The ocean harbors abundant natural resources, and its development not only has significant economic importance but also reflects a country’s technological and research capabilities. With the increasing intensity of marine development, the number of offshore industrial facilities, such as subsea oil pipelines, deep-sea drilling platforms, and offshore bridges, is rising year by year. However, the harsh corrosive conditions of the marine environment can cause severe corrosion to marine metal components. According to statistics, the economic losses caused by corrosion worldwide in 2016 accounted for 3.4% of global GDP, with marine structures accounting for a third of this loss. Therefore, understanding the characteristics of marine corrosion and selecting suitable methods for protecting offshore metal components are of particularly significant economic value.

Characteristics of Marine Environment Corrosion

Seawater contains a large amount of salt, making it an excellent electrolyte solution with high electrical conductivity. As a result, metal structures exposed to this environment are subject to severe corrosion. Marine corrosion environments can be categorized into several regions based on the unique characteristics of the marine environment:

レーザークラッディング テクノロジー

Application of Laser Cladding Technology in Marine Corrosion Protection

S355 steel, commonly used in marine environments, exhibits mechanical properties similar to Q345 steel. Structures made from S355 steel are highly susceptible to corrosion in marine environments. By applying an Al-Ni-TiC-CeO2 composite cladding layer to the surface of S355 steel, experimental results show that with a cladding scan speed of 7.5 mm/s, a dilution rate of less than 5% can be achieved. Polarization curves of samples with different cladding scan speeds (6, 7, 7.5, 8 mm/s) reveal that the sample cladded at 7 mm/s has the highest corrosion resistance, showing a higher self-corrosion potential and lower self-corrosion current density. Compared to untreated S355 steel, the cladded steel shows significantly enhanced corrosion resistance. The Al-Ni-TiC-CeO2 composite cladding layer not only improves the corrosion resistance of the base material but also enhances its wear resistance and hardness, significantly increasing the material’s service life.

In coastal areas, watergate hydraulic lifting pistons are exposed to the splash zone and tidal zone, where corrosion conditions are severe. Conventional surface treatment techniques like flame spraying and plasma spraying often suffer from high porosity and poor bonding strength. In contrast, laser cladding using iron-based, nickel-based, or cobalt-based alloy powders can improve the corrosion resistance of the piston rods, with the technology potentially replacing traditional nickel and chrome plating methods as a new corrosion protection solution.

In nuclear power plants, seawater pumps’ impellers are prone to corrosion and cavitation erosion when submerged in seawater. To address this, three types of alloy cladding powders were applied to improve the corrosion resistance of 316 stainless steel. The results showed that when the alloy powders contained high chromium and high nickel, the cladded layer, consisting of austenite with a small amount of martensite, significantly alleviated the corrosion issues faced by the impellers.

Overall, alloy powders can be tailored to the specific corrosion environment of metal components to improve their corrosion resistance. For example, stainless steel materials can be used in the marine atmospheric zone, while nickel-based powders with wear-resistant components can be added for use in splash zones or tidal zones to enhance material adaptability in these areas.

Drawbacks of レーザークラッディング テクノロジー

Surface Roughness: The cladded layer may have a rough surface, requiring machining if the surface finish is critical for the application.

Uniformity and Stability: The uniformity of the cladded layer, product stability, and the supporting equipment may not yet meet industrial production requirements.

Theoretical Research Gaps: There is insufficient systematic research on alloy solidification, internal material changes, and the temperature field of the cladded layer.

結論

As human exploration of the ocean deepens, more metal equipment and components will be used in marine environments. Understanding the characteristics of marine corrosion and developing effective protection methods is crucial. Laser cladding technology can be applied to produce corrosion-resistant alloy cladding layers for metal components, playing an indispensable role in future marine corrosion protection. This technology will continue to contribute significantly to the protection of marine infrastructure and the advancement of marine engineering.