O dimensionamento da proteção catódica em uma embarcação: estudo de caso

Abstract

The shipbuilding industry constantly faces the challenge of corrosion in ships, boats and yachts due to the electrochemical interaction between the hull metal and the marine environment, which is highly corrosive. Seawater is rich in dissolved salts and acts as an excellent electrolyte, which facilitates the formation of corrosion cells. To mitigate this process, methods to combat corrosion are used. In vessels, anti-corrosive coatings (paint) are applied to the external region of the hull together with cathodic protection, where both complement each other, ensuring more efficient protection against the corrosion process. This study aimed to size the amount of sacrificial anodes in a vessel under construction at the shipyard located in the state of Ceará. Based on bibliographic studies, the sizing steps were identified, which aim to transform the metal surface into a cathodically protected region. To this end, the metal structure to be protected is transformed into an artificial cell, to which an electric current flow is applied. This flow is generated by the potential difference between the metal to be protected and another metal, chosen as the anode, which has a more negative potential, according to the order of the oxidation potentials of the metals. With the calculations performed, it can be determined that the total current released by the anodes was 9 A, which is higher than the current required for protection, 2.88 A, therefore, the surface is cathodically protected. To distribute the protective current flow, 20 zinc anodes were used, evenly distributed to ensure protection of the entire submerged surface. It can be concluded that, even in the aggressive conditions of the marine environment, with adequate and correctly executed sizing, the cathodic protection system is capable of significantly reducing the effects of corrosion on the metal structures of vessels.