The application technology status and development analysis of marine engineering heavy anti-corrosion coatings

China Coatings Online News: Marine corrosion prevention is one of the key technologies of marine engineering, metal corrosion in the ocean caused by stress corrosion fracture (SCC), hydrogen brittle (HE), corrosion fatigue (CF), intercrystalline corrosion (IC) will cause sudden fracture of the offshore steel structure, resulting in ecological disaster of the marine environment, resulting in huge losses. In addition, the early failure of anti-corrosion coatings in offshore products and the down-work stopping losses caused by coating repairs are also considerable. Therefore, appropriate anti-corrosion techniques must be adopted to solve the problem.
years, more and more attention has been paid to marine corrosion and protection at home and abroad, although a variety of seawater corrosion-resistant materials have been introduced, a variety of anti-corrosion construction technology has also developed, but still far from meeting the actual needs. China's anti-corrosion research on marine engineering structure facilities and foreign developed countries have a clear gap, some key technologies have not been resolved, did not form a technology with China's independent intellectual property rights, and lack of corresponding anti-corrosion norms and standards, which seriously affect the design, construction and safe operation of marine engineering structure. Therefore, in view of the commonality and key corrosion prevention problems faced by key sea areas and major marine projects in China, it is of great significance to carry out long-term anti-corrosion key technical research on marine engineering structural facilities, which can not only prevent corrosion, avoid or reduce the maintenance, maintenance costs and economic losses caused by later service, reduce the occurrence of major malignant accidents, but also greatly improve the safety of offshore engineering facilities.
1 Marine anti-corrosion coatings are required marine anti-corrosion coatings that are used in the marine environment. Because the marine environment is very harsh and highly corrosive, marine corrosion prevention is an urgent and urgent subject in the development of marine engineering in China.
according to the anti-corrosion object material and corrosion structure, marine anti-corrosion coating can be divided into marine steel structure anti-corrosion coating and non-steel structure anti-corrosion coating. Marine steel structure anti-corrosion coating mainly refers to the transport of ships, containers, sea bridges, port machinery, pipelines, offshore oil platforms and other large-scale facilities of anti-corrosion paint, non-steel structure marine anti-corrosion paint mainly refers to marine concrete structure anti-corrosion paint.
Marine anti-corrosion coatings are mainly inorganic zinc-rich, organic zinc-rich, silicone, epoxy, acrylic, polyurethane, fluorocarbon, polysilioxane coatings, according to different marine environmental corrosion characteristics and anti-corrosion years to choose different coatings and coating systems. Marine anti-corrosion coatings generally require the following properties:
(1) have good physical properties. Good impermeability to corrosive media and good adhesion to steel surface;
(2) has good performance in engineering. Resistance to seawater flushing, sea ice collision, wear and tear of ship docking;
(3) has excellent chemical properties. Sea water resistance, salt spray resistance, oil resistance, chemical resistance, UV resistance and other erosion;
(4) is compatible with electrochemical protection systems. Splash zone and full immersion area coating should be cathode-resistant;
(5) has good construction performance. High-quality coating construction of different structures can be carried out under various environmental conditions.
(6) meet the requirements of health, environmental protection and safety. The coating is required to have a high solid content and the volatile organic compound (VOC) content meets the requirements of national or international standards;
(7) other special requirements. Such as: freshwater cabin coating requirements non-toxic and in line with national health certification requirements; The chlorine content of the coating used on the stainless steel surface should not exceed 200 mg/kg, and the coating does not contain zinc; Ship ballast cabin coatings should meet the requirements of the International Maritime Bureau (IMO) "Ship ballast cabin protection coating performance standards"; The coating of the part below the ship's waterline requires the prevention of attachment of sea creatures, etc.
main relevant international standards for marine heavy anti-corrosion coatings commonly used in china are:
(1) ISO 12944 protective coating system corrosion protection against steel structures;
(2) NORSOK M501 surface treatment and protection coatings;
(3) ISO 20340 offshore and related structural protective coating system performance requirements;
corrosion control of offshore structures by the protection coating of NACE SP O108 at the same time as the 4th.
(5) IMO Ship Ballast Cabin Protection Coating Performance Standard (PSPC).
marine anti-corrosion coatings and their coatings are typically required to meet the requirements of ISO 12944, NORSOK M501, NACE SPO108 and ISO 20340 related corrosion standards. Generally have to pass strict corrosion test and certification in advance, the main test projects are:
(1) salt spray resistance (salt water) test 4,000 h;
(2) cathode-resistant peeling test;
(3) wet-resistant heat test 4,000 h;
(4) cycle corrosion test 4 200 h.
