S31500 / EN 1.4424 is the first generation of duplex stainless steel, with high chromium content, sufficient Mo and Ni, and good corrosion resistance in oxidizing acid and moderate reducing acid media. However, it contains ferrite, which is sensitive to hydrogen embrittlement, and the corrosion resistance of duplex stainless steel in hydrogen-containing environments is not high. In the range of acid concentration of at least 40%, S31500 / EN 1.4424 is better than 316 and 317 steels; it is resistant to oxidizing acid corrosion containing chlorides; in medium-concentrated sulfuric acid or hydrochloric acid, S31500 / EN 1.4424 has insufficient nickel content and poor corrosion resistance. The oxidative corrosion resistance of S31500 / EN 1.4424 makes it an excellent candidate material for nitric acid equipment and strong organic acids. The high chromium content and the presence of ferrite phase have good corrosion resistance in alkaline media. S31500 / EN 1.4424 has excellent mechanical properties, high strength and good plasticity and toughness. Its plastic-brittle transition is smoother than that of carbon steel or ferritic stainless steel, and its plasticity is good at -40°C.