Effect of environmental factors on steel plate corrosion under marine immersion conditions

This study considers different environmental factors affecting corrosion under marine immersion conditions and proposes a mathematical model incorporating their effects on corrosion degradation through the ship life. The study adopts a nonlinear function of time as the reference corrosion model calibrated with operational corrosion data at long term average conditions to represent the corrosion behaviour under standard environmental conditions. Based on previously obtained field data, a corrosion deterioration model is developed, in which a correction factor is proposed to account for the effect of each environmental factor. These multiplicative factors correct the standard prediction of corrosion degradation to obtain short term estimates under any specific environmental condition. Then, a long term estimate of corrosion degradation is determined by summing the short term corrosion contributions during the various discrete time periods in which the ship life can be decomposed. A numerical example of a representative application of the new empirical based corrosion model is presented, to demonstrate how to apply the model.