Development of new applied models for steel corrosion in marine applications including shipping

Models for the prediction of corrosion often give the misleading impression that corrosion of steel in seawater environments is a linear function of time (the "corrosion rate"). More recently non-linear functions for corrosion loss have been proposed calibrated to aggregated data from a wide variety of sources. Unfortunately, this use of the data produces models with wide ranges of uncertainty and makes it difficult to predict future corrosion and to assess the effect of steel composition and environmental influences. Recent research has produced a model based on the fundamental characteristics of steel corrosion, including the effect of biological influences. Detailed investigations show that the process controlling the (instantaneous) rate of corrosion changes as corrosion progresses. This is represented as a sequence of phases for which fundamental theoretical justifications and mathematical relationships have been derived. To ensure the model has practical validity, it has been calibrated to carefully selected actual field observations. This has also allowed the effect of water temperature, dissolved oxygen levels, nutrient pollution, depth, water velocity, water salinity, and steel composition to be isolated, as reviewed briefly herein. Some observations about applications and research directions are given.