according to the design of the cell and its operating conditions. For example, the presence of liquid water within Membrane Electrode Assembly (MEA), as a result of water accumulation, can be detrimental if the operating temperature of the cell drops to sub-freezing. The volume expansion of liquid water due to ice formation can damage the morphology of different parts of the cell and may shorten its life-time. This can be more serious, for example, during the water transport mechanism where migration of Pt particles from the catalyst may take place after detachment from the carbon support. Furthermore, the effect of transport mechanism could be augmented if humid reactant gases containing impurities poison the membrane, leading to the same outcome as water retention or accumulation. Overall, the impact of water mechanisms can be classified as aging or catastrophic. Aging has a long-term impact over the duration of the PEMFC life-time whereas in the catastrophic mechanism the impact is immediate. The conversion of cell residual water into ice at sub-freezing temperatures by the water retention/ accumulation mechanism and the access of poisoning contaminants through the water transport mechanism are considered to fall into the catastrophic category. The effect of water mechanisms on PEMFC degradation can be reduced or even eliminated by (a) using advanced materials for improving the electrical, chemical and mechanical stability of the cell components against deterioration, and (b) implementing effective strategies for water management in the cell

고분자 전해질막 연료전지의 3차원 양극 유로 설계에 따른 성능 변화 연구

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부(멀티스케일 기계설계전공), 2022. 8. 김민수.고분자 전해질막 연료전지의 핵심 부품 중 하나인 양극 분리판은 그 설계에 따라 연료전지의 성능, 연료 효율, 내구성 그리고 운영 및 제조 비용을 변화시킨다. 연료전지 내부 화학반응의 고유한 특성에 따라 유로의 기하학적 특성이 개별적으로 연구되어야 고효율 및 높은 내구성을 가지는 연료전지 시스템을 개발할 수 있다. 반응물의 고갈과 물 배출 저하는 연료전지 성능 저하에 직접적인 영향을 미친다. 따라서 적정 수준의 압력 강하로 효율적인 물질전달을 이룰 수 있는 분리판 개발이 필수적이다. 일반적으로 양극 유로를 따라 물 축적이 심화되고 이로 인해 반응물이 제대로 전달되지 않는 영역이 발생하므로 본 연구에서는 양극 유로의 설계에 대하여 실험적, 해석적 연구를 진행하였다. 본 연구에서는 3D 프린팅 기술을 활용하여 양극 유로로써 사용될 수 있는 3D 구조체를 제작하고 이를 개선할 수 있는 방안을 도출하고자 하였다. 구조체의 기하학적 형상을 연료전지 성능에 친화적으로 변화시키기 위하여 유로 단위 폭과 경사도를 변화시킬 수 있는 형상 수치를 선정하고 3D 프린터로 제작될 수 있도록 그 구조를 단순화 시켰다. 유로의 단위 폭과 경사도를 유동 진행 방향에 따라 다르게 변화시켜 성능을 측정하였고 결과에 따라 각 형상 변수의 최적 배치를 찾았다. 이후 두 최적 배치를 하나로 결합한 경우 균일하게 배치된 대조 실험군과 비교하여 13.0%의 최대 출력 증가를 얻었다. 전기화학임피던스분광법을 활용하여 해당 배치가 대조군과 비교하여 더 낮은 농도 손실을 가짐을 보였다. 성능 향상의 세부적인 원인을 밝히기 위하여 유동 해석 프로그램 중 하나인 ANSYS FLUENT를 활용하였다. 3차원 유동 해석의 시간을 줄이고, 단일 유닛 내의 유동 특성 변화를 독립적으로 분석하기 위하여 1열의 단일 유닛 배치를 기준으로 해석을 진행하였다. 출구부의 단일 유닛들을 실험으로 검증했던 배치들과 같은 경향을 가지도록 배열하고 해당 변화들이 연료전지 성능에 영향을 줄 수 있는 유동 특성에 어떠한 변화를 가져오는지 분석하였다. 두꺼운 벽 두께와 좁은 채널 폭은 낮은 접촉 저항과 향상된 유동 속도로 인해, 유로 내의 물 축적이 반영되는 실제 상황에서 성능 변화를 기대해볼 수 있었지만, 유동이 기체확산층과 닿는 면적을 줄임으로써 다공성의 기체확산층을 통과하는 반응물의 물질 전달을 방해하는 것이 드러났다. 경사 구조는 특히 기체확산층과 수직 방향의 유속을 증가시키는 것으로 나타났으며 가장 효율적인 유로 내 물질 전달 능력 향상에 기여하였다. 전반적인 유속의 증가는 실제 실험 시 축적된 액적의 제거에 긍정적일 것으로 기대되었다. 더 나아가 실험에서 측정할 수 없었던 유동 영역 내의 성능 분포에 대한 결과도 얻을 수 있었는데, 비슷한 전류 밀도를 얻을 수 있더라도 배치의 방향에 따라 연료전지 입구와 출구 사이의 성능 편차가 변화하였다. 더욱 발전된 양극 유로 배치 전략에 대해 제시하기 위하여 더 큰 유동 영역에서 해석을 진행하였다. 잠재적으로 물 축적과 물질 전달 저해가 우려되는 영역이 유로의 주된 진행 방향과 수직한, 즉 유로의 폭 방향으로 형성되는 것이 예상되어, 유로 폭 방향으로도 불균일한 유로의 형상 변화를 꾀할 수 있음을 시사했다. 구조의 벽 두께를 유로 폭 방향에 따라 변화를 줌으로써 중앙부의 유동 저항을 늘리고 주변부의 유동 저항을 감소시켜 성능 저하가 우려되는 영역에서 물질 전달을 강화시킬 수 있었다. 유동 해석을 통하여 전류밀도의 불균일함이 일정부분 해소됨을 보였으며 이를 실험적으로 추가 검증하기 위하여 내구성 실험이 진행되었다. 그 결과 폭과 길이 방향으로 모두 유로 형상이 불균일하게 변하는 설계 전략으로 유동 불균일로 인한 내구성 감소를 완화시킬 수 있음을 보였다.Bipolar plate design in PEMFC can change performance, fuel efficiency, cell and stack duration and manufacturing costs. According to unique characteristics of chemical reaction along the fuel cell, geometric characteristics of flow channel have to be separately studied to develop highly efficient and durable fuel cell system. Starvation of reactants and severe water accumulation can be major causes operating failure and performance degradation. Therefore efforts for enhancing mass transfer capability with moderate pressure drop are necessary. Since water accumulation and dead-zone formation are normally severe along the cathode flow channel, design of cathode flow channel was examined through experimental and numerical methods. In this study, modification in flow channel design was investigated utilizing 3D printed structure as flow channel in unit fuel cell. Selecting two