[ Mining / Duplex ]
[ Mining / Duplex ]
Duplex – ideal for deep-sea mining equipment
Duplex stainless steel is a cost-effective material for the deep-sea environment, suitable for equipment such as subsea pipelines, flowlines, umbilicals, risers, offshore platforms, marine structural components, marine hardware, valves, fittings, and desalination systems.
By Srikumar Chakraborty, ex ASP / SAIL, Freelance Consultant
The National Oceanic and Atmospheric Administration remotely operated underwater vehicle Deep Discoverer explores the seabed near Puerto Rico. Source: https:// oceanexplorer. noaa. gov / okeanos / explorations / ex1502 / dailyupdates / apr11. html
Deepsea minerals Critical minerals such as lithium, cobalt, nickel, and rare earth elements play an indispensable role across a broad spectrum of industries, powering technologies from wind turbines and electric vehicles to smartphones, medical devices, and military systems. While land-based extraction of these resources is well established, rapidly growing demand is driving renewed interest in the vast, mineral-rich deposits found on the ocean floor. Several nations have already begun investigating subsea mineral resources and evaluating emerging deep-sea mining techniques. Nevertheless, much of the deep ocean remains poorly understood and largely unexplored. The prospect of commercial deep-sea mining remains highly controversial, with scientists and environmental groups raising serious concerns about the potential impacts on marine ecosystems and broader planetary health.
Charaterististics of seawater Marine and subsea environments present distinct material challenges arising from salinity, variable density, temperature fluctuations, and the presence of dissolved compounds. Seawater consists of approximately 96.5 % water and 3.5 % dissolved salts, primarily sodium chloride( NaCl), along with notable concentrations of magnesium, sulfate, calcium, and potassium. It also contains dissolved gases, including oxygen, nitrogen, and carbon dioxide. Salinity plays a critical role in influencing key physical properties of seawater, such as density, freezing point, and chemical reactivity, all of which can affect both material performance and interactions with marine life. Moreover, density is further modulated by temperature, with colder waters exhibiting higher density— an important consideration in the design and longevity of materials exposed to deep-sea conditions.
Progress of deep-sea mining Countries including China, Japan, South Korea, France, and Norway are actively pursuing deep-sea mining, holding or seeking exploration licenses from the International Seabed Authority( ISA) under the United Nations Convention on the Law of the Sea( UNCLOS). Established in 1994, the ISA regulates mining activities in international waters, balancing resource development with environmental protection for the benefit of humanity. Interest in deep-sea mining is driven by growing demand for critical minerals used in electric vehicle batteries, renewable energy infrastructure, electronics, and metal industries. Targeted resources include polymetallic nodules, seafloor massive sulfides,
and cobalt-rich crusts, which contain valuable metals such as manganese, nickel, cobalt, copper, and rare earth elements. Deep-sea mining remains in the exploration phase, with no commercial operations to date. While the ISA has issued exploration contracts, regulations for full-scale exploitation are still under development. China has emerged as a key player, securing multiple ISA contracts and investing heavily in deepsea mining technology. Supported by strong state backing, China leads in exploration efforts but faces scrutiny over environmental impacts and evolving international regulations.
What is duplex? Duplex stainless steels are distinguished by their two-phase microstructure, comprising approximately equal proportions of austenite and ferrite. While the nominal target is a 50 / 50 distribution, commercial alloys typically exhibit slight variations, with phase balances generally falling within the 40 / 60 range. Duplex stainless steels offer corrosion resistance comparable to austenitic grades but provide superior resistance to stress corrosion cracking— particularly in chloride-rich environments— alongside significantly higher tensile and yield strengths, with yield strength approximately double that of standard austenitic stainless steels.
www. stainless-steel-world. net Stainless Steel World November 2025 23