Long-term corrosion of cast irons and steel in marine and atmospheric environments

Long-term corrosion trends are important for assessing the remaining life of critical infrastructure. Herein the available literature data for grey cast iron and cast steel exposed to marine and to some atmospheric environments are shown to be consistent with the bi-modal model previously developed for steels. However, the development of the second mode takes longer. This is proposed as resulting from the graphitized zone slowing the diffusion of species controlling the longer term corrosion processes. A practical simplified model and its parameters are proposed.

► Longer term corrosion of various cast irons shows a bi-modal trend with exposure time.
► This applies for marine immersion, tidal and freshwater and for atmospheric corrosion.
► Proposed as resulting from pitting under anoxic conditions under corrosion products.