Common Grades and Chemical Compositions

The commonly used corrosion – resistant alloys in the Chinese and South American (such as Brazil and Chile) markets mainly include: duplex stainless steels (Duplex, typically 2205/S32205 and 2507/S32750), austenitic stainless steels (Stainless, typically 304 and 316L), and nickel – based alloys (such as Inconel 625/UNS N06625 and Incoloy 825/UNS N08825). The main elemental compositions of each grade are as follows:

Market Prices (Q3 2025)

• ​Duplex steel 2205​​: The market price in China is about 24,000–26,500 yuan/ton (about 24–27 yuan/kg). There is no public quotation in the South American market, but it can be referred to the general price of corrosion – resistant steels, which may be at the level of several thousand US dollars/ton.

• ​​Super duplex steel 2507​​: The price in China is significantly higher than that of 2205, generally exceeding 30,000 yuan/ton, and the specific price is affected by production capacity and specifications. There is no public data in the South American market.

• ​​Stainless steel 304​​: The price of cold – rolled plates in China is about ¥13,000–15,000/ton, and the price of hot – rolled plates is at a similar level. The price of rough – rolled coils in South American markets (such as Brazil and Chile) is about US$2,343/ton (equivalent to about ¥16,000/ton).

• Stainless steel 316L​​: The price of hot – rolled plates in China is about ¥24,800–28,000/ton. There is relatively little data in the South American market. It can be inferred that the price is higher than that of 304, at about US$2,500–3,000/ton (the cost structure is similar, and currency fluctuations have a great impact).

• ​​Inconel 625​​: Globally, in the first quarter of 2025, the price of profiles and sheet materials is US51,000–56,000/ton(≈¥370,000–410,000/ton).ThelocalmarketsituationinChinaisusuallyatasimilarlevel,atabout¥350–410yuan/kg.TheimportpriceinSouthAmericashouldbeclosetotheinternationalprice(aboutUS50–60/kg).

• ​Incoloy 825​​: The common FOB quotation in China is roughly US$18–45/kg (i.e., ¥126–315 yuan/kg, or ¥126,000–315,000/ton). The average prices of bars, plates, and small – diameter pipes within this range are different. The South American market can refer to similar US dollar prices.

• Performance Advantages and Disadvantages

• ​​2205 Duplex steel​​: It has high strength and excellent toughness. The typical tensile strength σ_b ≈ 655 MPa and yield strength σ_0.2 ≈ 450 MPa. It combines the advantages of austenitic and ferritic structures and has strong resistance to stress corrosion cracking (especially in chlorinated media) and pitting corrosion. However, it has rapid work – hardening, is difficult to cold – form, and is more brittle and hard than austenitic steels. Strict temperature and strain control are required during welding, and subsequent solution annealing is necessary.

• ​2507 Super duplex steel​​: It has a higher content of alloying elements, so it has better strength and corrosion resistance than 2205 (but its toughness is slightly inferior at high temperatures). It has extremely strong resistance to chloride corrosion, pitting corrosion/pitting – crevice corrosion, and also has a high thermal conductivity and a low thermal expansion coefficient, with excellent resistance to intergranular corrosion. However, it has a high content of nickel, molybdenum, and chromium, resulting in a high cost. Its toughness will decrease after long – term use at high temperatures (> 570°C), and it is more difficult to process and weld.

• ​​304 Stainless steel​​: It has an austenitic structure, good plasticity and weldability, and is easy to process and form. It has good corrosion resistance under general working conditions (in oxidizing media). However, its resistance to localized corrosion is general, and it is prone to pitting corrosion in chlorinated environments and is not suitable for media with high chloride ion concentrations. Its mechanical properties are moderate (σ_b ≈ 520 MPa, with high plasticity), but its strength is lower than that of duplex steels. Its high – temperature resistance is better than that of ordinary carbon steels but not as good as that of high – chromium heat – resistant steels.

