Which stainless steel grades perform best in chloride-containing solutions？

Stainless steel is widely used in industries such as chemical processing, marine engineering, and power generation due to its excellent corrosion resistance. However, different stainless steel grades have varying levels of resistance to chloride-containing environments, which can cause pitting, crevice corrosion, and stress corrosion cracking (SCC). This article provides an overview of several stainless steel grades and their suitability for chloride-containing solutions.

ASTM A182 Gr.F304 304L ASME B16.5 RF blind flange

1.304 and 304L Stainless Steel

304 stainless steel is the most common and cost-effective austenitic stainless steel. It is widely used in food processing, chemical plants, and nuclear industries. While it has good corrosion resistance in organic and inorganic media, it is highly susceptible to pitting and crevice corrosion in chloride-containing environments (e.g., cooling water).

304L has a lower carbon content (≤0.03%), which enhances intergranular corrosion resistance and weldability, making it ideal for partially or fully welded plate heat exchangers (PHEs).

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2.316 and 316L Stainless Steel

316 stainless steel contains approximately 2% molybdenum (Mo), which significantly improves its resistance to chloride-induced corrosion compared to 304. It is suitable for:

✔ Natural cooling water

✔ Cooling tower water

✔ Softened water

✔ Organic acids, dilute nitric acid (≤20%), and dilute phosphoric acid (≤30%)

316L has a lower carbon content (≤0.03%), providing better weldability and post-weld corrosion resistance.

3.317 Stainless Steel

317 stainless steel has a higher Cr, Mo, and Ni content than 316, offering better resistance to pitting, crevice corrosion, and SCC. It is ideal for applications requiring extended service life in harsh environments.

4.904L Stainless Steel (AISI 904L / SUS 890L)

904L is a high-performance austenitic stainless steel that balances cost and corrosion resistance. It is particularly suitable for sulfuric acid, phosphoric acid, and halides (Cl⁻, F⁻) due to its high Cr, Ni, and Mo content. It offers excellent resistance to pitting, crevice corrosion, and SCC.

5.Avesta 254 SMO and 654 SMO Stainless Steels

These are super austenitic stainless steels with enhanced Mo content, making them highly resistant to chloride-induced corrosion.

254 SMO is an improved version of 316, designed for saltwater and inorganic acid applications where 316 is insufficient.

654 SMO has even higher Cr, Ni, Mo, and N content, offering superior performance in cold seawater environments.

6.RS-2 Stainless Steel

RS-2 is a Chinese-developed Cr-Ni-Mo-Cu stainless steel with corrosion resistance similar to 316 but with better SCC resistance. It is suitable for concentrated sulfuric acid (90-98%) below 80°C, with an annual corrosion rate of ≤0.04mm/a.

7.Nickel-Based Alloys

Nickel-based alloys provide superior corrosion resistance compared to stainless steels.

Incoloy 825 (Ni 40%, Cr 22%, Mo 3%) is highly resistant to sulfuric acid and caustic solutions (50-70% NaOH) but is susceptible to chloride crevice corrosion.

31 Alloy is an improved version of 904L with increased Mo and N content, offering better corrosion resistance in 20-80% sulfuric acid at 60-100°C.

33 Alloy is a fully austenitic chromium-based stainless steel, comparable to Inconel 625, with excellent resistance to nitric acid and mixed acid solutions but unsuitable for reducing environments.

8.High-Performance Nickel Alloys

C-2000 Alloy (developed in the 1990s) offers the best overall corrosion resistance among these materials. It is superior to C-276 and C-22 in hot chloride solutions, dilute sulfuric acid, and phosphoric acid.

59 Alloy has 59% Ni content and is the best nickel alloy for corrosion resistance, thermal stability, formability, and weldability. Since its commercialization in 1990, it has been widely used in sulfuric acid, hydrochloric acid, hydrofluoric acid, and aggressive chloride environments.

Selecting the right stainless steel for chloride-containing solutions depends on the specific environmental conditions. 304 and 316 are common choices, but for aggressive chloride environments, higher alloyed stainless steels like 904L, 254 SMO, and nickel-based alloys provide superior corrosion resistance. Understanding these material differences helps industries optimize performance and longevity in chemical processing, marine, and offshore applications. Email:sales@haihaogroup.com