This article introduces the anti-corrosion mechanism of marine anti-corrosion coatings; reviews the latest research progress of marine anti-corrosion coatings at home and abroad.
The properties and applications of epoxy anticorrosive coatings, polyurethane anticorrosive coatings, rubber anticorrosive coatings, fluororesin anticorrosive coatings, silicone resin coatings, polyurea elastomer anticorrosive coatings and zinc-rich coatings are discussed, and the above-mentioned various The lack of coatings and the direction of future research.
In addition, this article also looks forward to the application prospects and development trends of marine anti-corrosion coatings.
The ocean occupies about 70% of the earth’s surface area. In world trade, more than 90% of freight is transported by the ocean. Marine resources and the shipping industry have become indispensable pillars in the development of the world economy. However, with the reciprocating impact of sea wind and waves on metal components; the corrosion of metal materials by sea water, marine organisms and their metabolites, etc., the marine environment has become an extremely harsh corrosive environment. Submarines and ships, whether in or on the sea, need to be made of high-strength, corrosion-resistant materials and painted with anti-corrosion coatings for protection. Therefore, the search for the most suitable marine anticorrosive coating has attracted widespread attention.
During the "Twelfth Five-Year Plan" period, China is at a critical stage of transition to an intensive low-carbon economy, and it is also a critical period for the implementation of the maritime strategy. The rapid development of ocean transportation, deep-sea new energy development, coastal ports, ships and other industries is preventing marine corrosion. Coatings have higher requirements, and it is objectively necessary to develop green, harmless, long-life and economical marine anti-corrosion coatings. With the rapid growth in the demand for marine anti-corrosion coatings in various industries, the marine anti-corrosion coating industry will surely get an unprecedented golden development period, and the types, performance, application scope, and scale of products will develop by leaps and bounds. This article introduces the development status of marine anti-corrosion coatings, focusing on several types of marine anti-corrosion coatings with significant anti-corrosion properties.
Overview of anti-corrosion coatings
The protection of marine metal substrates is mainly through the use of corrosion-resistant materials, the addition of corrosion inhibitors, metal surface modification, coating protection and electrochemical protection. Among them, coating protection is a traditional marine anti-corrosion technology: the use of corrosion-resistant paint is applied to the surface of the metal substrate and cured into a film at high or normal temperature to protect it. The anti-corrosion mechanism of anti-corrosion coating includes: shielding effect, passivation effect, protective effect of anti-rust filler, cathodic protection and so on. Coating protection has the advantages of simple construction, obvious anti-corrosion effect and high economic benefits, and has been widely used in the field of marine anti-corrosion.
The performance of the coating determines the protective effect of the coating. The protective coating used in the field of marine heavy-duty anti-corrosion should have the following advantages: good mechanical properties, resistance to rain, sea water erosion and collision and even friction; good stability, resistance to acids, alkalis, salts, and chemicals , Oil resistance, aging resistance and UV resistance; strong adhesion, strong adhesion and bonding with the substrate; easy construction, green and environmental protection. In addition, there are also certain requirements for the shielding, hydrophobicity, stain resistance and service life of the coating.
The properties of coatings are not independent, they influence each other and are closely related. The development of anti-corrosion coatings with the above advantages at the same time is one of the most important tasks at present.
Types of marine anticorrosive coatings
There are various types of steel structure corrosion in marine engineering: galvanic corrosion, cavitation corrosion, abrasion corrosion and impact corrosion, hydrogen evolution corrosion, oxygen absorption corrosion, etc. The most widely used heavy-duty anti-corrosion coatings mainly include: epoxy anti-corrosion coatings, fluorocarbon anti-corrosion coatings, polyurethane anti-corrosion coatings, rubber anti-corrosion coatings, silicone resin coatings, polyurea elastomer anti-corrosion coatings, glass flake anti-corrosion coatings and Organic zinc-rich paint.
The following is a brief introduction to the most widely used anti-corrosion coatings:
epoxy anticorrosive coating
Epoxy anticorrosive coatings are mainly composed of epoxy resin, mixed with pigments, driers, additives, etc. Epoxy resin coatings have excellent performance: high adhesion, high strength, chemical resistance and abrasion resistance. It is currently one of the earliest and most widely used types of heavy-duty coatings in the field of marine heavy-duty corrosion.