effective geometric parameters, channel width and bottom-rear channel depth, and simplifying curvature of complex design, various types of 3D structure were manufactured. To observe effect of modification separately, width varied and slope varied arrangements were tested individually, finding the best arrangement of each strategy. Combining two strategy into one arrangement, the best arrangement showed 13.0% higher maximum power density compared with uniform arrangement. Compared with 3D printed parallel flow channel which had the same structure-gas diffusion contact area, the best arrangement showed 39.4% higher maximum power density. Moreover, even if uniform arrangement of 3D structure showed 10.4% higher performance in unit cell. EIS data also showed that non-uniform arrangement had lower concentration loss. To expose detail causes of performance enhancement, CFD analysis using ANSYS FLUENT was conducted along a single row of 3D structure. Replacing 3D structure near outlet to differently designed structure, various patterns tested in experimental study were analyzed through CFD. Narrow channel width with thicker wall thickness showed lower contact resistance and enhanced overall velocity, however, narrowed interface between GDL and reactants flow lowered mass transfer though porous structure of GDL. Sloped structure separately enhanced velocity, especially perpendicular with GDL surface, efficiently enhancing mass transfer capability. Analysis with porous structure implied that velocity fluctuation along the channel and on surface of gas diffusion layer could enhance mass transfer. Comparing with experimental results, overall velocity could be positive with water removal and although current density distribution was not be measured in experiment, performance uniformity could be measured through CFD analysis and direction of arrangement was revealed to have significant effect to performance uniformity. To suggest advanced non-uniform arrangement, CFD analysis for larger domain was performed. Geometry modification along the width direction targeting potential dead-zone formation was applied, reducing flow resistance at side of the active area by making difference in wall thickness. Firstly, through CFD analysis, uniformity enhancement through width direction varied non-uniform arrangement was confirmed. Finally, durability test with performance measurement was conducted. The results showed that arrangement with width and length direction non-uniformity showed the highest durability compared with the other. Maximum power density decrease ratio was reduced from 12.4% to 8.6% and high frequency resistance increase ratio was reduced from 18.0% to 12.9% after 60000 cycles of accelerated stress test.Abstract i Contents v List of Figure viii List of Tables xiv Nomenclature xv Chapter 1. Introduction 1 1.1. Background of the study 1 1.2. Literature survey 7 1.2.1. Conventional flow channel design 7 1.2.2. Advanced flow channel design 16 1.2.3. Non-uniform design along active area 25 1.3. Objectives and scopes 34 Chapter 2. Experimental study on PEMFC with non-uniformly arranged 3D structures 36 2.1. Introduction 36 2.2. Preparation for experiment 38 2.2.1. Designing and manufacturing 3D structures 38 2.2.2. Arrangement of 3D printed single structures 48 2.2.3. Experiments on single cell 53 2.3. Results and discussion 57 2.3.1. Effect of width non-uniformity on the single cell performance 57 2.3.2. Effect of slope non-uniformity on the single cell performance 66 2.3.3. Mixed non-uniform arrangements 70 2.4. Summary 76 Chapter 3. Computational fluid dynamics analysis on 3D structures at various scales 78 3.1. Introduction 78 3.2. Preparation for CFD analysis 80 3.2.1. Numerical models 80 3.2.2. Model validation 89 3.3. Results and discussion 112 3.3.1. General characteristics of 3D structure as flow channel 112 3.3.2. Local characteristics in different geometrical parameters 134 3.3.3. Arrangement direction effects on fuel cell performance 148 3.4. Summary 157 Chapter 4. 3D structure arrangements for large active area 159 4.1. Introduction 159 4.2. Design strategies for fuel cell scaling up 168 4.2.1. Width varied non-uniform pattern along width direction 168 4.2.2. Slope varied non-uniform pattern along width direction 181 4.3. Durability test for fuel cell with large active area 194 4.4. Summary 202 Chapter 5. Concluding remarks 204 Reference 210박

