Current research status on the corrosion behavior of 316L and 2205 stainless steels

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This post was last edited by Wang Genrong on 2016-7-22 at 15:30. The pitting, crevice, stress corrosion, and corrosion fatigue resistance of duplex stainless steels are significantly better than those of ordinary austenitic stainless steels, and they can compare with high-alloy austenitic stainless steels. Furthermore, the yield strength of duplex stainless steel can reach 400–550 MPa, which is twice that of ordinary stainless steel; thus, it allows for reduced material usage and lower costs in equipment manufacturing. Due to its unique advantages, duplex stainless steel is widely used in various industrial fields such as petrochemical equipment, seawater and wastewater treatment systems, oil and gas pipelines, and papermaking machinery. In recent years, it has also been explored for use in bridge load-bearing structures. However, duplex stainless steel still retains the various brittleness tendencies of high-chromium ferritic stainless steel, and is not suitable for use in operating conditions above 300°C. Therefore, in certain medium environments with harsh low-temperature conditions, duplex stainless steel may gradually replace 316L and austenitic stainless steel, becoming a focus for new types of black materials. Numerous studies have been conducted both domestically and internationally to investigate the feasibility of using duplex stainless steel as a replacement for 316I, an austenitic stainless steel. Many studies have shown that under the same conditions, 2205 duplex steel has a lower corrosion sensitivity than 316L austenitic steel, for various reasons. Due to its two-phase structure of α + Y phases, duplex stainless steel possesses properties that are a combination of those of austenitic and ferritic stainless steels. Compared to austenitic stainless steels, it has higher strength, particularly a significantly increased yield strength; as a result, its resistance to intergranular corrosion, stress corrosion, and corrosion fatigue is markedly improved. Recently, several new grades of duplex stainless steel have been developed. The following introduces a few newly developed duplex stainless steels other than SAF2205 [1]. (1) SAF2707: To improve the operational performance of heat exchangers under harsh corrosion conditions and extend their service life, Sandvik has developed a new type of super duplex stainless steel called Sandvik SAF2707. This steel grade is mainly used in the chemical, petrochemical, and refining industries. This steel grade was developed primarily to meet the requirements of higher operating temperatures and longer operational times (service life) for heat exchangers, while ensuring the reliability, safety, and performance of the equipment. (2) YUS DX1, a high-strength and highly corrosion-resistant duplex stainless steel developed by Nippon Steel Corporation, exhibits better resistance to pitting and crevice corrosion than SUS 316 and SUS 317. Its yield strength at room temperature is twice that of SUS 304 and SUS 316 steels; it also has greater resistance to stress corrosion compared to SUS 304 steel. Its weldability is similar to that of common austenitic stainless steels. (3) A duplex stainless steel of Korean patent type, which possesses excellent thermoplasticity, resistance to high-temperature oxidation, corrosion resistance, and impact toughness. Its main components are: 22%–27% Cr, 5.0%–8.0% Ni, 2.0%–5.0% Mo, 2%. 0%–5.0% W, Cu less than 2.0%, 0.13%–0.30% Ni; suitable for marine facilities. Due to factors such as price and production volume, domestically used industrial production lines that employ duplex stainless steel still primarily rely on the domestically produced 2205 grade. Conclusion: Compared with 2205 duplex stainless steel, 316L austenitic stainless steel has its own advantages and disadvantages. In the production process, the selection of stainless steel materials should take into full account the potential for various types of corrosion; research methods should be continuously improved throughout the research process, and new materials should be continually discovered. Due to its excellent resistance to chloride corrosion and pitting corrosion, high mechanical properties, as well as lower manufacturing costs, duplex stainless steel is beginning to replace currently unsuitable corrosion-resistant steel components and some commonly used high-chromium-nickel stainless steels. Therefore, it is entirely possible for 2205 duplex stainless steel to replace 316L stainless steel in certain low-temperature environments. It is expected that duplex stainless steel will have significant application prospects in the petrochemical industry, offshore engineering, offshore drilling platforms, ships, and military equipment in the southeastern coastal areas.