There are many types of epoxy anticorrosive coatings, which are mainly divided into two categories: bisphenol A epoxy resin and novolac epoxy resin. The molecular structure of bisphenol A epoxy resin contains hydroxyl groups, ether bonds and epoxy groups, which has strong adhesion to the substrate; the benzene ring makes the resin have strong mechanical strength and wear resistance; after coating, it is acid and alkali resistant, Excellent corrosion resistance and chemical resistance; curing at room temperature, convenient construction, low curing shrinkage, no volatile substances, and environmental protection.
Phenolic epoxy resin, because it contains more epoxy groups, has stronger corrosion resistance and adhesion; it has greater curing crosslinking degree, stronger compactness, and has the high temperature resistance and corrosion resistance of phenolic resin. However, the increase of epoxy groups increases the brittleness and affects its application range. Synthesize bisphenol A novolac epoxy resin with bisphenol A instead of phenol. The free phenol content is low, and the molecular weight distribution is narrow. The introduction of bisphenol A makes the resin stronger, the shrinkage rate is lower, and the increase of epoxy groups makes adhesion Strong force, flexibility, thermal stability, insulation, water resistance and corrosion resistance are more excellent.
Modified epoxy resin through fillers and other means can expand its application range. Ghaffari et al. used bifunctional silanes as modifiers and used infrared spectroscopy and thermogravimetric analysis to study the properties of suspended nano-fillers and coatings in epoxy composites. The research showed that the modifiers can disperse suspended nano-fillers. Even better, after adding 0.5% mass fraction of modified suspended nano-filler, the coating effect is obvious during the immersion period.
Paula et al. analyzed the microstructure of water-based epoxy resin, and the results showed that the average pinhole size of the coating surface has a good correlation with chloride permeability.
Liu Jiangtao and others analyzed the ratio of water-based modified amine epoxy curing agent and liquid epoxy resin, and the selection of fillers and additives. The results showed that the hydrogen equivalent ratio of epoxy group amine is 1:1, pigment, non-ionic and ion. When used together with wetting agent, the finished paint film has excellent mechanical properties and chemical resistance.
Mukesh et al. used cardanol instead of bisphenol A to synthesize a new type of epoxy resin and performed infrared spectroscopy and nuclear magnetic resonance spectroscopy. The results showed that: the new type of epoxy resin cardanol only needs 40% of the amount of bisphenol A in the original epoxy resin~ 60% can achieve the same performance.
But at present, these modification methods can only improve a certain characteristic of the resin, and the application advantage is not obvious when facing the complex marine corrosion environment. According to different application fields, it is its development direction to develop water-based or high-solid epoxy anticorrosive coatings by mixing with various resins and fillers, and combining physical and chemical modification methods. For example, we use bisphenol AF instead of double Phenolic resin is synthesized from phenol A, and then epoxidized to obtain fluorine-containing epoxy resin, which not only has excellent adsorption performance to the substrate, but also greatly improves the anti-corrosion performance of epoxy resin, which has outstanding advantages in the field of marine anti-corrosion . The performance of the coating depends on the characteristics of the resin. It also includes the research and development of modifiers and the optimization of the coating process. It is also the research direction of epoxy anticorrosive coatings in the future.
Fluorocarbon anticorrosive coating
Fluorocarbon anticorrosive coatings use fluorine-containing resin as the main film-forming material. The fluorine atom has large electronegativity, small radius, short CF bond bond length, strong bond energy, and low polarization rate. This type of coating exhibits super weather resistance and resistance. Thermal and chemical resistance, with excellent self-cleaning performance, anti-fouling performance and super corrosion resistance.
In 1965, the American pennwalt company introduced PVDF as an architectural coating as a sign, and fluorocarbon resins began to be applied in the field of anti-corrosion. In 1982, Asahi Glass Company developed FEVE, which realized room temperature curing, which greatly expanded the application fields of fluorocarbon coatings. Fluorocarbon coatings are used in fluorocarbon coatings from difluorinated to trifluorinated and tetrafluorinated, from high temperature curing to normal temperature curing, and then water-based fluorocarbon emulsion resins are used in fluorocarbon coatings, gradually forming diverse and widely used fluorocarbon coatings System and application areas have been greatly expanded.
