Experiences With Duplex Stainless Steels in Offshore Grating Systems

Structures located in challenging marine environments play a vital role in several sectors, including offshore wind and oil and gas exploration. These environments expose structures to seawater, airborne chlorides from sea spray, and humid coastal regions. Offshore structures are expected to have a long service life due to limited access for inspection and maintenance. Corrosion is one of the major challenges marine structures face due to chloride-rich environments, wet-dry cycles, high humidity, and microbiological attacks. Material selection and protection methods are critical to ensuring reliability, minimizing maintenance, and extending the service life of marine structures. Duplex stainless steels have been widely used in marine environments for their strength and corrosion resistance. Compared to conventional austenitic stainless steels, duplex grades provide high strength in the solution-annealed condition, enabling the design of lighter structures with thinner gauges. Grating systems are often found on offshore installations, from oil and gas rigs to offshore wind farms. and can be cost-effectively constructed in duplex alloys. Forta EDX 2304, Forta DX 2205 and Forta LDX 2101 have been successfully installed in seaside environments, where their strength and improved corrosion allowances permit thinner sections and weight savings. Improved localized corrosion resistance in chlorides, meaning increased pit and crevice corrosion resistance, suggests that service life can be greatly improved, and maintenance needs are diminished. The objective of this paper is to share past experiences with duplex gratings in offshore structures and describe the rationale behind the selection of this class of materials.