Application conditions of 31 alloy and 33 alloy stainless steels in chlorinated aqueous solutions

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1. The 31 alloy is an improved version of 904L (with increased Mo and N contents); it is a standard high-grade stainless steel containing 6% Mo (31% Ni-27% Cr-6.5% Mo-32% Fe). Better corrosion resistance in many media than 904L ； In sulfuric acid at concentrations of 20% to 80% and temperatures of 60°C to 100°C, its corrosion resistance even exceeds that of C-276. 2. 33 alloy: A fully austenitized chromium-based high-grade stainless steel whose corrosion resistance is comparable to that of certain Ni-Cr-Mo alloys such as Inconel 625. It exhibits good resistance to localized corrosion and stress corrosion cracking in acidic and alkaline media, including nitric acid and mixtures of nitric acid and hydrofluoric acid ； Its corrosion resistance in concentrated nitric acid is much better than that of 304L. For example, it is suitable for sulfuric acid with a concentration of over 96%–99%, a temperature of ≤150°C, and a sulfur oxide content of less than 200 mg/L ； Hot seawater ； Highly corrosive boiling solutions with a concentration of ≤50% ； Phosphoric acid with a concentration of ≤85% and a temperature of ≤150°C, etc. However, it is not suitable for reducing media (such as dilute sulfuric acid). The price is roughly the same as that of C-276.