In recent years, fluorocarbon coatings have been modified in different ways or mixed with various coatings to optimize the performance of fluorocoatings and expand their application fields. Lu et al. doped fluorocarbon coatings with different amounts of anatase TiO2 nanoparticles to test the coating performance. The results showed that the TiO2 nanoparticles added to the fluorocarbon coatings produced coatings with better heat resistance, weather resistance and Excellent self-cleaning performance. Kim et al. sprayed water-soluble fluorocarbon sealing materials by low-temperature spray coating, which showed high corrosion current density and corrosion resistance. LL'darkhanova and others used carbon nanotubes and carbon nanofibers to modify the fluorocarbon resin. The nanostructure formed on the surface of the coating and the inherent hydrophobicity of the fluorocarbon resin have a synergistic effect, which greatly improves the hydrophobicity of the coating.
These modifications only enhance or improve a certain performance of the coating. It is impossible to completely apply all the modification methods to a coating. Therefore, to change this situation, it is necessary to structurally design and synthesize new fluororesin. It is the focus of the research and development of fluorocarbon resin to make the resin body have comprehensive excellent performance, and then improve some of its performance defects through modification methods. In addition, the main factors affecting the promotion of fluorocarbon coatings are the high cost of coatings, the need for high-temperature baking of coatings, poor hardness, and easy to miss coating. In short, the use of new monomers for copolymerization, the introduction of fluorine elements in different types of resins, and multi-component polymerization are the main ways to prepare new fluorocarbon coatings and future research directions.
Rubber anticorrosive coating
Rubber coatings use natural rubber derivatives or synthetic rubber as the main film-forming material. There are mainly chlorosulfonated polyethylene anticorrosive coatings and chlorinated rubber anticorrosive coatings. The rubber coating is non-toxic, odorless, non-irritating to the skin, the coating film has strong corrosion resistance, strong adhesion to the substrate, and has the advantages of fast drying, water resistance and wear resistance, and anti-aging. The rubber anticorrosive coating is mainly used for ships, sluices, Chemical and other fields. Chlorosulfonated polyethylene anticorrosive coatings use chlorosulfonated polyethylene rubber as the main film-forming material, which is non-lipophilic, non-hydrophilic, and has excellent flame retardancy, weather resistance, heat resistance and low temperature resistance. The disadvantages are: the adhesion to the substrate is not high, it needs to be mixed with other resins or modified to improve the adhesion; the solubility is low, the amount of solvent required is large, causing pollution and waste.
Chlorinated rubber anticorrosive paint is made by using carbon tetrachloride as the solvent, refining natural rubber and introducing chlorine gas. There are no active chemical groups, and it has excellent chemical resistance, water resistance, fog resistance and weather resistance. Mixed with other coatings, it has stronger corrosion resistance and longer service life; when used alone, the adhesion to the substrate is not high, and the aging resistance and UV resistance are not strong.
In recent years, some researchers have improved the defects of traditional rubber anticorrosive coatings through modification or mixing with other coatings. Hwang et al. used rubber and epoxy resin to modify the amine-terminated rubber with different amounts of flaky graphene microchips. The test results showed that the impact strength and toughness of the modified composite coating were greatly improved. Bulgakov et al. modified chlorosulfonated polyethylene rubber with amino compounds to increase the bonding strength by 2 to 5 times. Li Shi et al. used medium and long oil alkyd resins, epoxy resins, etc. to modify chlorinated rubber, and painted them on offshore platforms, ships and other equipment. The measurement results showed that the adhesion and aging resistance of the coating were greatly improved. Enhanced.
However, although these modification methods have improved the performance of the coating, they still use carbon tetrachloride as a solvent, which is toxic and destroys the ozone layer, which limits its application. The development of low-VOC chlorinated rubber coatings is Future development direction. For example, the use of water-phase method to synthesize chlorinated rubber and the development of water-based chlorinated rubber coatings have provided us with solutions. However, the stability or actual effect of product quality cannot meet the technical requirements of the harsh ocean environment. New solvents are developed to replace tetrachloride. The production of chlorinated rubber by chemical carbon is still a hot spot and difficulty in the research and development of the rubber coating industry.
Silicone resin paint
Silicone resin coating is an elemental organic coating with silicone resin or modified silicone resin as the main film-forming substance. The main components are pure silicone resin coating and modified silicone resin coating. It has strong heat and cold resistance and insulation Excellent performance in terms of resistance, adhesion, flexibility, and mildew resistance. Modified silicone resins are more widely used, including mechanical mixing type and polycondensation type. The silicone resin can be modified by adding different fillers or pigments to enhance its heat resistance, insulation and weather resistance.
