ISO 20313:2018 specifies protection criteria, and makes recommendations for design and specifications for both impressed current and galvanic anode cathodic protection systems for ships. Cathodic protection of external hull and ballast tanks are included.

ISO 20313:2018is applicable to the immersed sections of hulls and tanks containing seawater for ships, boats, and other self-propelled floating vessels. It includes fixtures generally encountered on ship hulls such as:

- rudders;

- propellers;

- shafts;

- stabilizers;

- thrusters;

- sea chests;

- water intakes (up to the first valve).

ISO 20313:2018 does not cover protection of floating structures that are not self-propelled.

ISO 20313:2018 is applicable to the cathodic protection of ship hulls fabricated principally from carbon manganese or low-alloy steels including fixtures of other ferrous or non-ferrous alloys such as stainless steels and copper alloys, etc.

ISO 20313:2018 is applicable to both coated and bare hulls and tanks; most hulls and tank internals are coated.

ISO 20313:2018 is not applicable to the cathodic protection of hulls principally made of other materials such as aluminium alloys, stainless steels or concrete.

ISO 20313:2018 is applicable to the hull and fixtures in seawater and all waters which could be encountered during a ship's world-wide deployment.