Hydrogen Permeability and Delayed Failure of Polarized Martenstic Steels

Hydrogen permeability and delayed failure characteristics were directly correlated under cathodic and anodic polarization for 9-4-45 and 4340 high strength steels. At cathodic potentials they both exhibited the usual increased susceptibility to failure with increasing cathodic potential. With increasingly anodic applied potential, the 9-4-45 displayed decreased times to failure, increased hydrogen permeability and surface pitting. The time to failure in 4340 did not respond to anodic polarization, there was no hydrogen permeation, and no pitting. The concept of a generalized hydrogen embrittlement mechanism for stress corrosion cracking becomes increasingly attractive, since it is apparent that increased susceptibility to delayed failure under anodic potentials does not, per se, rule out the availability of hydrogen.