Thread Content
The development directions and key focuses for offshore engineering equipment and high-tech ships over the next decade lie mainly in the following areas: (1) Equipment for ocean resource exploitation； (2) Equipment for the development of marine spatial resources ； (3) Comprehensive testing and inspection platform ； (4) High-tech ships ； (5) Core supporting equipment. To achieve the strategic goals of \"Made in China 2025\" and accelerate the improvement of the industrial technology level of China’s offshore engineering equipment and high-tech ships, it is essential to pay attention to the corrosion resistance of such equipment in order to ensure their quality and performance. The ocean is a harsh corrosive environment, mainly because seawater contains abundant mineral salts, which easily lead to the formation of galvanic cells with metal-made marine equipment, resulting in microscopic corrosion. Furthermore, many organisms in the ocean attach to the equipment’s structure, which not only reduces its operating speed but also secretes organic acids or produces highly corrosive substances such as sulfur dioxide and hydrogen sulfide, thereby causing multi-scale composite damage to the equipment from a microscopic to a mesoscopic and then to a macroscopic level. Corrosion characteristics vary depending on the area affected by corrosion. The main forms of corrosion include uniform corrosion, pitting corrosion, crevice corrosion, impact corrosion, cavitation corrosion, abrasion, galvanic corrosion, and so on. These types of corrosion are often related to the structural design or metallurgical properties of marine equipment. The factors that cause corrosion of equipment in the ocean mainly include chemical factors, physical factors, biological factors, regional factors, pressure factors, and erosion factors. In addition to corrosion, marine equipment also has to dive and surface repeatedly in different marine areas, which exposes it to various forms of mechanical wear and damage. For example, as the depth of penetration increases, the amplitude of the alternating load also grows, making it inevitable for the base material to suffer from low-cycle fatigue. Due to factors such as pitting, the critical condition for mechanical damage to the matrix material becomes increasingly lower. Therefore, to ensure the safe operation and service life of marine equipment, it is particularly important to protect the material of the equipment’s substrate through necessary technical measures. For the surface protection of matrix materials used in marine equipment, it is achieved mainly through three approaches: (1) Surface treatment to enhance the corrosion resistance and fatigue resistance of the matrix ； (2) Using cathodic protection to provide corrosion resistance to the base material ； (3) Provide comprehensive protection for the matrix material through coating methods. 1. The application of substrate surface treatment in matrix material applications: For example, in China’s deep-submergence vehicles, high-strength, high-toughness, weldable pressure-resistant shell steel with a yield strength of not less than 785 MPa is used. Special metal surface treatment techniques have **improved the steel’s resistance to seawater corrosion and compressive stress.** 2. Application of cathodic protection: Due to the inherent properties of steel, it can resist corrosion to a certain extent and within certain limits, but this is not sufficient to meet anti-corrosion requirements. Therefore, other necessary anti-corrosion measures must be taken for the steel substrate. Cathodic protection is a method for protecting a material substrate from an electrochemical perspective; its basic principle is to supply a certain amount of electrons to the metal being protected, keeping it in a reduced state thereby providing protection. 3. Application of coating protection methods: Although cathodic protection can reduce electrochemical corrosion to a certain extent, it often fails to prevent chemical corrosion caused by marine organisms, and it is not possible to completely isolate the base material from the corrosive environment. Therefore, applying an external coating is particularly important. Current ship protection measures also primarily rely on a combination of cathodic protection and coating protection. As ocean pollution continues to increase, the marine environment becomes more complex, which in turn makes the problem of metal corrosion in this environment more prominent. In the future, higher requirements will inevitably be placed on the corrosion resistance of marine equipment.