It is well known that the harsh corrosive environment of the ocean has a very important impact on the operational life and navigation performance of the ship. In order to minimize the corrosion of hull materials, the ship has adopted various protection methods from design to manufacture, such as hull coating protective coating, sacrificial anode or electric anti-corrosion, and the use of hull materials with strong corrosion resistance. Among them, coating anti-corrosion coating is the most extensive and convenient means of protection.
Development status of marine coatings
According to the corrosion situation of the ship and the different requirements of the protective performance of various parts, after years of practice and application, marine coatings have formed their own systems, which are mainly divided into anti-rust primer, hull topcoat, fresh water tank coating, anti-fouling coating and Special functional coatings.
Marine anti-rust primer
Marine anti-rust primers are traditionally divided into interior paints and exterior paints according to the area of ​​use. In the past, chlorinated rubber systems were generally used as anti-rust primers for shipbuilding, and asphalt primers were generally used as protection for areas with severe corrosion conditions such as waterline below and ballast tanks.
According to the performance, the chlorinated rubber primer has the advantages of excellent coating performance, good coating film formation and overcoating, and is relatively inexpensive, so it has been widely used. However, chlorinated rubber primers can only be used as a low-grade coating because of their aging and toxic shortcomings. Most of them are currently replaced by acrylic primers and epoxy primers, and are used only in small quantities on ship repairs. With the development of technology, today's modified epoxy coatings have a comprehensive trend to replace rust-proof primers, and pure epoxy primers with superior performance are also widely used by new shipbuilders.
Due to the pollution of asphalt to the marine environment, from the late 1990s, the use of epoxy asphalt coatings as anti-corrosion coatings has been basically banned internationally. Internationally, asphalt coatings and tar epoxy coatings have been basically discontinued. However, due to the excellent anti-corrosion performance of asphalt and the strict requirements of domestic regulations, domestic manufacturers are still producing related products.
2. Hull finish
The hull topcoat is divided into waterline paint, dry lacquer, deck paint and interior finish.
In the past, traditional shipbuilding usually used chlorinated rubber topcoat as the outer paint. However, due to the inherent shortage of chlorinated rubber topcoat, it was gradually replaced by acrylic topcoat. Acrylic topcoats are less prone to pulverization. In recent years, new shipbuilding has been used less. Now, shipbuilders generally use epoxy topcoats and polyurethane topcoats. Polyurethane topcoat has many advantages such as high hardness, good color and strong gloss retention, and it has gradually become the leading product of hull topcoat.
3. Fresh water tank coating
Coated cement is a protective measure for traditional shipbuilding freshwater tanks. The use of cement protection has almost no impact on water quality, but cement has the disadvantage of many voids and easy cracking, and the protection against corrosion of steel plates is not satisfactory. In modern shipbuilding, freshwater tank paint is commonly used for the painting of fresh water tanks.
Freshwater tank coatings are currently commonly used in pure epoxy coatings, with high solids and solventless epoxy coatings. The latter require high levels of equipment and technology, and small cabins are rarely used. At present, from the point of view of use, there are widespread construction difficulties and incomplete odor removal. The water quality of freshwater tanks is not greatly improved, and it is most difficult to reach drinking water standards as domestic water.
High-grade fresh water tank coatings are currently produced in less domestic quantities and generally require imports. Not only the delivery period is long, but also the construction conditions of high-grade coatings are harsh. The requirements for ambient temperature, humidity, ventilation conditions, descaling level, and spraying equipment are high. Small and medium-sized shipyards use high-grade fresh water tank coatings even if they are constructed according to shipowners' requirements. It is difficult to achieve the performance requirements of the coating.
4. Antifouling paint
In order to prevent the marine body from attaching to the hull and causing biological corrosion and affecting the speed of the ship, the underwater part of the hull generally adopts antifouling paint to inhibit the development of marine life. Traditional antifouling coatings use marine arsenic, cadmium, lead, and tin compounds to kill marine organisms. However, these compounds eventually enter the human body through the enrichment of marine organisms, seriously endangering human health. At present, the International Maritime Organization has issued a "blocking order."
At present, the antifouling coating used on ships is an antifouling coating using cuprous oxide as an antifouling agent, which is divided into a long-acting antifouling coating and a self-polishing antifouling coating. The former must be launched as soon as possible after construction, otherwise it will crack, and the latter will not have these restrictions. From the perspective of use, long-lasting antifouling coatings are suitable for use in ships and offshore facilities where the sailing rate is not high, while self-polishing antifouling coatings are suitable for ships with relatively fast speeds and high sailing rates. Since cuprous oxide is still toxic to humans, it is only allowed to exist as a transitional product in the world, and will be gradually banned in the future. The development of a new generation of antifouling coatings has achieved initial results, but from the point of view of listed products, there are widespread shortcomings such as high price, difficult construction and narrow use range, and it is difficult to adapt to the requirements of large-scale shipbuilding.
5. Special function coating
Special functional coatings have emerged with the deepening of the ship market, including oil tank coatings, fire retardant coatings, chemical tank coatings and high temperature coatings. These coatings are custom produced in most cases depending on the specific conditions of the cabin and the load.
The special coatings currently in common use are mainly produced by using epoxy resin as a matrix to add special requirements additives (such as oil-resistant pigments of oil tanks). For example, general-purpose temperature-resistant coatings use aluminum powder as an additive to achieve a certain temperature resistance; for harsh environments, special coating series are required, such as silicone paint as a high-temperature coating.
Nowadays, most of the marine coatings market is controlled by foreign companies, such as international coatings, Kansai coatings, PPG coatings and other large multinational companies; local companies only occupy a small share, such as Shanghai Kailin, Xiangjiang coatings, Jiangsu Jinling The only way for local companies to catch up with foreign companies is to “practice internal strengthâ€, increase scientific and technological research and development, and improve the training mechanism for scientific and technological talents.
[Follow the WeChat public number "Jiuzheng Paint Network"; pay attention to surprises, scan code to view "If your husband is selling paint..." Jiuzheng Coating Network Exchange Group]
Sealand is a trustworthy manufacturer of CNG Mass Flow Meter, CNG Mass Flowmeter, CNG Flow Meter, CNG Flowmeter, CNG Coriolis Meter, ATEX, IECEx & CE approved.
With its high accuracy, wide rangeability and reliable performance, Sealand meter has been applied in many kinds of industries during the last 8 years. Unlike others who only focus on the measurement of liquid at normal pressure & temperature, Sealand has conquered the difficulty in the measurement under severe conditions, such as high pressure, high viscosity, high & low temperature.
Take CNG (compressed natural gas) for example. As the saying goes, the meter can measure anything else if it can measure CNG. It is quite hard to measure gas under high pressure. The sensor must be able to bear high pressure; in this way, the thickness of flow tube must be increased, so the transmitter shall be more sensitive to detect the signal; however, Sealand made it. Sealand's first model is specially designed for CNG dispenser, and now thousands of this model are put into use on the market.
CNG Mass Flow Meter, CNG Mass Flowmeter, CNG Flow Meter, CNG Flowmeter, CNG Coriolis Meter
Zhejiang Sealand Technology Co., Ltd. , https://www.sealandflowmeters.com