Antifouling paint is a kind of paint used to prevent marine organisms from adhering, eroding and fouling, and to keep the immersed structures such as ships, docks and sonar clean and free of objects.It is composed of paint, poison, pigment, solvent and additives.It is coated on the antirust primer, and the poison in the paint slowly seeps outfilmMarine organisms, such asBarnacle, limestone, etc.[1]Antifouling coatings can be divided into contact type, dosage increasing type, diffusion type and self throwing type, which are mainly used in ships, marine structures, pipelines and other antifouling projects in seawater and fresh water.[2]
Marine biological fouling is ubiquitous in the marine environment, which is the most important problem faced by the shipping industry.According to research, there are as many as 2000 kinds of common marine fouling organisms, the most common ones are algae, hydra, barnacles, oysters, etc. Their attachment has caused great harm to ships and marine facilities, and seriously hindered the development of marine economy.The adhesion of marine organisms will lead to the increase of hull weight and navigational friction, the increase of power and fuel consumption, the blockage of marine pipelines and the failure of marine instruments.The cost of ocean transportation has quadrupled in the past three decades, bringing serious losses to world trade and maritime trade.[3]
So far, the application of marine antifouling coating is still the most economical and effective measure to prevent marine organisms from adhering. Therefore, the ship bottom needs to be coated with antifouling coating.
Chinese name
Antifouling paint
Foreign name
Antifouling coatings
Mainly used for
Ships in sea water and fresh water
Type
Contact type, booster type, diffusion type, self throwing type
1. Prevent the attachment of marine attached organisms within a certain period of time;
2. Poisons in the paint film steadily and gradually seep out to the sea water;
3. The paint film has certain water permeability to ensure the continuous leakage of toxicity;
4. Andanticorrosive paintGood adhesion and matching performance, antifoulingcoatingIt should also have good interlayer adhesion and be slightly soluble with antirust paint.
5. The paint film shall have good seawater impact resistance, and shall not bubble or fall off when immersed in water for a long time;
6. During navigation, it has different degrees of self polishing ability;
7. It has good storage stability, generally 1 year, and its antifouling performance does not decline during storage.
development history
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Two thousand years ago, wooden hulls were used, and people used thin lead plates to cover the hull to protect the bottom of the ship.In the 3rd century BC, the Greeks covered the hull with tar, wax and lead, and the Romans and Greeks protected the lead covering with copper nails.In the 5th century BC, people coated the bottom of a ship with a mixture of arsenic, sulfur and oil.From the 13th century to the 15th century, asphalt was widely used for the protection of ships, sometimes mixed with oil, rosin or tallow.In the 17th century, copper plates were used as antifouling materials.In the 19th century, with the emergence of steel hulls, due to the accelerated corrosion of copper on steel hulls, the antifouling technology of coated copper plates was finally abolished.Since people realized the inhibition of copper on marine organisms, the history of making antifouling coatings with copper as the toxic material began.In the middle of the 18th century, based on the idea of releasing poisons in polymer media, different kinds of antifouling coatings were developed.Copper oxide, arsenic and mercury oxide were the most popular antifouling agents at that time.Solvents include turpentine, naphtha and benzene.Linseed oilShellac varnish, tar and various rosins are used as base materials.Based on this mechanism, the US Navy has successfully prepared a cheap antifouling coating, which has an effective period of 18 months.In the mid-1950s, organotin as a toxic material began to be used in antifouling coatings;In the early 1960s, antifouling coatings containing organic tin had been commercialized, and this spectral insecticide existed in the coatings in a free form;In the 1970s, organic tin with long antifouling period appearedSelf polishing antifouling paintTBT-SPC，Its antifouling validity period is generally 5 years, and soon became the mainstream product of antifouling coatings.[4]
Akzo NobelIts international paint has upgraded and expanded its antifouling paint product lineup.The new product has a higher volume of solids, which means that the number of each matched coating can be reduced, and the over spraying and volatile organic compound emissions can also be reduced.The upgraded product portfolio is highly cost-effective in operation, as well as excellent environmental protection and performance advantages, thus helping shipowners, operating companies and shipyards cope with the challenges brought by the fluctuation of oil prices and increasing environmental pressure.
Paint type
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Traditional antifouling paint
This antifouling coating is based onrosinBased on adhesive, mainly usedCuprous oxideAs pigment.The rosin binder will dissolve and release toxic pigments when it meets with water.The problem with such antifouling coatings is that the decomposition of rosin adhesive is difficult to control and more serious.It's rightoceanThe protective effect of dirt can only last for 12-18 months.The rosin based antifouling coating will react with oxygen, so the paint must be put into water after drying - generally within 6-8 hours, but not more than 24 hours.This antifouling coating is also called soluble matrix antifouling coating.
Disadvantages: The antifouling period of this coating is short, only about one year.
