The stress corrosion cracking (SCO) susceptibility of an experimental, as-rolled, dual-phase steel was investigated in 0.5 M Na2CO3 – 0.5 M NaHCO3 solution at various potentials and temperatures by constant extension rate tensile (CERT) tests. A commercial API X-65 pipeline steel with similar mechanical properties was tested in the same way and the results compared.
It was found that the dual-phase steel is less susceptible to SCC than the X-65 pipeline steel in the critical potential range above the primary passivation potential. Briefly-exposed, metallographically-polished dual-phase steel samples were observed to be selectively attacked at the martensite phase in the critical potential range, but since the martensite phase is not aligned in any way, there is no susceptible cracking path. For both steels, a considerable amount of deformation is required before hydrogen embrittlement occurs.
