Abstract

The assessment and prediction of the future life of new infrastructure and the remaining life of existing, perhaps already corroding, infrastructure requires estimation of likely future deterioration of system strength and performance. This requires models for likely corrosion loss and for likely maximum pit depth. For reliability assessments such models should be probabilistic and allow for environmental influences and material properties. An overview will be given of recent research to develop high quality models based on fundamental characteristics of steel corrosion. The models are complex non-linear functions of time since it has been shown that the controlling corrosion process changes from initiation to oxidation to bacterial-influenced corrosion. A constant ‘corrosion rate’ as commonly assumed by engineers is seldom valid and can be very misleading. The model applies to marine immersion, tidal, splash and coastal atmospheric corrosion. For immersion corrosion the effects of water temperature, dissolved oxygen levels, nutrient pollution, depth, water velocity and water salinity are reviewed and the effect of small changes in steel composition outlined.