The effect of environmental variables on early corrosion of high–strength low–alloy mooring steel immersed in seawater

Abstract

Traditionally, the designing of mooring lines has been aimed at fulfilling the mechanical strength criteria using standard theoretical models and simulation in wave tunnels. This approach has led to various critical failures since degradation of a mooring line under specific environmental and loading conditions, which depend on the locations of the off-shore platforms, were not properly considered. The purpose of this paper is to investigate into the effect of three environmental variables – temperature, salinity and dissolved oxygen – on the corrosion behaviour of two steel grades used for mooring chains and to develop an empirical model intended to link these variables with the corrosion rate. A full-factorial experiment was designed on the basis of the statistical analysis of the objective data on the ocean water conditions corresponding to nine regions of Atlantic, Indic and Arctic oceans. A practical uncoupled method to determine the corrosion rate of these steel grades as function of the water conditions was developed.