Bio-inspired design, fabrication and testing of bipolar plates for PEM fuel cells

The flow field of a bipolar plate distributes reactants for polymer electrolyte membrane (PEM) fuel cells and removes the produced water from the fuel cells. It greatly influences the performance of fuel cells, especially the concentration losses. Two approaches were developed to improve flow field designs in this dissertation. One is inspired by the biological circulatory structures and called bio-inspired designs, which have great potential to transport reactant efficiently and hence improve fuel cell performance. Another way is using a network-based optimization model to optimize the conventional flow field configurations, i.e., pin-type, parallel and serpentine designs, to improve flow distributions within the channels. A three-dimensional, two-phase numerical model was developed to investigate the mass, velocity and pressure distributions within the different flow fields and also the final fuel cell performance. Selective Laser Sintering, which provides a cost- and time-efficient way to build parts with complicated geometries, was used to fabricate graphite composite bipolar plates with these developed designs. Different graphite materials, including natural graphite, synthetic graphite, carbon black, and carbon fiber, were investigated in order to achieve higher electrical conductivity and flexural strength of the fabricated bipolar plates. Experimental testing of the PEM fuel cells with these fabricated bipolar plates was carried out to verify the numerical model and compare the performance for different flow field designs. Both the numerical and experimental results demonstrated that the bio-inspired designs and the optimized designs could substantially improve the fuel cell performance compared to the traditional designs --Abstract, page iv

Experimental and numerical analysis of fuel cells

Fuel Cells are attractive power source for use in electronic applications. Physical phenomena (water generation, saturation effect in fuel cell, poisoning, and thermal stress) are studied that governs the operation of a Proton Exchange Membrane Fuel Cell (PEMFC) and Solid Oxide Fuel cell (SOFC). Additionally, experimental studies and numerical simulations on PEMFC gas flow channel, the determination of the impact of the single channel fuel cell are presented. Furthermore, preliminary study is done for the application of APS (Air Plasma Spray) to SOFC and adhesion of anode and cathode with electrolytes for the determination of parameters involved in manufacturing the components of fuel cell. The new aspects on physical phenomena are significantly different from the currently popular relationships used in fuel cells as they are simplified from simulation and experimental results. In prior work, the physical phenomena such as water generation, saturation effect in fuel cell, poisoning, and thermal stress etc. are either assumed or used as adjustment parameters to simplify them or to achieve best fits with polarization data. In this work, physical phenomena are not assumed but determined via newly developed experimental and numerical techniques. The experimental fixtures and procedures were used to find better ways to control parameters of gas flow channel configurations for optimizing gas flow rates and performance, and gas flow channel pressure swing for CO poisoning recovery. The experimental results reveal controlling parameters for the mentioned cases and innovative design for Fuel cells. Numerical modeling were used to 2D and later 3D for simplification of single channel fuel cell model, transient localized heating to the catalyst layer for CO recovery, thermal stress that developed during SOFC fabrication by High Temperature vacuum Tube Furnace (HTVTF), and Gas Diffusion Layer and Gas Flow Channel (GDL-GFC) interfacial conditions with results based on commonly used relationships from the PEMFC literature. The modeling works reveal substantial impact on predicted GDL saturation, and consequently cause a significant impact on cell performance. Computational parametric relations and polarization curve results are compared to experimental polarization behavior which achieved a comparable relation

