Cathodic protection of ship hull

The sacrificial anode method was applied to ship antisepsis in the 1940s.

Hull antisepsis

Hull anticorrosion, to prevent the corrosion of hull steel caused by the nearby atmosphere, sea water or river water, aquatic life and so on. There are two main ways to prevent hull erosion. The early used paint is a kind of oil coating, recently developed a new synthetic resin coating, service life can reach 3 ~ 5 years.

(1) Coating method: paint the hull steel surface, and use the paint film to isolate the corrosion of the nearby medium to the steel.

(2) Cathodic protection: the method of protecting hull metals by using different electric potentials of different metals.

New synthetic resin coatings of chlorinated rubber, ethylene, epoxy and polyurethane are preferred for corrosion protection of ship hulls exposed to the atmosphere and waterline. The protection current is regulated by an automatic potentiostat. Impressed current cathodic protection was introduced in the 1950s to protect hulls. The allowed cathodic protection potential is 0.75 ~ 0.95 volts. The cathodic protection law and coating law are generally used in combination to prevent corrosion of hull in fresh water. Cathodic protection is divided into sacrificial anode and impressed current cathodic protection.

. This method is by the DC power supply through the protection anode to the hull of the protection current, so that the hull as a cathode to be protected. This method is to choose a more active metal (such as zinc, aluminum) or alloy (such as magnesium alloy) than iron installed in the underwater part of the hull as the anode erosion, zinc, aluminum, magnesium is more active than iron, through the electrolyte seawater will constantly release electrons into the hull, so that the hull as a cathode to be protected. This is a simple and effective traditional preservative method. The protective anodes are made of lead or silver alloys, or platinum-plated titanium, etc. and are arranged on the surface of the underwater section of the hull.