ABSTRACT:

This paper proposes an optimum arrangement method of Al galvanic anodes for a cathodic protection on offshore structures when environmental factors on the cathodic protection are parametrically changed. In order to propose an optimum arrangement method of Al galvanic anodes for the cathodic protection, a partially small scale model of a cathodically protected offshore structure was experimented at first. In the experiment, potential distributions were measured according to the parametric change of the flow rate and the conductivity of experimental solution and the distance from the water surface to Al galvanic anodes. Next, the experimental model was analyzed with 3D FEM. The calculated potential distributions were compared with those obtained from the experiment and it was confirmed that the calculated results agreed well with experimental ones. Then the potential distributions of a 1000 m long floating airport were analyzed with 3D FEM when the flow rate and the conductivity of seawater were parametrically changed. The calculated results showed that the relation between the polarization parameter and the distance among Al galvanic anodes was almost linear in the logarithmic coordinates, and an optimum arrangement method of Al galvanic anodes for offshore structures was proposed based on the obtained relation.

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