Release antifouling coating
This kind of paint is based onChlorinated rubberOr ethylene is used as adhesive, and a large amount of cuprous oxide is used asPigment。In case of water, toxic pigments are released, leaving only the empty shell of adhesive.After a long enough time, the thickness of the empty shell will become very thick, so that the toxicity of the toxin released into the thin water layer is insufficient, which is lower than the critical value necessary to avoid the growth of pollutants.A large amount of toxic pigments will remain inside the antifouling paint system under the empty adhesive shell. People have tested the method of removing the empty adhesive shell by underwater brushing.Due to the problems of manpower, equipment management and inspection, this method is not effective.Before re construction of antifouling coating, the empty adhesive shell on the ship entering the dry dock must be sealed. When the number of times entering the dry dock reaches enough, a thick "sandwich" system consisting of antifouling coating and sealing coating alternately will be formed on the ship hull.When the total dry film thickness is 1000-1200 μ m, such sandwich system will generate large internal stress and peel off, resulting in very rough underwater shells.The release antifouling coating can protect marine pollutants for 18-24 months.This antifouling coating is also called insoluble matrix antifouling coating.
Disadvantages: After the toxic material is dissolved, the coating surface becomes rough, reducing the ship's navigation speed, and the ineffective antifouling coating is not easy to remove.
Ablative antifouling coating
This antifouling coating is based on an adhesive made from a mixture of rosin and a blended adhesive such as ethylene.The pigment used is also cuprous oxide, plus a small amount of otherBiological insecticide。Essentially, the mechanism of ablative antifouling coating is similar to that of pure traditional antifouling coating based on rosin, but the addition of blending (or wetting) adhesive prolongs its decomposition process.The dissolution of adhesive avoids the accumulation of sandwich system to a certain extent, but there is a very thin saponified layer on the surface of ablative antifouling coating, and the composition of adhesive shell structure on the surface is similar to that of release antifouling coating.Ablative antifouling coating can resist marine pollution for 26-30 months.
Self polishing antifouling paint
On the marketSelf polishing antifouling paintThere are two types: tin containing type and Wuxi type (tin free).The tin containing type uses tributyltin methacrylate as the adhesive.In addition to tin, toxic cuprous oxide is also the main pigment of paint, and other biological pesticides are often used to enhance the effect.The hydrolysis of its adhesive has long been described, but it must be pointed out that the self polishing antifouling coating will not accumulate to form a sandwich system.The self polishing tin containing antifouling coating can resist marine pollution for more than 5 years during navigation.The Wuxi type self polishing antifouling coating adopts an adhesive designed to simulate the action mechanism of tin isobutyrate adhesive.Wuxi self polishing antifouling coatings on the market include the following types:
·Zinc acrylate adhesive
·Zinc carboxylate adhesive
·Copper acrylate adhesive
·Silanized acrylic adhesive
The main mechanism of all the above technologies is hydrolysis and ion exchange.The polymer itself is hydrophobic because it is bound to functional groups through an ester bond.This means that when the polymer is immersed in seawater, the ester bond will be broken, leaving carboxylates to improve the hydrophilicity of the polymer.
Self releasing antifouling paint
This kind of antifouling coating is completely non-toxic, and works on the principle of low surface energy, that is, it is difficult for marine sewage tissue to adhere to the coating surface.This kind of antifouling coating is sometimes called dirt release antifouling coating, most of which are based on silicone adhesive.The unique surface properties of self releasing paint minimize the adhesion of dirt tissue.All dirt that may adhere can be easily (relatively speaking) washed away during operation or when entering dry dock.
The above types of antifouling coatings are mainly used for high-speed ships, such as ferries, container ships, yacht flights, ro ro ships, etc. Most paint suppliers stipulate that the above antifouling coatings shall not be used for ships with a speed of less than 18-20 knots.Nevertheless, there are indications that the minimum ship speed level can be further reduced (as low as 14-15 knots).Manufacturers are very cautious in specifying the effective service life of silicone based antifouling coatings. However, there is also a statement that "we have no reason to limit the service life of such materials".
Paint standard
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In order to reduce the impact of marine antifouling paint on the environment and human health in the production and use process, the Ministry of Environmental Protection recently issued the standard of Technical Requirements for Environmental Labeling Products Marine Antifouling Paint for the first time.
This standard has made requirements on the prohibited substances, limits of harmful substances and instructions for use in marine antifouling paint, and has stipulated the terms and definitions, basic requirements, technical contents and inspection methods of environmental marking products of marine antifouling paint, which is applicable to all kinds of marine antifouling paint.
This standard lists the prohibited substances in marine antifouling paint, including six categories of specific prohibited substances, including glycol ether and its esters, alkanes, ketones, halogenated hydrocarbons, alcohols, and silicochloric acid (asbestos).It also clearly stipulates the limits of volatile organic compounds (VOC), toluene+xylene+ethylbenzene, benzene, soluble heavy metals and other harmful substances.As for the active substances in marine antifouling paint, the standard clearly stipulates that DDT and mercury are prohibited. At the same time, it specifies the total content of tin and the rate of copper ion leakage (stable state). It requires that the active substances in the products should be low-risk substances, and lists them,Enterprises are required to evaluate the use of active substances not included in the list.[5]
Development prospect
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The development of environment-friendly antifouling coatings ismarine antifouling coating The direction of development.An antifouling coating with excellent performance should have the advantages of good antifouling effect, long effective antifouling period, economy, and little impact on the environment.With the research of new antifouling coatings and the development of supporting application technology, the practical application of these environment-friendly antifouling coatings will be in the near future.[4]