• ​316L Stainless steel​​: Compared with 304, it contains 2–3% Mo, which can significantly improve its resistance to chloride pitting corrosion/pitting – crevice corrosion. It has excellent corrosion resistance (especially in seawater, hydrochloric acid, and sulfuric acid environments) and good high – temperature oxidation resistance. The low carbon content (≤ 0.03%) prevents sensitization after welding. However, its price is higher than that of 304, and its processing hardness is slightly higher. Caution is still required in some extreme acids (such as concentrated nitric acid).

• ​​Inconel 625​​: It is a nickel – chromium – molybdenum high – temperature alloy with high strength, high plasticity, and high toughness. It has no precipitation hardening and has a strength level of σ_b > 800–1000 MPa at room temperature (after solution treatment). It has extremely excellent corrosion resistance and can resist oxidation, carburization, and various media corrosions at almost all temperatures (it performs very well in resisting chloride pitting corrosion, pitting – crevice corrosion, and stress corrosion cracking). It can resist the corrosion of various acids such as nitric acid, sulfuric acid, phosphoric acid, and hydrochloric acid and has corrosion fatigue resistance in seawater environments. It has good weldability and can be used for thick or thin – walled structures. However, it is expensive, has a high density, a higher thermal expansion coefficient than steel, and poor machinability. Special tools and processes are required.

• Incoloy 825​​: It is a nickel – iron – chromium – based alloy. With a high Ni content (about 38–46%), and the addition of Mo, Cu, Ti and other elements, it has excellent corrosion resistance to both oxidizing and reducing media. It is particularly resistant to the corrosion of strong acids such as sulfuric acid and phosphoric acid and is not prone to stress corrosion cracking in chlorinated environments. Its austenitic structure is stable and does not sensitize after welding. Its mechanical strength is moderate (far lower than that of Inconel 625) and is mainly used in the chemical industry with high corrosion resistance requirements. However, it has a high cost, general processability (it is brittle and hard to cut), and a lower heat – resistant strength than high – temperature alloys. It is not used for high – temperature structural parts.
• Typical Application Fields

• ​2205 Duplex stainless steel​​: It is widely used in occasions requiring high strength and chloride – corrosion resistance, such as petroleum and natural gas pipelines, chemical equipment, and heat exchangers. It is also used in offshore platforms, compressor components, seawater desalination equipment, and sewage treatment systems.

• 2507 Super duplex steel​​: It is used in pressure vessels, reactors, heat exchangers, and submarine pipelines in chemical processes (with high – chloride – ion media), petrochemicals, and deep – sea oil extraction projects. Its excellent chloride – corrosion resistance and high strength make it suitable for harsh environments.

• ​​304 Austenitic stainless steel​​: It is the most widely used and is suitable for general occasions such as chemicals, food, medical equipment, and household decorations. It is commonly used in kitchen utensils, building decorations, food processing equipment, general chemical containers, and food – grade pipelines. It has a high cost – performance ratio in low – corrosion environments.

• 316L Austenitic stainless steel​​: Due to its good resistance to seawater and strong acids, it is often used in chemicals (acid pickling, hydrochloric acid media), marine equipment, pharmaceuticals, and medical devices. Typical applications include seawater cooling systems, pharmaceutical equipment, hospital interiors, chemical plant components, and heat – exchanger pipes in thermal power and nuclear power plants.

• Inconel 625 Nickel – based alloy​​: With its high – temperature resistance and super – strong corrosion resistance, it is used in aerospace (turbine blades, combustion chambers, exhaust pipes, etc.), chemical reaction devices, gas turbine components, marine engineering (ship propellers, submarine communications, cable sheaths), nuclear reactor components, and high – pressure containers in petrochemicals.
• ​Incoloy 825 Nickel – based alloy​​: It is widely used in pipelines, storage tanks, and heat exchangers in the chemical and petrochemical industries in strong – acid environments such as sulfuric acid, phosphoric acid, and hydrochloric acid. It is also used in hot – rolling acid – pickling line equipment, chloride – solution pump bodies, gas desulfurization towers, and chemical processing production devices. It is also used in the annealing system of nuclear power plants, seawater valves, and marine environment equipment.