Characterising the early stages of crack development in environment-assisted cracking

Abstract

ABSTRACTAn overview is given of recent NPL research to characterise the early stages of crack development in environment-assisted cracking, focusing on the nature of the crack precursors, the pit-to-crack transition, and the impact of solution chemistry on growth rate in the small and long crack growth rate regime. The impact on corrosion and cracking of surface grinding-induced changes in near-surface material and mechanical properties is highlighted, noting that awareness of this aspect in the corrosion community still remains limited. A major feature is the remarkable insight into the evolution of small surface cracks, from dealloyed layers and from corrosion pits, provided by advanced 3D imaging. Finally, further evidence for the concept of the solution conductivity-dependent crack-size effect in stress corrosion cracking and corrosion fatigue is put forward.