ANALISIS VARIASI CORNER RADIUS CETAKAN BIPOLAR PLATE SERPENTINE DAN BESAR TEKANAN PADA PROSES PEMBENTUKAN SUPERPLASTIS DENGAN METODE SIMULASI KOMPUTER

Permasalahan kelangkaan energi merupakan permasalahan bersama yang harus di cari solusinya. Banyak peneliti di dunia memfokuskan risetnya pada sumber energi terbarukan. Fuel cell adalah salah satu teknologi yang dapat digunakan untuk mendapatkan energi terbarukan dengan cara mengonversi hidrogen dan oksigen menjadi energi listrik. Bipolar plate adalah komponen penting dari fuel cell, dimana bipolar plate menyumbang sekitar 80 % dan 45 % dari berat dan biaya pembuatan fuel cell. Pada proses fabrikasi bipolar plate sering terjadi ke tidak sesuaian pada dimensi, baik ukuran kedalaman saluran maupun cacat pada area corner hasil fabrikasi. Penelitian ini bertujuan untuk mendapatkan desain cetakan bipolar plate serpentine dengan kedalaman saluran alir yang  tinggi, dengan menggunakan metode simulasi komputer. Pada penelitian ini proses pembentukan superplastis akan di simulasikan dengan memvariasikan corner radius cetakan (0; 0,3; 0,5 dan 0,7 mm) dan besar tekanan (0,75; 1; 1,25 dan 1,5 MPa). Hasil simulasi menunjukkan bahwa semakin besar tekanan dan corner radius pada cetakan bipolar plate serpentine, maka kedalaman saluran alir bipolar plate akan semakin besar. Kedalaman saluran alir maksimum diperoleh pada hasil simulasi dengan corner radius cetakan 0,7 mm dan  tekanan 1,5 MPa

Investigations on the Effect of Manufacturing on the Contact Resistance Behavior of Metallic Bipolar Plates for Polymer Electrolyte Membrane Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) have emerged as a strong and promising candidate to replace internal combustion engines (ICE) due their high efficiency, high power density and near-zero hazardous emissions. However, their commercialization waits for solutions to bring about significant cost-reductions and significant durability for given power densities. Bipolar plate (BPP) with its multi-faceted functions is one of the essential components of the PEMFC stacks. Stainless steel alloys are considered promising materials of choice for bipolar plate (BPP) applications in polymer electrolyte membrane fuel cells (PEMFC) due to their relatively low cost and commercial availability in thin sheets. Stainless steel materials build a protective passive metal oxide layer on their surface against corrosion attack. This passive layer does not demonstrate good electrical conductivity and increases interfacial electric contact resistance (ICR) between BPP and gas diffusion layer GDL in PEMFC. Lower ICR values are desired to reduce parasitic power losses and increase current density in order to improve efficiency and power density of PEMFC. This study aimed to bring about a broader understanding of manufacturing effects on the BPP contact resistance. In first stage, BPP samples manufactured with stamping and hydroforming under different process conditions were tested for their electrical contact resistance characteristics to reveal the effect of manufacturing type and conditions. As a general conclusion, stamped BPPs showed higher contact conductivity than the hydroformed BPPs. Moreover, pressure in hydroforming and geometry had significant effects on the contact resistance behavior of BPPs. Short term corrosion exposure was found to decrease the contact resistance of bipolar plates. Results also indicated that contact resistance values of uncoated stainless steel BPPs are significantly higher than the respective target set by U.S. Department of Energy. Proper coating or surface treatments were found to be necessary to satisfy the requirements. In the second stage, physical vapor deposition technique was used to coat bipolar plates with CrN, TiN and ZrN coatings at 0.1, 0.5 and 1 μm coating thicknesses. Effects of different coatings and coating thickness parameters were studied as manufactured BPPs. Interfacial contact resistance tests indicated that CrN coating increased the contact resistance of the samples. 1 µm TiN coated samples showed the best performance in terms of low ICR; however, ICR increased dramatically after short term exposure to corrosion under PEMFC working conditions. ZrN coating also improved conductivity of the SS316L BPP samples. It was found that the effect of coating material and coating thickness was significant whereas the manufacturing method and BPP channel size slightly affected the ICR of the metallic BPP samples. Finally, effect of process sequence on coated BPPs was investigated. In terms of ICR, BPP samples which were coated prior to forming exhibited similar or even better performance than coated after forming samples. Thus, continuous coating of unformed stripes, then, applying forming process seemed to be favorable and worth further investigation in the quest of making cost effective BPPs for mass production of PEMFC