A duplex pipe is a type of stainless steel pipe made from duplex stainless steel, which has a mixed microstructure of austenite and ferrite in roughly equal proportions. This unique combination gives duplex stainless steel superior strength and excellent resistance to corrosion, stress corrosion cracking, and pitting compared to regular stainless steel. Duplex pipes are commonly used in industries such as oil and gas, petrochemicals, and chemical processing, where high performance in harsh environments is essential. Additionally, they offer good weldability and are suitable for use in a range of temperatures.

The choice between seamless and ERW (Electric Resistance Welded) pipes depends on the application and specific requirements. Seamless pipes are generally considered stronger and more reliable under high pressure, making them ideal for critical applications in the oil and gas industry, power plants, and high-pressure environments. They are manufactured without a weld seam, reducing the risk of leaks and failures. On the other hand, ERW pipes are more cost-effective and have a smooth internal surface, making them suitable for applications like water pipelines, structural purposes, and low- to medium-pressure systems. ERW pipes are often preferred when high precision and uniformity are needed, but they may not be as strong as seamless pipes under extreme conditions. Overall, the choice depends on the operating conditions, pressure requirements, and budget considerations.

Duplex 2205 pipe is available in a range of sizes to suit various applications. The sizes typically range from small diameter pipes to large ones, with common outer diameters starting from 1/8 inch (3.2 mm) up to 24 inches (610 mm) or even larger in some cases. The wall thickness of Duplex 2205 pipes can also vary based on specific requirements and can be specified as Schedule 5, Schedule 10, Schedule 40, Schedule 80, and beyond. The exact size and schedule of Duplex 2205 pipe depend on the application and the standards specified, such as ASTM, ASME, or API requirements.

Duplex 2205 and 316 stainless steel (SS) differ primarily in their chemical composition and mechanical properties. Duplex 2205 is a duplex stainless steel that has a balanced microstructure of austenite and ferrite, giving it higher strength and significantly better resistance to stress corrosion cracking and pitting in chloride environments compared to 316 SS, which is an austenitic stainless steel. 316 SS, which contains molybdenum, offers good general corrosion resistance and is easier to form and weld, making it suitable for a wide range of less demanding applications. In contrast, Duplex 2205 is preferred for more challenging environments, such as in the oil and gas industry, chemical processing, and marine applications, due to its superior durability and resistance.