Although titanium alloys have good corrosion resistance in seawater, the surface of the alloy is prone to grow marine animals, most of which are lime worms, algae and a small amount of oysters. After removing the marine organisms on the surface of the alloy, it was found that the surface of the titanium alloy was not corroded, which means that marine organisms and microorganisms would not cause corrosion to the titanium alloy. Therefore, preventing the blockage of titanium alloy pipes only considers how to prevent marine organisms from adhering to the surface of titanium alloys.
There are several ways to prevent titanium and titanium alloys from marine animals such as layer filtration, heating, sealing or ozone and ultrasonic antifouling. Today we will introduce three types of coatings to prevent blockage of titanium alloy pipe used in marine.
Low Surface Energy Coating
The surface energy of the coating determines the adhesion strength of the sea creature on its surface. The lower the surface energy of the coating is, the more difficult the biological attachment is. Even if it is attached, the adhesion strength is not large. When a ship coated with a low surface energy coating is started at a certain speed, the sea creature attached to its surface will automatically fall off. Low surface energy antifouling coatings are not toxic and have a long shelf life, which is an important substitute of toxic antifouling coatings.
However, low surface antifouling coatings have not been widely promoted in the US Navy mainly because of the following three factors:
1) the high cost,
2) the strict construction requirements, and
3) it is easy to be damaged.
Conductive coating antifouling technology is a more advanced environmentally friendly antifouling technology, which has no pollution to seawater environment. The principle is to apply an insulating coating on the steel plate in contact with seawater, and then apply a conductive coating on it. By using this coating film as an anode and then applying a small current, seawater is electrolyzed on its surface. The surface of the conductive coating film is covered with hypochlorous acid ions, and it can avoid the adhesion of marine organisms such as microorganisms, algae, and shellfish.
Natural Bionic Coating
- Natural synthetic antifouling coating
Marine animals, plants and microorganisms themselves have an anti-fouling mechanism. Therefore, natural products (natural bio-antifouling agents) can be extracted from these creatures, and can be then prepared into natural synthetic antifouling paints by self-polishing techniques. The study of natural antifouling agents is the key to the synthesis of natural antifouling coatings. By 1993, 52 antifouling active substances had been found in marine organisms. It is expected that new antifouling agents will be discovered from more than 6,000 active substances isolated in the future.
- Biomimetic coating
Most of the creatures living in the ocean, especially large mammals such as dolphins and whales, have the effect of resisting the attachment of sea creatures. Their epidermis secretes special mucus to form a hydrophilic low surface energy surface, making it difficult for marine organisms to adhere. Non-toxic biomimetic coatings can be developed according to the study of the mechanism of the anti-bioadhesion of these large mammals.
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