Uncertainty in corrosion wastage prediction of oil tankers

The paper describes investigation of the global and local corrosion wastage of three single-hull oil tankers built in eighties. Analysis of data is based on existing thickness measurements of hull elements from Croatian Register of Shipping (CRS) file, gauged on periodic dry-docking and close-up surveys of ships in service after 10, 15 and 20 years. Hull Girder Section Modulus (HGSM) and local corrosion wastage of main deck plates and longitudinals are determined as a function of time taking into account the lifetime of the protective coatings. The available theoretical non-linear corrosion propagation model is fitted to the measurements after 10 and 15 years in order to predict the corrosion loss at 20 years. Uncertainty of the corrosion propagation model is then determined by the statistical analysis of differences between predicted and measured corrosion losses at 20 years.