What Is Stainless Steel Pipe?

Stainless steel pipe is produced in two main types: welded and seamless. Stainless steel pipe is used across a wide range of industries, most notably food, chemicals, textiles, automotive, construction, and general manufacturing.

Welded Stainless Steel Pipe

Welded pipe is made from stainless steel plate that is slit to width, cold-formed into a round section, and then joined with a longitudinal weld. Welded stainless pipe is produced to different standards depending on its intended application. Pipe for decorative use is produced to EN 10296-2 using high-frequency (HF) welding, while pipe for industrial applications and pressurized fluid systems is produced to EN 10217-7 using TIG or laser welding.

Seamless Stainless Steel Pipe

Seamless stainless pipe, by contrast, is hot-formed from billets heated to forging temperature.

Depending on the application, stainless pipe is supplied with a pickled, bead-blasted, brushed, or polished surface finish. Stainless steel piping is used in plumbing systems and, above all, in industrial plants to convey liquids, gases, and other fluids from one point to another. Whether welded or seamless pipe is the right choice for a given line depends on the type of product being conveyed, its pressure, and its temperature. AISI 304 stainless pipe is the standard choice for most piping systems, while AISI 316, AISI 321, AISI 309, AISI 310, and duplex stainless pipe are selected according to the properties of the product carried in the line.

Corrosion of Stainless Steel Pipe

Stainless steel pipe resists corrosion thanks to the formation of metal oxides in its structure, which create an invisible passive protective layer on the surface. This passive layer can be damaged, however, by water with a high chloride content or by chlorides left on installation lines and pipe surfaces, especially when the surfaces are cleaned with oxidizing agents, and corrosion then sets in. High chloride levels in water are a common cause of corrosion in piping. Another leading cause of corrosion in stainless pipe is poor welding and installation practice. Selecting stainless pipe in a grade suited to the application is one of the most effective precautions against the risk of corrosion.