Researchers at home and abroad have adopted different ways to modify silicone resin coatings and have achieved remarkable results. Lee et al. used the self-healing agent dimethyl siloxane and dimethyl hydrogen siloxane double emulsion to electrostatically introduce the core-shell nanofiber coating core. The results showed that this protective coating has high transparency, self-healing ability and resistance. Strong corrosion performance.
Balgude et al. modified silane, studied its corrosion protection to carbon steel, and performed characterization and structural analysis of 4 coatings with different silane content. The results showed that 20% of the silane-modified coating was in the metal coating compared to other formulations. The interface forms more metal-oxygen-silicon covalent bonds, and its overall performance is stronger.
Although silicone resin coating has outstanding advantages such as excellent high and low temperature resistance, weather resistance, chemical resistance, abrasion resistance, etc., its shortcomings such as low strength and low adhesion to the substrate also limit its application range. Future work is mainly to adopt different methods to modify, such as inorganic-organic hybrid technology, so that it has the best characteristics of organic and inorganic materials; through probing the film forming mechanism of silicone resin coatings, various polymers such as acrylic acid Resin, epoxy resin, etc. are modified to obtain more excellent silicone modified coatings; cross-linked silicone resin coatings are prepared to enhance their compactness, improve water resistance, solvent resistance and heat resistance; make silicone The development of resin coatings in the direction of low pollution, health and environmental protection is also the focus of future research and development.
polyurethane anticorrosive coating
Polyurethane coatings are a common type of coatings, which have similar properties to epoxy coatings and are divided into two-component and one-component polyurethane coatings. In addition to the presence of urethane bonds in polyurethane, there are many -OH, -NCO and unsaturated double bonds. The coating has excellent acid and alkali resistance, oil resistance, corrosion resistance, high and low temperature resistance and abrasion resistance. Polyurethane coatings are high-solids and low-VOC coatings with very low emissions of environmental pollutants; polyurethane coatings have strong adhesion to the substrate, excellent physical and mechanical properties, and strong decorative properties. They can be used as topcoats in the field of heavy corrosion protection.
At present, there are many ways to modify waterborne polyurethane anticorrosive coatings at home and abroad, mainly including: epoxy resin modification, silicone copolymer modification, nano modification, and composite modification. The performance of the modified waterborne polyurethane anticorrosive coating has been greatly improved, but there are still problems such as weak water resistance, harsh construction conditions, and high product prices.
The research and development of new waterborne polyurethane anticorrosive coating modification methods is the main direction of the scientific research of waterborne polyurethane anticorrosive coatings. For example, the use of emulsifiers or the introduction of carboxyl, hydroxyl and other hydrophilic groups on the main chain to prepare waterborne polyurethane coatings is focused on how to improve Water resistance and shortening of curing time; in addition, the research and development of two-component polyurethane coatings is very immature, which is also a research focus in the future. In short, the development of high-performance water-based, high-solid content polyurethane coatings, combined with different types of coatings such as epoxy resins and fluorocarbon resins, is the future direction of research and development.
Polyurea elastomer anticorrosive coating
Polyurea elastomer coatings are formed by the reaction of amino compounds and isocyanates, and are mostly used for corrosion protection of marine bridges. It was successfully developed by the United States in the late 1980s. Because of its excellent performance, it has been widely used worldwide. It is a new, efficient and easy-to-paint after high-solid, powder coating, water-based coating, light-curing coating, etc. Two-component pure polyurea elastomer coating. This kind of high-thick film elastomer coating has obvious characteristics: high solid content, green and environmental protection, thick and dense and flexible coating film, strong adhesion to the substrate, excellent UV resistance and impact resistance, and easy construction.
There are many researches on polyurea elastomer coatings at home and abroad.
Feng et al. studied the addition of different amounts of polyurea elastomer to polyurea block polyamide copolymer coatings, and the results showed that when the mole fraction of polyurea content reaches 50%, the self-assembly effect induced by hydrogen bonding increases. The crystallinity of the coating is enhanced, the corrosion resistance of the coating is enhanced, and the surface energy is reduced.
Huang et al. used Qtech-412 pure polyurea heavy-duty anti-corrosion coating for coating, exposed to aging in an artificial ocean atmosphere, and tested performance with infrared spectroscopy and DSC. The coating has good mechanical properties, good UV resistance, stable structure, and Excellent corrosion performance.
However, these modification methods have not touched the main reasons that restrict the application of polyurea elastomer coatings, or have little improvement, because the main defects of polyurea elastomer coatings are: too fast curing speed, poor interlayer adhesion, and high temperature resistance And corrosion resistance is not as good as fluorocarbon coatings, etc. The focus of the research should be to conduct detailed research on its various properties. By comparing the effects of the use of different chain extenders, fillers, and coupling agents on the coating properties, the overall performance can be developed. Excellent polyurea elastomer coating. In addition, the spraying of polyurea elastomer coatings is a very advanced technology, and the quality and technology of the construction personnel are also the reasons for its performance; secondly, the main raw materials and spraying equipment need to be imported, which leads to high costs and restricts China's polyurea elastomer coatings. An important reason for development. In the future, researching and developing moderately priced polyurea elastomer coatings and establishing standardized spraying standards are the most difficult points in the research of polyurea elastomer coatings.
glass flake heavy anti-corrosion coating
Glass flake anticorrosive coating is a type of coating made by adding resin as the main film-forming material, adding special glass flakes as aggregate, and adding suitable additives. The characteristics are: the glass flakes are thin, overlap with the coating, inhibit the penetration of the medium, and have an excellent shielding effect; the coating film has strong adhesion and mechanical properties, corrosion resistance and toughness; the flakes make the coating and the substrate The stress is reduced to prevent cracks and shedding of the coating film; the scale reflects a large amount of ultraviolet rays in the coating, and the resin has excellent ultraviolet resistance, weather resistance and aging resistance.
There are mainly the following widely used: epoxy glass flake heavy anticorrosive paint, polyurethane glass flake heavy anticorrosive paint, epoxy coal tar pitch glass flake heavy anticorrosive paint, high chlorinated polyethylene glass flake heavy anticorrosive paint. Different types of coatings have different excellent properties. Among them, the comprehensive performance of epoxy glass flake heavy-duty anti-corrosion coating is the most prominent, and it is the most widely used in the field of marine anti-corrosion. It uses epoxy resin as the main film-forming substance, which is comparable to ordinary epoxy anti-corrosion coatings. Compared with, its anti-medium permeability, wear resistance and corrosion resistance are stronger, the coating has better adhesion, corrosion resistance, chemical resistance, anti-corrosion life and other properties. The construction conditions are simple and fast curing. It is suitable for topcoat or Intermediate paint is used in coating systems.
But the current modification methods rarely touch the effect of the difference of scales on the coating performance. How to improve the chemical resistance of the glass flake itself, choose the appropriate thickness of the flake, and use the relevant additives to treat the flakes differently before use is an important method to improve the performance of the glass flake coating, and it is the main direction of future research. In addition, trying to use glass flakes as aggregates, different types of resins as film-forming substances, and preparing different glass flake heavy-duty anticorrosive coatings are also important contents of research.
Zinc-rich coating is an epoxy powder coating with zinc powder as filler, mainly including organic and inorganic zinc-rich coatings, which are widely used on marine bridges, large steel structures, ships and other equipment. The anti-corrosion mechanism of zinc-rich coatings includes: shielding effect, electrochemical protection, self-repairing effect of coating film, and passivation effect.
Organic zinc-rich coatings mostly use epoxy resin and polyurethane resin as film-forming materials; inorganic zinc-rich coatings use water-based silicate resin, ethyl silicate, etc. as film-forming materials. Organic zinc-rich paint has good construction performance, low substrate and strong surface treatment, but its heat resistance, conductivity, solvent resistance and other properties are inferior to inorganic type. Organic type is miscible with most coatings. There is a synergistic effect.
Many scientific researchers have conducted research on zinc-rich coatings. Yang et al. used scanning electron microscopy and energy dispersive spectroscopy to dynamically observe and analyze the coating, and evaluated the anti-corrosion effect of the anti-corrosion system composed of layered coatings, and proved the excellent anti-corrosion performance of zinc-rich coatings. Pandey et al. and Gergely et al. modified the zinc-rich coatings with different nanoparticles, and analyzed by various means, which facilitated the development of new zinc-rich coatings.
