The marine environment presents multiple corrosion incentives such as high salinity, high pressure, sulfur-containing media, and temperature fluctuations. Under such conditions, ordinary steel is prone to pitting corrosion, crevice corrosion, and stress corrosion cracking, seriously affecting equipment lifespan and operational safety. High-temperature alloys, with precise composition design and excellent comprehensive performance, have become core materials for solving corrosion challenges in marine engineering, providing reliable support for deep-sea development, seawater desalination, and other fields.
Nickel-based superalloys are the mainstay in corrosion-resistant applications in marine engineering, and their corrosion resistance stems from the synergistic effect of the nickel-chromium matrix and trace elements. Inconel 625, as a classic grade, is based on a nickel-chromium matrix with additions of molybdenum, niobium, and other elements. The dense oxide film formed by chromium can resist chloride stress corrosion, while molybdenum enhances resistance to reducing media. Its pitting corrosion resistance in seawater environments far exceeds that of 316 stainless steel. The subsea gas production system of Equinor in Norway uses this alloy flange, which has been in service for 20 years without any records of corrosion failure, fully demonstrating its reliability.
Hastelloy C-276 exhibits outstanding performance in complex corrosive environments. As a nickel-molybdenum-chromium alloy, it exhibits strong resistance to strong oxidizing and reducing acids, as well as high chloride ion media, effectively avoiding pitting and crevice corrosion. In the high-pressure and high-salt environment of deep-sea oil and gas exploration, its pipeline components can stably withstand extreme operating conditions. Compared to titanium alloys, it exhibits more stable performance in high-temperature acidic environments and is widely used in pumps, valves, and pipeline systems on offshore platforms.
Precipitation-strengthened high-temperature alloys further balance corrosion resistance and high strength, with N08925 (Incoloy 925) being a typical representative. This alloy achieves strengthening through the precipitation of γ’ phase from titanium and aluminum, and the low carbon content reduces the precipitation of welding carbides. In acidic oil and gas environments containing H₂S/CO₂, the annual corrosion rate can be controlled within 0.05mm, which is far superior to traditional stainless steel. In the East China Sea oil and gas field project, the lifespan of downhole tools made from this alloy is extended by more than three times compared to the original materials, significantly reducing the risk of unplanned production downtime.
Furthermore, MONEL K500 alloy is indispensable in the field of shipbuilding. After undergoing age-hardening treatment, it exhibits both high strength and resistance to seawater corrosion and marine biofouling. When used in components such as ship shafts and propellers, it can reduce the failure rate by 60%. In seawater desalination plants, high-temperature alloy evaporator tube bundles can withstand high chloride ion concentrations, extending the equipment replacement cycle to 15 years and significantly improving operational efficiency.
As marine engineering progresses towards deeper waters, higher temperatures, and greater pressures, the performance requirements for high-temperature alloys continue to escalate. In the future, through component optimization and process innovation, high-temperature alloys will expand their application scenarios while maintaining both corrosion resistance and cost-effectiveness, providing core material support for the safe and efficient advancement of marine resource development.