2 Marine anti-corrosion coating research and development focus on marine anti-corrosion coating research and development with high scientific and technological content, long development cycle, large investment, technical difficulties and risk, foreign marine anti-corrosion coating research and development is mainly concentrated in the strength of large companies or government-supported departments. For example, the United Kingdom IP, the United States PPG, Denmark's Hemple, Norway's Jotun and Japan's Kansi coatings and other large companies have hundreds of years of relevant paint development history, in the paint production and supply, quality supervision, coating specifications and coating site management, etc. formed a set of very strict and strict system, the current products of these companies occupy the main market of China's marine anti-corrosion coatings.
China's marine anti-corrosion coating production is mainly concentrated in Qingdao, Shanghai, Dalian, Tianjin, Changzhou, Guangzhou and Xiamen and other coatings enterprises, research work mainly concentrated in the Chinese Academy of Sciences Institute of Oceanographic Research, chinese Academy of Sciences Institute of Metal Corrosion, Marine Chemical Research Institute, CNOOC Changzhou Paint Research Institute, China Shipping 725 and other research institutions. In recent years, although the establishment of "China's shipbuilding industry ship coating Xiamen testing station", "marine paint product quality supervision center" and other quality management supervision bodies, but the overall level of technology still lags behind advanced countries.
, the research and development of marine heavy anti-corrosion coatings abroad mainly focus on the following aspects.
2.1 long life due to more and more super-large steel structures and the characteristics of the sea area does not have the conditions for direct re-painting or back to shore construction, so the development of marine anti-corrosion coating with an ultra-long service life, ideally, the coating service life including on-site direct coating maintenance after the extended service life is equivalent to the life of steel structure equipment, that is, the coating and equipment with the same life design, use only a small amount of maintenance, weight-free coating.
Belgian coating galvanizing is an organic high zinc-rich coating with a 96% zinc content in the dry film, and in the coastal ocean atmosphere of Oslo, Norway, the average annual coating loss measured after coating a single zinc coating of 120 m thick on a steel bridge is only 1 m.
The most typical success story for inorganic zinc-rich coating applications is Morganwyalla's 250 km pipeline project in Australia, where corrosion protection uses a single-layer water-based inorganic zinc-rich coating, which remains in good condition for more than 50 years and is corrosion-free. Exxon's refinery on Sulphur Island uses a single-layer zinc silicate corrosion-proof coating, which requires only a small portion of the coating after 15 a and then 4 a.
as a paint, the current development of fluorocarbon coatings and polysilica coating weather resistance has reached more than 15 a, such as Japan's Asahi Nitro subsidiary production of TEFFEVE fluorocarbon paint, Dajin company produced Teflon FEVE fluorocarbon paint, international paint company production of acrylic polysilica coating 979 and the United States Cameron company produced PSX 700 and so on.
2.2 Low surface treatment because pre-coating costs will account for 60% of the total coating costs, so low surface treatment coatings have become one of the important research directions of anti-corrosion coatings. These include rusty, wet coated coatings and coatings that can be applied directly to other types of old coated surfaces. This kind of coating is mainly epoxy, they have the function of direct coating on the wet rusted steel surface, have super adhesion, VOC content of <340 g/L, a gas-free spray film thickness of more than 200 m, excellent construction performance.
2.3 high solids, solvent-free volume solid content of more than 70% for high solids coatings, solid content of 100% for solvent-free coatings. Because of the use of less or even no organic solvents, so that high solid sub-coating can reduce VOC emissions, in line with environmental requirements, and a single construction can obtain the required film thickness, thus reducing the number of construction channels, saving re-painting time, improve work efficiency. The pore rate of the coating is reduced due to solvent-free volatility, which improves the impermeability and corrosion resistance of the coating.
2.4 water-based coatings is another important aspect of coating research and development. Its low VOC content is of great significance to energy conservation and emission reduction, the development of low-carbon economy, environmental protection and sustainable development. At present, the research and development of water-based coatings is mainly in the water-based inorganic zinc-rich, water-based epoxy, water-based acrylic, water-based fluorocarbon system and other fields. Among them, the industrial application of water-based acrylic, water-based epoxy and water-based inorganic zinc-rich coating varieties has been successful to a certain extent. Asahi Nitro subsidiary of Japan has developed a new low VOC water-based FEVE co-property, with its prepared coating weather resistance, water resistance, solvent resistance and gloss can be comparable with solvent-based fluorocarbon paint.
In March 2008, at an anti-corrosion seminar organized by the American Association of Corrosion Engineers (NACE), Hydro Petroleum Energy of Norway tested and evaluated water-based coatings in accordance with NORSKOK M-501, which showed encouraging application prospects for the coating and repair of new facilities in ocean-going environments.
2.5 Environmentally friendly new materials environmentally friendly new materials are mainly low-toxic, non-toxic materials, such as composite phosphate rust-proof pigments instead of toxic, contaminated red Dan, chromate and other anti-rust pigments, strictly control the pigment in lead, cadmium, chromium, mercury, arsenic and other heavy metals content.
