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Title: Formation of Protective Nitride Surfaces for PEM Fuel Cell Metallic Bipolar Plates

Abstract

Selective gas nitridation of model Ni-base alloys was used to form dense, electrically-conductive and corrosion-resistant nitride surface layers, including TiN, VN, CrN, Cr2N, as well as a complex NiNbVN phase. Evaluation for use as a protective surface for metallic bipolar plates in proton exchange membrane fuel cells (PEMFC) indicated that CrN/Cr2N base surfaces hold promise to meet Department of Energy (DOE) performance goals for automotive applications. The thermally grown CrN/Cr2N surface formed on model Ni-Cr base alloys exhibited good stability and low electrical resistance in single-cell fuel cell testing under simulated drive-cycle conditions. Recent results indicate that similar protective Cr-nitride surfaces can be formed on less expensive Fe-Cr base alloys potentially capable of meeting DOE cost goals.

Authors:
 [1];  [1];  [2];  [2];  [1];  [3];  [3]
  1. ORNL
  2. National Renewable Energy Laboratory (NREL)
  3. Los Alamos National Laboratory (LANL)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); High Temperature Materials Laboratory; Shared Research Equipment Collaborative Research Center
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
OSTI Identifier:
1003560
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the Minerals Metals & Materials Society (JOM); Journal Volume: 58; Journal Issue: 8
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; ALLOYS; ELECTRIC CONDUCTIVITY; EVALUATION; FUEL CELLS; NITRIDATION; NITRIDES; PERFORMANCE; PLATES; PROTON EXCHANGE MEMBRANE FUEL CELLS; STABILITY; TESTING; fuel cell; coating; bipolar plate; nitride; corrosion

Citation Formats

Brady, Michael P, Yang, Bing, Wang, Heli, Turner, John, More, Karren Leslie, Wilson, Mahlon, and Garzon, Fernando. Formation of Protective Nitride Surfaces for PEM Fuel Cell Metallic Bipolar Plates. United States: N. p., 2006. Web. doi:10.1007/s11837-006-0054-4.
Brady, Michael P, Yang, Bing, Wang, Heli, Turner, John, More, Karren Leslie, Wilson, Mahlon, & Garzon, Fernando. Formation of Protective Nitride Surfaces for PEM Fuel Cell Metallic Bipolar Plates. United States. doi:10.1007/s11837-006-0054-4.
Brady, Michael P, Yang, Bing, Wang, Heli, Turner, John, More, Karren Leslie, Wilson, Mahlon, and Garzon, Fernando. Sun . "Formation of Protective Nitride Surfaces for PEM Fuel Cell Metallic Bipolar Plates". United States. doi:10.1007/s11837-006-0054-4.
@article{osti_1003560,
title = {Formation of Protective Nitride Surfaces for PEM Fuel Cell Metallic Bipolar Plates},
author = {Brady, Michael P and Yang, Bing and Wang, Heli and Turner, John and More, Karren Leslie and Wilson, Mahlon and Garzon, Fernando},
abstractNote = {Selective gas nitridation of model Ni-base alloys was used to form dense, electrically-conductive and corrosion-resistant nitride surface layers, including TiN, VN, CrN, Cr2N, as well as a complex NiNbVN phase. Evaluation for use as a protective surface for metallic bipolar plates in proton exchange membrane fuel cells (PEMFC) indicated that CrN/Cr2N base surfaces hold promise to meet Department of Energy (DOE) performance goals for automotive applications. The thermally grown CrN/Cr2N surface formed on model Ni-Cr base alloys exhibited good stability and low electrical resistance in single-cell fuel cell testing under simulated drive-cycle conditions. Recent results indicate that similar protective Cr-nitride surfaces can be formed on less expensive Fe-Cr base alloys potentially capable of meeting DOE cost goals.},
doi = {10.1007/s11837-006-0054-4},
journal = {Journal of the Minerals Metals & Materials Society (JOM)},
number = 8,
volume = 58,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni-Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitridemore » (CrN and Cr{sub 2}N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V{sub 2}O{sub 3}-Cr{sub 2}O{sub 3}, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe-27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.« less
  • Gas nitridation has shown excellent promise to form dense, electrically conductive and corrosion-resistant Cr-nitride surface layers on Ni–Cr base alloys for use as proton exchange membrane fuel cell (PEMFC) bipolar plates. Due to the high cost of nickel, Fe-base bipolar plate alloys are needed to meet the cost targets for many PEMFC applications. Unfortunately, nitridation of Fe-base stainless steel alloys typically leads to internal Cr-nitride precipitation rather than the desired protective surface nitride layer formation, due to the high permeability of nitrogen in these alloys. This paper reports the finding that it is possible to form a continuous, protective Cr-nitridemore » (CrN and Cr2N) surface layer through nitridation of Fe-base stainless steel alloys. The key to form a protective Cr-nitride surface layer was found to be the initial formation of oxide during nitridation, which prevented the internal nitridation typically observed for these alloys, and resulted in external Cr-nitride layer formation. The addition of V to the alloy, which resulted in the initial formation of V2O3–Cr2O3, was found to enhance this effect, by making the initially formed oxide more amenable to subsequent nitridation. The Cr-nitride surface layer formed on model V-modified Fe–27Cr alloys exhibited excellent corrosion resistance and low interfacial contact resistance under simulated PEMFC bipolar plate conditions.« less
  • Ferrite stainless steels (AISI441, AISI444, and AISI446) were successfully coated with 0.6 {micro}m thick SnO{sub 2}:F by low-pressure chemical vapor deposition and investigated in simulated PEMFC environments. The results showed that a SnO{sub 2}:F coating enhanced the corrosion resistance of the alloys in PEMFC environments, though the substrate steel has a significant influence on the behavior of the coating. ICP results from the testing solutions indicated that fresh AISI441 had the highest dissolution rates in both environments, and coating with SnO2:F significantly reduced the dissolution. Coating AISI444 also improved the corrosion resistance. Coating AISI446 steel further improved the already excellentmore » corrosion resistance of this alloy. For coated steels, both potentiostatic polarizations and ICP results showed that the PEMFC cathode environment is much more corrosive than the anode one. More dissolved metallic ions were detected in solutions for PEMFC cathode environment than those in PEMFC anode environment. Sn{sup 2+} was detected for the coated AISI441 and AISI444 steels but not for coated AISI446, indicating that the corrosion resistance of the substrate has a significant influence on the dissolution of the coating. After coating, the ICR values of the coated steels increased compared to those of the fresh steels. The SnO{sub 2}:F coating seems add an additional resistance to the native air-formed film on these stainless steels.« less
  • No abstract prepared.
  • Duplex 2205 stainless steel was deposited with 0.6 {micro}m thick SnO2:F coating; coated steel was characterized for PEMFC bipolar plate application. Compared with bare alloy, interfacial contact resistance (ICR) values of the coated 2205 steel are higher. SnO2:F coating adds its own resistance to the air-formed film on the steel. In a PEMFC anode environment, a current peak of ca. 25 {micro}A/cm2 registered at ca. 30 min for coated 2205 steel. It stabilized at ca. 2.0 {approx} -1.0 {micro}A/cm2. This peak is related to the complicated process of coating dissolution and oxide-layer formation. Anodic-cathodic current transfer occurred at ca. 200more » min polarization. In a PEMFC cathode environment, current was stable immediately after polarization. The stable current was ca. 0.5 {approx} 2.0 {micro}A/cm2 during the entire polarization period. AES depth profiles with tested samples and ICP analysis with the tested solutions confirmed the excellent corrosion resistance of the SnO2:F coated 2205 alloy in simulated PEMFC environments.« less