Recently, Dr. Wang Fangfang from the School of Materials Engineering, Shaanxi Polytechnic has made new progress in the research of ultra-high anticorrosive waterborne coatings.

Ultra-high anticorrosive water-based coating is a challenge and great demand of sustainable development of environmental protection in China. The water-filled conductive composite coating is an indispensable key material for surface corrosion prevention of metal equipment in the field of petrochemical industry. At present, it is faced with the problems of large amount of conductive particles added and easy agglomeration, and the conductivity and corrosion resistance of the coating cannot be taken into account.

To solve above problems, Dr Fang-fang wang in ultra high anticorrosion coating, the low content of modified multi-walled carbon nanotubes (MWCNTs) and polytetrafluoroethylene (PTFE) emulsion particles are added to the WPU coatings, using self-made liquid electrostatic spraying device, using PTFE low surface energy and rough micro structure of MWCNTs structure produce synergistic effect, A superhydrophobic conducting WPU coating was prepared.

With the help of coupling agent, WPU, PTFE and MWCNTs were bonded into a whole, which improved the coating uniformity, reduced the curing interface of WPU and PTFE, and enhanced the corrosion resistance of the coating. Because the silane coupling agent can dehydrate with the polar Fe surface to form -NH2 covalent bond, the bonding force between the coating and the substrate is improved, and the problems of low adhesion, easy delamination and easy wear of the coating are solved. This study provides an important basis for electrostatic spraying to prepare water-based conductive coatings with high adhesion and self-cleaning function.

The market situation

China's anticorrosive coating industry started late compared with the world's leading countries, but has also made great progress in recent years, the world's famous anticorrosive coating companies have set up their own factories and laboratories in China. In 2020, China's anti-corrosion coating production about 6.61 million tons, year-on-year growth of 3.9%, in recent years the growth of basic tends to be stable.

Oil and gas market demand for heavy corrosion coatings. Anticorrosive coating is mainly used in Marine engineering, transportation, energy, industry and other national pillar industries. According to new materials online data, in the high performance heavy corrosion coatings market, the oil and gas industry market demand is large, accounting for the highest 24% in 2020; Followed by the Marine market and petrochemical market accounted for 20% and 14% respectively.

Foreign companies account for 80 per cent of the high-end market. At present, international giants are still ahead of domestic enterprises in the degree of perfection of anti-corrosion coatings industry chain and technological leadership, especially in high-end fields such as container and ship coatings. Domestic anti-corrosion coatings still need to break through barriers such as high-performance formula and supporting construction technology. In addition, the domestic anti-corrosion coating enterprises that survive in the low-end market are mainly small and medium-sized enterprises, and there are many problems, such as product homogenization competition.





Graphene provides an opportunity for the development of anticorrosive coatings

Graphene is a new two-dimensional material composed of carbon atoms in a single sheet structure, which is a hexagonal honeycomb lattice planar film composed of carbon atoms in sp2 hybrid orbitals. Graphene has long been considered a hypothetical structure that cannot be stabilized on its own. It wasn't until 2004 that physicists Andre Geim and Konstantin Novoselov at the University of Manchester in the UK managed to isolate graphene from graphite in the lab, proving that it could exist on its own. It is without a doubt the strongest material in the world. If you were to cover a cup with graphene the thickness of food wrap, it would take as much force as an elephant standing on a pencil to Pierce it.

The discovery of graphene has provided an opportunity for the development of anticorrosive coatings. Researchers have added graphene or GO to anticorrosive coatings using epoxy resins as film forming materials to obtain better corrosion resistance coatings. Pure graphene coatings and graphene composite coatings can be prepared by adding graphene to coatings. Pure graphene coating is a functional coating that pure graphene plays a role in corrosion prevention and electrical conductivity on metal surface. Graphene composite coating is the first composite of graphene and polymer resin, and then the composite material to prepare functional coatings, graphene can significantly improve the performance of polymer, so graphene composite coating has become an important application of graphene research field.

The conjugated structure of graphene gives it high electron mobility and excellent electrical properties, which are the most desirable properties to exploit. Compared with traditional conductive materials, such as silver powder, copper powder and zinc oxide, graphene not only has good conductive properties, but also has excellent mechanical properties and thermal conductivity. It is an excellent additive for conductive coatings.

The two-dimensional lamellar structure of graphene makes it superimposed in the coating layer by layer, thus forming a dense physical isolation layer, thus improving the flame retardant performance; Graphene can also be cross-linked with resins to further form a dense protective film in the paint, which acts as a barrier to air, thus acting as a flame retardant.

The high surface area of graphene makes its surface adsorption strong, which can form a network structure when the coating dries, so as to enhance the adsorption between the coating and the substrate, make the coating more compact, and improve the adhesion of the coating to the substrate.

In December 2020, a new version of the Green Paper on Technology Innovation in Key Areas of China's Manufacturing Industry -- Technology Roadmap (2019), compiled and revised by the Chinese Academy of Engineering and the National Strategic Advisory Committee for Building a strong Manufacturing Country, was released, proposing to promote the large-scale application of graphene in anti-corrosion coatings and other fields, as well as achieve breakthroughs and technological applications of core technologies. At the 22nd China Hi-tech Fair in 2020, graphene composite ceramic anticorrosive coating was awarded as the excellent innovative product of the Fair due to its heavy anticorrosive and high anticorrosive technology and market innovation. Graphene has shown excellent performance in the field of anticorrosive coatings, and graphene modified anticorrosive coatings have been included in the 13th Five-Year Plan and the list of new materials for key development of the Ministry of Industry and Information Technology. As early as 2016, there has been a surge of research in the literature related to graphene coatings. Related literature research disciplines of graphene coatings, with materials science and chemistry as the core, mainly extend to nanoscience and technology, engineering, electrochemistry, optics, energy and fuel science and other disciplines. From the perspective of its development trend, the research of graphene coatings has gradually penetrated into the application field from the basic research at the micro level.

Policies to promote the industry to high performance, green environmental protection direction upgrade

On the development of anticorrosive coatings, in recent years, the national level has introduced a series of policies to regulate the industry toward the direction of environmental protection and energy saving transformation. Overall, the national policy is promoting the industry to high performance, green environmental protection direction upgrade. Upstream supply situation is good, anticorrosive coating raw materials of various types, the overall supply is sufficient. The application of industrial protection in downstream development accounted for as much as 46%.

ZhongGuo anticorrosive coating industry started late compared with the world's leading countries, but it has also made great progress in recent years. The supply of domestic production is increasing steadily, which is about to exceed 5 million tons. In terms of demand, the sales revenue of enterprises in the domestic market has exceeded 100 billion yuan, and the price of products of leading enterprises in the industry is declining.

The industrial competition pattern is mainly divided into regional competition, enterprise competition, production enterprises concentrated in the eastern and southern coastal areas, Guangdong Province enterprises most. The domestic market is mainly occupied by foreign capital, and the competitiveness of domestic brands is weak.

YuCe shows that the industry will develop in the direction of environmental protection, functionality and integration of coating and painting. It is expected that the market scale of QuanGuo anticorrosive coatings will exceed 140 billion yuan by 2026.

Article sources: Admission Office of Shaanxi Institute of Technology, Qianzhan Industry Research Institute, China Building Materials News, Changling Anti-corrosion materials