The Brocaven Laboratory of the U.S. Department of Energy has developed a bio-heavy anti-corrosion coating based on grain, crab and lobster shells that, at appropriate temperatures, becomes robust, smooth, and adheres tightly to aluminum or other metal surfaces to prevent corrosion of metals.
2.6 polycarp elastomer polycarp coating is a solvent-free, non-polluting high-performance heavy anti-corrosion coating, referred to as SPAA. SPUA is a two-part, 100% solid content, environmentally friendly, fast curing speed, not sensitive to humidity, temperature, and construction is not affected by environmental humidity; After curing coating film elasticity and strength, weather resistance, thermal stability is excellent, long-term outdoor use does not crack, does not fall off, good adhesion to steel, with excellent corrosion resistance. However, SPAA is extremely strict with the surface treatment requirements of the coated substrate, steel to be thoroughly blasted, after treatment must be immediately coated.
the United States and Taiwan have applied it to the corrosion prevention of offshore structures, especially the coating of offshore platform steel structures in the splash zone. Polycetamol mainly has aromatic polycetamol, adipose polycetamol and polytian gate holster adipose family polycetamol.
3 Marine anti-corrosion coating analysis and recommendations 3.1 coating application status and problems At present, most of the anti-corrosion coatings used in marine engineering for foreign multinational companies brand products, domestic paint products are rarely used. Whether in terms of paint product quality, or its quality control mechanism, domestic paint products and foreign products are very different. The main reason is that China's marine anti-corrosion coating development time is short, do not master the core technology, lack of research funds, the level of researchers is not high and other factors, these deficiencies greatly restrict the domestic paint into the international offshore market, but also weaken the competitiveness of domestic brands.
Based on the environment in which offshore products are used, it is necessary to take anti-corrosion protection measures, for offshore offshore marine products anti-corrosion coating, it is difficult to repair or re-coat at sea during the service period, extending the durability of anti-corrosion coating and anti-corrosion coating and offshore product service life synchronization is the ultimate goal of offshore anti-corrosion research. Therefore, the research and development of marine heavy anti-corrosion coatings and coating technology with a durability of more than 15 a in the marine environment, designed to reach 15 to 30 a durability in the marine environment metal coating and organic coating supporting system, multi-layer organic or inorganic coating supporting system, not only the national marine development strategy marine industry Anti-corrosion needs to be the focus of research, but also the national "12th Five-Year Plan" in the anti-corrosion coating technology research direction, and the development of cathode protection efficiency of primers, good shielding effect of medium paint and weather-resistant paint, as well as the appropriate coating supporting design is the technical key to the anti-corrosion coating supporting system.
Marine anti-corrosion coatings are currently mainly used to prevent corrosion of structures exposed to the ocean atmosphere, marine structures immersed in seawater, especially in deep water areas (such as ships and drilling platforms), submarine steel pipes, etc. also need to use coatings to prevent corrosion. Due to the low oxygen content in this area, the degree of corrosion is relatively low, currently mainly using epoxy coating, epoxy asphalt coating, epoxy glass scale coating, etc. , if you want to prevent the attachment of sea creatures, the use of epoxy coating and anti-fouling coating combination system. For the seabed area, because this area has the lowest degree of corrosion, the coating is mainly epoxy asphalt coating. In addition to liquid epoxy coatings, steel pipes also use a large number of molten epoxy powder coatings, which are often required to use more than 20 a under conditions of non-repair due to extremely difficult access.
anti-corrosion coatings used in seawater usually require good sea-resistant biological action and chemical stability to ensure that the coating can prevent deface and corrosion; Have good mechanical strength to ensure that the coating can withstand a certain amount of pressure and collision, to maintain the integrity of the coating so that it does not crack or fall off; There should be good adhesion to the surface and concrete of the steel pipe; The external plus cathode protection system has good compatibness and the coating is not peeled off when cathode protection is used.
anti-corrosion and coatings and electrochemical anti-corrosion are the main methods of marine anti-corrosion. The construction performance and repairability of coatings in seawater are more important than the corrosion resistance of coatings, so it is generally recommended that coating life be designed to be the same life or service-free as the subject of the coated structure. In addition, the use of anti-corrosion coatings that can be constructed in water is also the direction of current efforts to develop, foreign companies have developed such products, they are usually liquid high-solid content epoxy coatings.
Ship manufacturing is a marine engineering using marine anti-corrosion coating industry, with this closely related to China's ship anti-corrosion coating technology has also obtained rapid development, and reached a certain level, for example: coating process has been listed as one of the important content of ship design; Steel pre-treatment process in shipbuilding enterprises have been widely used, the establishment of a segmented rust removal, spraying workshop, and equipped with the corresponding automatic, semi-self