It’s no surprise that stainless steel is gaining popularity in the chemical and petrochemical industries. Its ability to resist attack by highly corrosive substances, along with its excellent mechanical properties, are key factors in its continued high demand. As industrial processes evolve and change, and new challenges arise, exciting new applications for stainless steel are being explored to take advantage of the material’s key benefits.

The main difference between stainless steel and carbon steel is the chromium content. Chromium forms a thin layer of chromium oxide on the surface, which blocks corrosion from penetrating the metal. Even if the oxide layer is damaged, it quickly repairs itself as new chromium is exposed and oxidized.

Another advantage of stainless steel is that it is recyclable. Unlike carbon steel, which can corrode or can become contaminated by paint or plate surfaces, stainless steel is 100% recyclable. In fact, most stainless steel items are said to contain up to 60% recycled material.

The conditions under which stainless steel is used in petrochemical and chemical plants are critical. Processed fluids and extremely high temperatures can be particularly corrosive during operation; the presence of chlorides or environments where induced cracking occurs are key challenges.

The chemical and petrochemical industries face a unique set of challenges, including cryogenic applications, high temperatures, highly corrosive environments, high pressure processing, and purity of the final product.

Oil refining uses increasingly complex processes, which has led to the need for advances in chemical and mechanical engineering to increase yields and improve operational reliability. Reducing or eliminating potential contaminants in the process and product is a top priority. The industry is also placing an increasing emphasis on materials engineering, with a growing interest in high alloy corrosion resistant steels, especially stainless steels, due to their ability to handle a wide range of crude oils.

The market for stainless steel tanks, pipes, pumps, and valves is huge. Special grades of stainless steel have also been developed with increased corrosion resistance at a wide range of temperatures to maximize performance. Such products are often used in desalination plants, wastewater treatment plants, and offshore oil rigs.

There are five types of stainless steel:

Ferritic: These steels are based on chromium and contain small amounts of carbon (usually less than 0.10%). They are used in thin sections and have a range of applications that do not require welding. They cannot be hardened by heat treatment. Ferritic steels are selected for their resistance to stress corrosion cracking.

Austenitic: This is the most common type and has nickel, manganese and nitrogen added to its microstructure to improve weldability and formability. