Anti-corrosion coatings for marine engineering

The 21st century is the century of the ocean, around the development of marine resources, marine environmental security and the protection of marine rights and interests, the international is carrying out a new round of marine competition. With China's efforts to promote the deep-sea strategy, increase the development process of the South China Sea and the construction of the Maritime Silk Road, China has put forward higher requirements for the development and maintenance of high-end marine equipment. Marine equipment and marine engineering have long been in service in the marine environment, and it is impossible to avoid the problems of corrosion damage, abrasive failure and biological defacement in complex and demanding
environment
. The corrosion of marine engineering materials causes nearly one trillion yuan of economic losses to the country every year, which has become one of the technical bottlenecks restricting the development of major marine engineering technology and equipment in China. 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 coating protection technology of marine engineering structural facilities, which can not only effectively delay the occurrence of corrosion and reduce the cost of maintenance and repair, but also reduce the occurrence of malignant accidents and improve the service safety of offshore facilities.
application prospective
China's marine-related coatings accounted for about 1/10 of the total paint market, market demand of more than 35 billion yuan. With the development of China's marine industry, the average annual growth rate of marine coatings demand will exceed 20%. The development of marine heavy anti-corrosion coating is to serve the overall strategy of the development of the national marine industry, and it is also an essential part of China's development from offshore to deep sea, and become a major maritime country. By using the super shielding effect, conductive performance and chemical stability of graphene two-dimensional nano-sheets, the permeability, electrostectronicity and wear resistance of coatings can be greatly improved. Graphene added heavy anti-corrosion coatings are expected to be used on a large scale in the fields of ships, offshore oil rigs, wind power generation, coastal reef facilities and other fields.
latest research progress
Marine anti-corrosion coatings can be divided into marine steel structure anti-corrosion coatings and non-steel structures (mainly marine concrete) anti-corrosion coatings. Marine anti-corrosion coating system mainly has 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. In the marine environment, the essence of material corrosion damage is electrochemical corrosion, the mechanism of which is electrochemical corrosion and chloride ion corrosion caused by water, oxygen and chloride ion corrosion factors penetrating the surface of the material under the coupling of multiple marine environmental factors. Usually inorganic fillers such as SiO2, TiO2, ZnO, BaSO4 and other inorganic nanofillers in organic coatings can form a good synergy with organic polymer resins, fill the gaps in the coating, enhance the tightness of the coating and anti-ion permeability, and can improve the fluidity of the coating, increase the adhesion, hardness, finish and heat resistance of the coating, is an important development direction of the marine heavy coating. In addition, the addition of scale fillers to the heavy anti-corrosion coating system also has a good effect of blocking the penetration of corrosion media. Commonly used scale fillers are mainly flaky mica, mica iron oxide, graphite, flaky zinc powder, stainless steel and glass scales. Among them, flaky mica, mica iron oxide, graphite and so on because of the cheap, in the ship rust-proof coating has been a lot of applications, however, the thicker inorganical sheet filler (2 to 5 m) requires the thickness of the coating is much larger than the conventional coating protection system, the coating process is complex.
Since 2004, when physicists Andree Geim and Konstantin Novosholov at the University of Manchester successfully removed single-layer graphene from graphite, graphene has attracted the attention of academia and industry for its unique and excellent conductivity, chemical and thermal stability, thermal conductivity, lubricity and electrical properties. In particular, a single layer of graphene thickness of only one carbon atom diameter size (0.335 nm), its stable SP2 hybrid structure enables it to form a physical barrier between the metal and the corrosion medium, to prevent the spread and penetration of the corrosion medium, is considered to be the thinnest known corrosion protection coating. Adding graphene two-dimensional nano-sheets to anti-corrosion coatings can combine the performance of graphene and organic coatings, which is the most likely way to achieve graphene coating applications in the field of anti-corrosion. Graphene's ultra-thin two-dimensional nano-sheet layer structure can prevent the diffusion of corrosive media in the coating by acting as a "maze-like" physical barrier, significantly reducing the corrosion rate of the metal and improving the corrosion resistance of the metal. At the same time, the small size effect of graphene can be filled into the pores and defects of the coating system, reducing the cracks in the coating and increasing the tightness of the coating. Graphene's excellent chemical stability can improve the coating's heat resistance, acid and alkaline resistance, while graphene's high conductivity and lubricity can give the coating new properties of conductive static electricity, self-lubrication and wear resistance. In addition, from an electrochemical point of view, graphene's high conductivity can quickly transfer corrosion current, prevent electrochemical reactions on the metal surface, act as passivation on the metal substrate, and thus improve the corrosion resistance of the coating. Of course, there are studies that suggest that the high conductivity of graphene accelerates the electrochemical corrosion of graphene.