We present here an original method to search the corroded zones of an underwater steel structure. Nowadays, after a defined navigation period, a vessel is placed in dry dock, to examine its hull state, find the damaged areas and then paint them. This step of identification, very long and relatively inefficient, could be replaced by a series of electrical measurements which would be processed to get clues about the state of the hull. Those results are obtained thanks to the study of the cathodic protection system equipped on the hull. This new method allows a great timesaving but also a precision never reached before.

We present here an original application linking an electrochemical phenomenon and the computational aspect of electromagnetic fields to provide a corrosion diagnosis of a protected underwater steel structure. This is done with the pairing of a boundary element method and the resolution of an inverse problem. After a defined operating time, it is mandatory to check an underwater steel structure. Sadly, current examinations techniques require immobilizing the structure for a long time and are less efficient. The purpose of this paper is to replace this checking by a series of close electrical measurements in the conducting water which provides a corrosion diagnosis of the structure. The new method introduced ensures great time-savings but also an accuracy never reached before. This paper presents this numerical method and its checking through real electrical measurements on a frigate mock-up. Index Terms-Boundary element method (BEM), cathodic protection, inverse problems, regularization techniques.

No abstract