Ferralium 255 – SD50 (UNS S32550)

Ferralium 255 is a super duplex stainless steel in the Ferralium family. It was the first super duplex stainless steel. Developed by Langley Alloys to meet the needs of the oil, gas and chemical industries, Ferralium 255 achieves higher strengths than most other stainless steel varieties and corrosion-resistant alloys. It is resistant to chloride SCC, as well as crevice corrosion and pitting. Furthermore, it features double the yield strength of Alloy 20.

As a 25% Cr alloy, with significant additions of copper, Ferralium® 255 offers excellent corrosion resistance in a wide variety of corrosive chemicals. This includes sulphuric, nitric and phosphoric acid. Ferralium 255 contains 2% copper, which is more than other super duplex grades. As a result, Ferralium 255 features better resistance to acids than most other alloys. 

However, it is not only the oil, gas, and chemical industries where Ferralium 255 thrives. Ferralium 255 also provides outstanding resistance to pitting and crevice corrosion in seawater and other chloride-rich environments, making it an excellent material for use in marine environments. This resistance has several contributing factors. The first of these is because the Critical Pitting Temperature of Ferralium 255 exceeds 50°C. At the same time, Ferralium 255 features excellent ductility and impact strength at both ambient and sub-zero temperatures. These, combined with high resistance to abrasion, erosion and cavitation erosion, ensure outstanding resistance.

Ferralium 255 was listed in NACE MR 01 75 for sour service. Having gained ASME Approval for Pressure Vessel applications, Ferralium 255-SD50 was tested to the highest degree using tests designed to guarantee that the trade-marked product possesses high integrity, a correct phase balance, and the absence of sigma and other deleterious phases. Ferralium 255 is less sensitive to the formation of these deleterious phases than other super duplex stainless steels.

Since its original development and patent by Langley Alloys in the 1960s, Ferralium 255 has been used successfully in some of the most demanding applications worldwide. With a yield Strength >85ksi, it remains the highest strength super duplex grade available in a solid bar. It can also be offered in the Aged and Fastener Grade condition.

Ferralium 255-SD50 is available for immediate delivery in 40 different sizes, from 0.5” (12.7mm) to 14” (304.8mm) in diameter. Our efficient processing facilities can provide accurately cut pieces. Extra testing, inspection and processing are all available in-house.