Addressing Hydrogen Embrittlement in the SAE J2579 Fuel Cell Vehicle Tank Standard Brian Somerday Sandia National Laboratories Livermore, CA, USA Christine Sloane SloaneSolutions, LLC Kewadin, MI, USA International Conference on Hydrogen Safety ICHS 2011 San Francisco, CA, USA September 14, 2011 Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under contract DE-AC04-94AL85000

SAE J2579 focuses on safety qualification of vessel in Compressed Hydrogen Storage System of FCVs Compressed Hydrogen Storage System (CHSS) boundary defined by interfaces that isolate stored high pressure H2 All containment vessel designs include metal components (e.g., composite vessels have boss and liner)

Hydrogen embrittlement accelerates fatigue cracking Safety qualification of vessel must consider hydrogen embrittlement of metal components Hydrogen embrittlement accelerates fatigue cracking a crack in H2 crack in N2 Nf = Ninitiation + Ngrowth Number of pressure cycles, N H2 Dp a Barthélémy, 1st ESSHS, 2006

Vessel safety qualification typically conducted by either engineering analysis or performance testing stress analysis: DK = Dp[f(a, t ,Ro, Ri)] Dp Ri Ro a t crack growth law: da/dN = C(DK)m engineering analysis performance testing pressure Design qualification in SAE standards based on performance testing Dp Nf Number of pressure cycles, N

Vessel safety qualification in SAE J2579 is based on performance testing Pneumatic test (H2) Hydraulic test Durability Performance Verification Test These performance tests do not evaluate “durability” under H2 gas pressure cycling, i.e., hydrogen embrittlement

Logic flow for addressing hydrogen embrittlement through performance testing in SAE J2579 Metals in vessel are 6061 Al or high-nickel 316 stainless steel? (SAE J2579 Appendix B.2.3) NO Metals in vessel meet acceptance criteria from materials testing in H2? (SAE J2579 Appendix C.15) YES YES NO Vessel qualified using existing expected-service (pneumatic) and durability (hydraulic) performance tests (SAE J2579 Section 5.2.2) Vessel qualified using existing performance tests (SAE J2579 Section 5.2.2) AND new (more extreme) H2 gas cycling test (SAE J2579 Appendix C.14) Recent activity focused on Appendix C.14 and Appendix C.15

Logic flow for addressing hydrogen embrittlement through performance testing in SAE J2579 Metals in vessel are 6061 Al or high-nickel 316 stainless steel? (SAE J2579 Appendix B.2.3) NO Metals in vessel meet acceptance criteria from materials testing in H2? (SAE J2579 Appendix C.15) YES YES NO Vessel qualified using existing expected-service (pneumatic) and durability (hydraulic) performance tests (SAE J2579 Section 5.2.2) Vessel qualified using existing performance tests (SAE J2579 Section 5.2.2) AND new (more extreme) H2 gas cycling test (SAE J2579 Appendix C.14) Tests in Appendix C.15 determine whether material has unrestricted (i.e., not design specific) hydrogen compatibility

Appendix C.15 materials test: slow strain rate tensile test Issues addressed: Acceptance criterion established as RAH2/RAair > 0.7 Test conducted in H2 gas or with “precharged” H Test temperature(s) H2 H2 H H H2 OR H H2 H H H2 H2 H RA

Appendix C.15 materials test: fatigue crack initiation test Issues addressed: R ratio, i.e., ratio of Smin to Smax Stress-cycle frequency (f) Test temperature(s) Acceptance criterion, e.g., Nf(H2)/Nf(air) ~ 1 The locus of stress vs. number of cycles to failure points can shift depending on the environmental exposure. stress (S) H2 air cycles to failure (Nf ~ Ninitiation)

Appendix C.15 materials test: “long crack” growth test Issues addressed: Load-cycle frequency Test temperature(s) Acceptance criterion? da/dN H2 air DK

Load-cycle frequency must be specified for fatigue tests conducted in H2 gas A.H. Priest, British Steel, 1983 Magnitude of accelerated fatigue cracking in H2 gas depends on load-cycle frequency

Logic flow for addressing hydrogen embrittlement through performance testing in SAE J2579 Metals in vessel are 6061 Al or high-nickel 316 stainless steel? (SAE J2579 Appendix B.2.3) NO Metals in vessel meet acceptance criteria from materials testing in H2? (SAE J2579 Appendix C.15) YES YES NO Vessel qualified using existing expected-service (pneumatic) and durability (hydraulic) performance tests (SAE J2579 Section 5.2.2) Vessel qualified using existing performance tests (SAE J2579 Section 5.2.2) AND new (more extreme) H2 gas cycling test (SAE J2579 Appendix C.14) Performance test in Appendix C.14 evaluates design-specific hydrogen compatibility

Performance test in Appendix C Performance test in Appendix C.14 intended to account for H2-accelerated fatigue cracking Dp H2 filler material Issues addressed: Pressure-cycle profile Test temperature Number of cycles a H2 pressure rise time > 5 min hold time > 2 min 125% NWP 2 MPa Number of pressure cycles, N

SAE working group on hydrogen embrittlement represents international effort Europe Adam Opel BMW Robert Bosch Linde Japan JARI AIST/HYDROGENIUS SAE J2579 Appendix B.2.3 SAE J2579 Appendix C.15 SAE J2579 Appendix C.14 USA GM Sandia National Laboratories

Summary Vehicle tank standard SAE J2579 describes safety qualification for Compressed Hydrogen Storage System Safety qualification based on performance testing Hydraulic long-term durability test does not account for hydrogen embrittlement New tests developed for SAE J2579 to evaluate hydrogen compatibility of vessel designs Material-level testing determines whether material has unrestricted (i.e., not design specific) hydrogen compatibility Component-level testing evaluates design-specific hydrogen compatibility