Probabilistic Model of Pitting Corrosion and the Simulation of Pitted Corroded Condition

Pitting corrosion is a great concern with respect to the integrity of ship hull structures such as the hold frames in way of the cargo holds of those bulk carriers which exclusively carry coal and/or iron ore. The actual strength of pitting corroded member depends on the pitting corroded surface condition; a condition which varies according to the generation and the progress of the corrosion pits. In order to investigate a practical strength evaluation method of the pitting corroded member, a serial strength evaluation for various pitting corroded conditions is necessary. However, because it was difficult to obtain actual pitting corroded members which satisfied the purpose of our analysis, we needed to use an alternative method of conducting this strength analysis; a method that used simulated pitting corroded members. In order to do this, the simulated pitting corrosion surface we used had to have been a good representation of the actual pitting corrosion condition. In this paper, we investigated the pitting corroded surface conditions of hold frames in way of cargo holds of bulk carriers in order to comprehend the statistical nature of such pitting corroded surface. We developed a simulation procedure based upon a probabilistic model and used it to generate an optional pitting corroded surface. Through our investigation, we were able to confirm that the simulated pitting corrosion condition is visually similar to the actual condition and has the same statistical nature.