Cathodic protection modelling of a propeller shaft

Current and potential distributions on a stainless steel propeller shaft protected by galvanic anodes were investigated by means of Finite Element Method (FEM) modelling. The effect of seawater flow and shaft rotation was evaluated. The results of simulations are compared with experimental measurements performed on steady shaft in natural seawater. Modest polarization can be noticed in all operating conditions, not sufficient for preventing biofilm action on localized corrosion initiation. Only in stagnant conditions, without any water renewal, the consumption of oxygen leads to an appreciable potential decreasing to match the limits of normal protection indicated in the European standards.