Abstract
The underwater electric potential (UEP) signature is an electric signal, which can be exploited by naval mines to be utilized as a possible trigger indicator and may cause severe damage to the vessel and the onboard crew. Hence, knowing the UEP signature as exactly as possible can help to evaluate a possible risk of the vessel being detected by naval mines or if the UEP signature is within a noncritical region. As the UEP signature differs for changes of the corrosion protection system, the UEP signature is usually unknown for new conditions. In this work, we present a simple mathematical formulation to predict the UEP signature based on the mere use of a single reference UEP signature, and the corresponding currents, which are excited by the impressed current cathodic protection (ICCP) system. With this methodology, deviations below 10% between the maximum of the simulated UEP signature and the predicted UEP signature can be achieved, even in the presence of the nonlinear corrosion process. Furthermore, a corrosion protective coating of the propellers can significantly reduce the influence of the nonlinear corrosion process on the total UEP signature to improve the prediction accuracy of the superposition formulation as presented in this work.
Highlights
In the fabrication process of naval vessels, different metallic materials are used
This lower demand of impressed current cathodic protection (ICCP) current leads to major reductions of the underwater electric potential (UEP) signature, which is beneficial to lower the risk of possible detection of the vessel, as well as suppressing the nonlinear corrosion process, with the latter aggravating the superposition formulation of UEP signatures
When applying the HY-80 steel polarization curve for the hull and sea chests including a coating damage of 5% for the hull and 10% for the sea chests a maximum deviation of 10% between the simulated UEP signature and the predicted UEP signature was achieved, which can be considered as an accurate prediction result
Summary
In the fabrication process of naval vessels, different metallic materials are used. When these materials are galvanically connected and placed inside the seawater an electric current density will occur, which flows from the less noble metallic material to the more noble metallic material through the seawater. In case of the SACP system a material less noble (in comparison to the hull) is galvanically connected to the hull, protecting the hull from corrosion while enforcing the hull material in the cathodic regime, while the oxidation process from (1) at the sacrificial anodes is present. Each system is capable of protecting a naval vessels’ hull from corrosive damage but the main drawback of these systems lies within the additional current density, which is generated by the corrosion protection system itself This current density causes an additional electric field, which may increase the total UEP signature of the naval vessel. The presented methodology helps to estimate the risk of possible vessel detection for various materials when the ICCP currents change and improve the understanding of nonlinear corrosion processes for different metallic materials
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