Applicable conditions of several stainless steels in chlorinated aqueous solutions

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1 304 stainless steel is the cheapest and most widely used austenitic stainless steel (used in industrial equipment such as those in the food, chemical, and nuclear industries). Suitable for general organic and inorganic media. For example, nitric acid with a concentration of <30%, temperature ≤100°C, or a concentration of ≥30% and temperature <50°C ； Carbonic acid, ammonia water, and alcohols of various concentrations at temperatures ≤100℃. Poor corrosion resistance in sulfuric acid and hydrochloric acid ； It is particularly sensitive to crevice corrosion caused by chlorinated media (such as cooling water). The corrosion resistance and applications of 2 304L stainless steel are essentially the same as those of 304 stainless steel. Due to its lower carbon content (≤0.03%), it exhibits better corrosion resistance (especially against intergranular corrosion, including in the weld area) and weldability, making it suitable for semi-welded or fully welded PHEs. Type 3316 stainless steel is suitable for general organic and inorganic media. For example, natural cooling water, cooling tower water, softened water ； carbonic acid ； Acetic acid and caustic alkali solutions with a concentration of <50% ； Alcohols and **solvents ； Dilute nitric acid at a temperature of ≤100°C (concentration <20%), dilute phosphoric acid (concentration <30%), etc. However, it is not suitable for sulfuric acid. Due to its approximately 2% Mo content, it has better corrosion resistance in seawater and other chlorinated media than type 304, and can fully replace type 304. The corrosion resistance and applications of 4 316L stainless steel are basically the same as those of 316 stainless steel. Due to its lower carbon content (≤0.03%), it has better weldability and corrosion resistance after welding, making it suitable for semi-welded or fully welded PHEs. Type 5317 stainless steel is suitable for applications that require a longer service life than type 316. Due to slightly higher contents of Cr, Mo, and Ni elements compared to type 316, it exhibits better resistance to crevice corrosion, pitting, and stress corrosion. 6 AISI 904L or SUS 890L stainless steels are cost-effective austenitic stainless steels that balance price and corrosion resistance; they offer better corrosion resistance than the aforementioned materials, making them particularly suitable for use in acids such as sulfuric acid and phosphoric acid, as well as halides (containing Cl— and F—). Due to its high contents of Cr, Ni, and Mo, it exhibits excellent resistance to stress corrosion, pitting, and crevice corrosion. 7 Avesta 254 SMO is a super-low carbon high-grade stainless steel that represents an improvement over type 316 through an increased Mo content; it boasts excellent resistance to chloride pitting and crevice corrosion, making it suitable for use in saline solutions, inorganic acids, and other media where type 316 is not appropriate. 8 Avesta 654 SMO is a super-low carbon high-grade stainless steel with higher levels of Cr, Ni, Mo, and N compared to 254 SMO; it exhibits better resistance to chloride corrosion than 254 SMO and can be used in cold seawater. 9 RS-2 (OCr20Ni26Mo3Cu3Si2Nb) stainless steel is a domestically produced Cr–Ni–Mo–Cu stainless steel. Its resistance to pitting and crevice corrosion is equivalent to that of type 316, while its resistance to stress corrosion is better. It can be used with concentrated sulfuric acid (concentration 90–98%) at temperatures below 80 °C, with an annual corrosion rate of ≤0.04 mm/a. 10 Incoloy 825(S) is a high-grade stainless steel composed of Ni (40%)–Cr (22%)–Mo (3%). Incoloy is a registered trademark of Thennational Nickel Co. Suitable for sulfuric acid of various concentrations at low temperatures ； It exhibits good corrosion resistance in caustic alkali solutions (such as NaOH) with concentrations of 50% to 70%, and does not suffer from stress corrosion cracking. However, it is highly sensitive to crevice corrosion caused by chlorides. Furthermore, its stamping performance is also poor, so it is not a commonly used material for sheets. The 11 31 alloy is an improved version of 904L (with increased Mo and N contents), as well as 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. 12 33 alloy is a fully austenitized chromium-based high-grade stainless steel, whose corrosion resistance can compare with 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. 13 C-2000 alloy is a nickel-based alloy developed in the 1990s; its price is similar to that of C-276, and it is one of the materials with the best corrosion resistance among those listed. In media such as sulfuric acid at concentrations below moderate levels, dilute hydrochloric acid, phosphoric acid at concentrations ≤50% at boiling temperature, and hot chlorides, its corrosion resistance is better than that of C-276 and C-22, showing a tendency to replace C-22 alloys. However, for sulfuric acid with a concentration of ≥70%, its corrosion resistance is inferior to that of C-276. The chemical composition of the 14 59 alloy is essentially the same as that of C-2000, with the exception of a slightly higher Ni content (59%), lower Fe levels, and the absence of Cu and W. It is currently the nickel-based alloy with the best corrosion resistance, thermal stability, formability, and weldability. Since its commercialization in 1990, it has been widely used in sulfuric acid, hydrochloric acid, hydrofluoric acid, as well as many other media containing chlorine, oxygen, and at low pH levels