Optimized Cr-nitride film on 316L stainless steel as proton exchange membrane fuel cell bipolar plate
Introduction
Bipolar plate is an important component of proton exchange membrane fuel cell (PEMFC), and it accounts for most of the total weight. The bipolar plate serves as the functions of distributing reactants uniformly over the active areas, removing heat from the active areas, collecting currents from cells, preventing leakage of reactants and coolant. An ideal bipolar plate material should have the characteristics as follows: (1) high corrosion resistance in PEMFC environment; (2) low interfacial contact resistance; (3) big contact angle with water; (4) lightweight; (5) high mechanical strength; and (6) cost-effective etc.
Forming a film with good corrosion resistance and high interfacial conductivity on stainless steel is one of the possible solutions. Metal nitrides are the promising surface modification materials for metal bipolar plate owing to their good corrosion resistance and high conductivity. Most of the researches have been focused on Cr-nitrides in recent years [1], [2], [3], [4], [5], [6], [7], [8], [9], [10]. In our previous work [11], Cr-nitride gradient films were coated on 316L stainless steel by pulsed bias arc ion plating (PBAIP) as bipolar plate for PEMFC. The composition of film varied with the flow rates of N2. Films obtained at N2 gas flow rates from 25 to 100 sccm exhibited high interfacial conductivity, good corrosion resistance and big contact angle, which showed great potential in the application of PEMFC.
The aim of the present work was to optimize the flow rate of N2 and obtain bipolar plate with better performance. Surface micrograph, film thickness, film composition, corrosion resistance, interfacial conductivity and contact angle with water of the bipolar plate sample prepared at the optimal flow rate of N2 were investigated.
Section snippets
Experimental
The 316L stainless steel (bright annealed) with the size of 100 × 100 × 0.1 mm3 was chosen as the base metal of bipolar plate. Details of forming the Cr-nitride films are described in our previous paper [10]. By changing the flow rate of N2, film with different composition could be obtained. However, the total pressure in the chamber, which is a sum of the N2 pressure and the Ar pressure, was kept constant at 5.0 × 10−3 Pa. The flow rates of N2 conducted in this study are listed in Table 1. In this
Optimization of the flow rate of N2
The corrosion resistance and interfacial conductivity are the two main properties of metal bipolar plate materials. The parameters of passive current density (the current density under passivation potential) and interfacial contact resistance were used to evaluate theses properties. All the bipolar plate samples were prepared at different flow rates of N2 by PBAIP. Passive current density in 0.5 M H2SO4 + 5 ppm F− solution at 25 °C and initial contact resistance with carbon paper under 1.2 MPa of all
Conclusions
Different compositions of Cr-nitride films could be obtained by changing the flow rate of N2 during PBAIP process. The bipolar plate sample produced at 20 sccm N2 exhibited the best corrosion resistance and the highest interfacial conductivity simultaneously.
In the film obtained at the optimal flow rate of N2, the atomic ratio of Cr to N was very close to 2:1 and CrN phase with crystal planes of (111), (200), (220) and (311) was found.
Potentiodynamic and potentiostatic tests performed at 70 °C
Acknowledgments
This work was financially supported by the National High Technology Research and Development Program of China (863 Program, No. 2007AA03Z221).
References (11)
- et al.
A study of the corrosion behaviour and protective quality of sputtered chromium nitride coatings
Surf Coat Technol
(2000) - et al.
Preferential thermal nitridation to form pin-hole free Cr-nitrides to protect proton exchange membrane fuel cell metallic bipolar plates
Scripta Mater
(2004) - et al.
Corrosion behavior of CrN, Cr2N and π phase surfaces on nitrided Ni-50Cr for proton exchange membrane fuel cell bipolar plates
Corros Sci
(2006) - et al.
Thermally nitrided stainless steels for polymer electrolyte membrane fuel cell bipolar plates: part 2. Beneficial modification of passive layer on AISI446
J Power Sources
(2004) - et al.
Thermally nitrided stainless steels for polymer electrolyte membrane fuel cell bipolar plates: part 1: model Ni-50Cr and austenitic 349™ alloys
J Power Sources
(2004)
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