Corrosion wastage model for ship crude oil tanks

This study investigates the effects of temperature, carbon dioxide and hydrogen sulphide concentrations on the corrosion behaviour of ship steels subjected to crude oil tank atmospheres. A new corrosion wastage model is proposed based on a standard non-linear time dependent corrosion model modified by the effect of the different environmental factors contained in the crude oil tank atmosphere. The new corrosion model assesses the corrosion degradation under stationary environmental conditions denoted as “short-term”. The long-term corrosion degradation is assessed by considering the succession of the various environmental conditions that can be present in the tank and adding the corrosion damage incurred during each of them. Corrosion records depending only on time are used to calibrate the standard model while the effect of environmental factors in increasing or decreasing the corrosion rate is based on formulations published by other authors. A numerical example of a representative application of the new corrosion model is presented, to demonstrate how to apply the model.