The bottom painting is mainly to prevent the shells and insects on the seabed from adhering to the bottom of the ship, reduce the corrosion of the ship shell by seawater and prevent rust. After painting, the steel is isolated from seawater and the corrosion rate slows down. Bottom painting is a kind of paint painted below the waterline of the ship and immersed in the underwater bottom for a long time. These paints are generally red, so the bottom of the ship is mostly red.
There are all kinds of marine animals in the sea. Some of them, such as oysters and sea anemones, like to grow on the surface of various underwater objects. The bottom of the ship is also a very good environment. Although it is small, it increases the weight of the ship, affects the smoothness of the bottom shell and increases the resistance during navigation. Some toxic substances are added to the antirust paint applied to the bottom of the ship, so that marine organisms will not grow in these places, so that the bottom of the ship can be kept clean for a longer time.
When a large ship loaded with goods sails in the sea, it is necessary to take into account the different specific gravity of sea water. For example, a ship sailing in the sea with a large proportion carries a lot of goods and has a deep draft. Once it sails to the sea with a small proportion, it will suffer less floating water, which will deepen its draft. If it encounters big storms and waves again, it may be dangerous.
In order to ensure safety, all kinds of ships have signs of ship load, which is called "waterline" as the saying goes. The following is the ship load mark stipulated by China's Ship Inspection Bureau. The marks respectively indicate that R (T) represents the tropical load line.