It causes about 700 billion in losses every year! We want to reduce this number

Produced by: Science Popularization China

Author: Zhao Wenjie and Cao Jintao (Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)

Producer: China Science Expo

Editor's note: In order to unveil the mystery of scientific work, the China Science Popularization Frontier Science Project launched a series of articles called "Me and My Research", inviting scientists to write articles themselves, share their scientific research experiences, and create a scientific world. Let us follow the explorers at the forefront of science and technology and embark on a journey full of passion, challenges, and surprises.

I believe you and I must have the same feeling. Whenever I drive on the cross-sea bridge, I can't help but marvel at its grandeur. It lies like a giant steel dragon on the turbulent sea.

Hong Kong-Zhuhai-Macao Bridge

(Photo source: Xinhua News Agency reporter Chen Yehua took this photo on September 11, 2020)

However, in this vast sea area, our marine engineering equipment is silently suffering from an invisible threat - marine corrosion.

This is an ordinary metal pillar on the beach. It didn't take long for the sea water to corrode it into this rusty appearance.

(Photo source: Veer Gallery)

In fact, the problem of metal corrosion is prevalent in many areas of the national economy. According to statistics, the economic losses caused by corrosion in my country are as high as 2 trillion yuan each year, of which marine corrosion losses account for about one-third of the total corrosion losses, or about 700 billion yuan.

How can we reduce these losses? First, we need to understand how marine corrosion occurs.

Marine corrosion is a slow and ongoing process.

According to different marine environments, it can be divided into the atmospheric zone, the splash zone, the tidal zone, the full immersion zone and the sea mud zone. Among them, the corrosion in the splash zone is the most serious . In this area, marine engineering equipment must not only withstand electrochemical corrosion from salt, oxygen and water, but also face mechanical damage from waves.

This is like continuously hitting a scabby wound; seawater can easily destroy marine engineering equipment.

Take steel pipe piles as an example. As the most important infrastructure in marine engineering, they support major facilities such as cross-sea bridges and offshore wind power. However, steel pipe piles face severe corrosion challenges in the splash zone during their service in the ocean. What we can see is that they have to withstand the challenges of complex and harsh working conditions such as early tide, late tide, splash, and alternating dry and wet environments.

What we can’t see? It has to withstand multiple tests such as salt, oxygen, ultraviolet erosion, waves, and silt erosion. These damage factors are strongly coupled together, forming a world-class anti-corrosion problem.

Since people realized the power of marine corrosion, they have been studying protective coating materials to use these coatings to combat marine corrosion and protect marine engineering equipment. It can be said that anti-corrosion coatings are key materials to ensure the safe service of marine engineering and mechanical equipment.

However, traditional flaky anti-corrosion coatings have problems such as large size, high thickness, large addition amount, and poor compatibility with the resin matrix. They have reached the limit of their service performance and are prone to cracking, peeling and failure during service in harsh marine environments. They cannot meet the anti-corrosion needs in complex marine environments.

Facing this challenge, the Ningbo Institute of Materials Technology and Engineering of the Chinese Academy of Sciences has developed a new generation of marine heavy-duty anti-corrosion coating materials . This coating is made of organic and inorganic fiber composite reinforced polymer resin, which can form a strong and tough protective layer.

Under the erosion of waves, inorganic fiber materials are like high-strength structural skeletons, which can effectively cope with the impact of waves and sediment erosion; organic fiber materials are like high-toughness tendons. They run through the coating, combining hardness and flexibility to form a strong and integrated protection network. This dense protection network can effectively block the spread of corrosion factors, while dispersing and transmitting the impact force of waves and reducing stress concentration in local areas.

Just like the bones and tendons of the human body, the entire polymer composite coating is made tougher. This "natural" bionic technology not only enhances the anti-erosion and wear resistance of steel pipe piles in the ocean, but also extends the maintenance cycle. With it, our marine equipment is like a layer of anti-corrosion and anti-change armor, with an indestructible golden body like Sun Wukong!

On March 21, 2023, the Shui Xinqi No. 1 piling ship slowly sank the steel pipe piles coated with this anti-corrosion coating into the sea. The 109-meter-long steel pipe piles penetrated directly into the seabed like a "stabilizing needle", which also marked the successful sinking of the first trial steel pipe pile of the Hangzhou Bay Cross-sea Railway Bridge.

Manufacturing of large-size high-strength steel pipe piles and their high-durability protective coatings

(Image source: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)

The pile-driving ship slowly sinks the steel pipe pile into the sea

(Image source: Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences)

You should know that the Hangzhou Bay Cross-sea Railway Bridge is one of the key projects of the Suzhou-Jiaxing-Ningbo High-speed Railway. This bridge is the world's longest and highest-standard high-speed railway cross-sea bridge, and is a milestone in the global bridge construction. The application of a new generation of marine heavy-duty anti-corrosion coating materials to this project not only represents the recognition of the quality of this material by the project party and the industry, but will also promote the research team to continue to move forward and develop more and better marine long-term anti-corrosion materials.

The most important equipment for a great country is made of materials. I believe that relying on the power of scientific and technological innovation, the Chinese people will be more determined to explore the deep blue. And to make every miracle created by the Chinese nation at sea stand forever and remain new for thousands of years will be the eternal pursuit of all researchers in our Key Laboratory of Marine Key Materials!