These modification methods have improved the performance of coatings to a certain extent. At present, many researchers have combined different types of resins with zinc-rich coatings to analyze their performance differences. If these two methods can be combined, first use different methods to modify the zinc-rich coating, and then combine it with different types of coatings, such as the preparation of modified zinc-rich coatings containing epoxy resin, which will also have epoxy resin adhesion The advantages of Ligao have overcome the shortcomings of poor film-forming properties of inorganic zinc-rich coatings and high surface treatment requirements, and a protective coating with excellent performance will be developed. By comparing the combined effects of different types of resins and modified zinc-rich coatings, we have screened out the most excellent types of coatings, which will greatly broaden the scope of application of zinc-rich coatings and improve their anti-corrosion effects. This will be the future study of zinc-rich coatings. Important direction.
In the field of marine heavy anti-corrosion, in addition to the wide application of the above types of coatings, chlorine-containing resin heavy-duty anti-corrosion coatings, polyphenylene sulfide anti-corrosion coatings, polyaniline anti-corrosion coatings, phenolic resin coatings, acrylic anti-corrosion coatings, etc., due to their different The properties and performance are also used in different fields.
With the rapid development of the marine economy, people pay more and more attention to marine anti-corrosion, and the development and application of marine anti-corrosion coatings has received strong attention at home and abroad. The design and development of marine anticorrosive coatings has high technical content, large capital investment and long research and development cycles. Starting from the corrosion characteristics of the marine environment, and taking one or more corrosion mechanisms as the starting point, different anti-corrosion coatings or coating systems with synergistic effects must be developed to adapt to different corrosive environments.
Traditional anti-corrosion coatings are limited in application due to the large solvent pollution, short anti-corrosion life, corrosion resistance, and weak weather resistance. With the increasing awareness of environmental protection, the development of more energy-efficient and green new marine anti-corrosion coatings has also become the demand of the times. There are many types of existing coatings. Epoxy resin coatings, fluorocarbon resin coatings, polyurethane coatings, zinc-rich coatings, etc. have been widely used in many fields, and the modification methods are also diverse. In general, the existing research The method is rarely fundamental, that is, from the structure to improve the performance of the resin, which leads to the performance of the modified coating loses the other, and it is difficult to have excellent comprehensive properties.
In view of the current shortcomings, we chose fluorocarbon resin as a breakthrough. Its unique performance advantages have been paid attention to in the field of marine anti-corrosion. How to develop new types of fluorocarbon resins is the focus of fluorocarbon coatings. We have developed a fluorocarbon coating prepared with bisphenol AF novolac epoxy resin as the main body and adding different additives and additives. Because the polymer backbone contains a diphenol-based propane structure, it has strong mechanical strength and Abrasion resistance, the curing shrinkage rate of the coating is lower, and the toughness is much higher than that of ordinary phenolic epoxy resin; it contains a large amount of epoxy groups, which forms a strong adhesion with the substrate; especially the introduction of fluorine This fluorocarbon resin is water and oil repellent, has particularly excellent corrosion resistance, UV resistance and chemical resistance, and the coating is flexible and smooth, and has self-cleaning properties. This coating combines the common advantages of phenolic resin coatings, epoxy resin coatings and fluorocarbon resin coatings. If its function is optimized by suitable modification methods, and it is prepared into water-based fluorocarbon coatings, it will definitely make it in The field of marine anticorrosion has been greatly applied.
In the future, the research and development of marine anticorrosive coatings will mainly develop in the direction of green environmental protection, long life, thick film, low surface treatment, and easy construction. High-solid, low-VOC, solvent-free powder coatings and room temperature curing coatings are the development focus; water-soluble coatings are the research direction of environmentally friendly anti-corrosion coatings; the application of different coatings to modify nanoparticles to improve their coating performance has great research prospects; The research on the mixed use of inorganic-organic coatings also provides us with a scientific research idea. In short, the development of different types of anti-corrosion coatings and the rational use of multiple modification methods based on the corrosion characteristics of different fields are the fundamental research ideas for effectively curbing marine anti-corrosion in the future. With the comprehensive advancement of my country's "13th Five-Year Plan", marine anti-corrosion coatings will surely get more extensive and rapid development, escorting my country's strategy of entering the ocean.