The Norwegian economy is built on the sea. Two pillars – oil and gas (offshore) and aquaculture (aquaculture) – drive national prosperity, but they operate in one of the world’s most hostile environments. Here, in the North Sea and along the coast, the battle against nature is constant. The biggest enemy is not the storms, but the silent, invisible attack of salt water – specifically chlorides.
For executives and CFOs in these sectors, material selection is not a technical detail – it is a fundamental part of risk management. A wrong choice can lead to catastrophic failures, downtime and losses in the billions. While many people are familiar with “acid-resistant” steel, there is another, specialized group of materials that is the real key to long-term success: Duplex steel.
The hidden risk- when “acid-proof” is not enough
In many industries, standard stainless steel, such as 316L (often called “acid-resistant” or “marine grade”), is an excellent choice. But the North Sea is not “many industries”. The aggressive, cold and chloride-rich seawater reveals the critical weakness of 316L pitting .
Pit corrosion is not just a cosmetic problem. It is a local, insidious form of corrosion that drills small, deep holes in the surface of the steel. These holes can quickly compromise the structural integrity of a pipe, tank, or critical component. Add to that the mechanical stresses of surges and drift, and you also risk stress corrosion cracking – a combination that can lead to sudden and catastrophic failure.
For an oil platform or a fish cage, “sudden failure” are words that keep management awake at night.
Duplex benefits that define resiliency
Duplex steel gets its name from its microstructure, which is a mixture (or “duplex”) of two types of steel- austenite and ferrite. This hybrid structure provides a combination of properties that make it ideal for marine applications:
1. Superior chloride resistance: This is the most important factor. Resistance to pitting corrosion is often measured with a PREN (Pitting Resistance Equivalent Number) value . While 316L has a PREN value of around 24-26, standard duplex grades (like 2205) start at around 35, and super-duplex (like 2507) have values above 40. This superior chemistry provides a robustness against chloride attacks that the 316L simply can’t match.
2. Double the strength and lower weight: Duplex steel is about twice as strong as the standard 316L. For a CFO or engineer, this is a huge advantage. Higher strength means that the same structural integrity can be achieved with thinner material. This leads to significant weight loss. On an offshore platform, where every kilogram of “topside” weight costs a fortune to support, weight reduction equals direct cost savings.
An investment in reliability- not a cost
Let’s look at the commercial reality. Yes, the initial purchase price for duplex steel is higher than for 316L. But focusing on purchase price alone is a classic fallacy. What counts is total life cycle costs (LCC).
For offshore (Oil & Gas): What is the cost of one day of unplanned shutdown on a production platform? Million. What does a leak from a corroded pipe system cost – in both money and reputation? Erratic. The investment in super-duplex for critical systems (such as seawater cooling, fire extinguishing systems or pipelines) is an insurance premium against catastrophic failure.
For aquaculture (aquaculture): The industry is under constant pressure to improve sustainability and safety, especially related to escapes. A structural collapse in a fish farm cage – caused by corrosion in a critical component – is a financial and reputational nightmare. By using duplex steel in load-bearing structures, mooring systems and feed barges, the farmer invests directly in operational safety and risk reduction.
Conclusion- Strategic choice for an ocean economy
The Norwegian ocean economy thrives in spite of, not because of, its surroundings. In this extreme environment, the choice of materials is a strategic decision that directly affects the company’s bottom line and risk profile.
To choose standard stainless steel where duplex is required is to accept a planned failure in the future. Choosing duplex is a long-term investment in uptime, security, and profitability.
Just as important as the choice of duplex itself, is the choice of supplier. Ensuring materials with correct and full traceability (certification) is absolutely necessary. This requires a specialised steel partner who understands the extreme requirements of the North Sea and can guarantee the quality of every delivery.
