Establishing an atlas of risk of pitting of metals at sea – demonstrated for stainless steel AISI 316L in the Bass Strait

Abstract

Pitting and corrosion of metals at sea is a major problem, especially with offshore equipment that is required to process oil and gas 24h a day. Although pitting is reasonably well understood, initiation due to naturally occurring random, fluctuations in sea temperature and salinity has not been reported. This represents a potential risk. Here we apply the probabilistic method of Davey et al. (2015) (Chem. Eng. Sci. 126, 106–115) to quantitatively predict this risk and use it to create a new map for metals pitting at sea. We devise isorisques that we propose as contours of equal probability of risk of pitting drawn on a map. We demonstrate these for stainless steel (AISI 316L) in the Bass Strait. We explain how replication for other regions and metals could establish a new, manifold atlas of world pitting risk. The atlas, refined, will be a predictive guide to improve metals selection and corrosion mitigation, and to compute pitting risks with changes in sea surface temperature and salinity. The atlas in digital form could be updated in real time to reflect significant climatic events. The illustrative map and idea for a world atlas will be of interest and benefit to a wide readership in chemical engineering materials selection and construction. The atlas could be iteratively refined to include pipe-roughness and other appropriate features.