Toshihiko Kanezaki

Characteristics of Fatigue Crack Growth and Stress Corrosion Cracking in Aggressive Environments of Aluminum Alloys for Hydrogen Gas Containers

Hydrogen gas container is one of the critical components for fuel cell electric vehicle (FCEV), which is expected for CO2-free personal transportation. In order to choose an appropriate material for its metal boss and liner, crack growth resistance should be evaluated for various aspects such as fatigue crack growth (FCG) and stress corrosion cracking (SCC) in salt water or humid air environments for the purpose of commercial vehicle use. In the present study, FCG tests were carried out for A6061 and A6066 alloys in laboratory air and in 3.5% NaCl solution for compact (CT) and single edge notched (SEN) specimens. Some SEN specimens were cut from machined hydrogen container made of A6066 at the neck and the shoulder locations. SCC tests were carried out for A6061, A6066 and A6351 (fine and coarse grains) alloys in 3.5% NaCl solution and in humid air for CT specimen.Copyright

Characteristics of Corrosion Fatigue Crack Growth in Salt Water of Aluminum Alloys for Hydrogen Gas Containers

A hydrogen gas container is one of the critical components for fuel cell vehicles (FCV), which is expected for CO2-free personal transportation. In the early stage of commercial FCV, the major container structure will be a compressed hydrogen gas cylinder, which consists of metal or plastic linear with metal boss and carbon fiber reinforced plastics (CFRP). In order to choose an appropriate material for the metal boss and metal liner, corrosion resistance should be evaluated for various aspects such as corrosion fatigue crack growth (CFCG) and stress corrosion cracking (SCC) in the high pressure hydrogen as well as in salt water environment for the purpose of vehicle use. In the present study, CFCG characteristics were evaluated for several aluminum alloys in air and in salt waters with various concentrations. The results showed that the crack growth rates were accelerated in salt water for all the materials and their environmental sensitivities were compared. The concentrations of the salt water exhibited minor effect on the fatigue crack growth rates. These CFCG characteristics were compared with the corrosion test results based on the ISO 7866 Annex A [1]. A basic idea was proposed for the evaluation of compressed hydrogen gas containers and the important material properties were suggested.Copyright