This article follows Part 2 of this series discussing the different parts of the hull. We will discuss the different technologies of antifouling paints used to protect the hull.
The philosophy of formulating antifouling paints rely on its ability to avoid the build-up of marine growth on a ship’s hull. It is important to avoid marine growth because the growth adds drag to the ship as it slides against the water surface, the smoother the surface, the lesser the drag. Some technologies involve:
These coatings render the hull hydrophobic working on the slipperiness of the surface of the finished coating. Because of this, the glue that makes marine growth holdfast to the surface of the coatings will simply slough off during normal trade of the vessel.
On the other end of hydrophobic coatings come hydrophilic coatings, the principle is that the surface likes water so much it prevents marine organism to take hold of the surface. This approach is quite new in the development of marine coatings.
This is a more conventional approach to antifouling paints. Many marine coatings manufacturers use this approach in formulating their antifouling paints.
A biocide is embedded in a resin structure that is slightly soluble in water. As long as a fresh layer of biocide is exposed to the surface of the antifouling paint, marine growth will have a hard time proliferating.
The trick is how to control the polishing rate of the resin structure to expose enough of the biocide to kill marine growth. This type of antifouling will polish or erode over time.
Epoxy coatings are still used for ship hulls that do not trade in open water or for vessels that intermittently go into fresh/brackish water and seawater.
Not all marine growth will survive being outside saltwater for too long, barnacles, mussels, oysters cannot survive outside a seawater environment for so long. Normally vessels that do not need to go deep-sea trading does not antifouling paints as part of a marine coatings system.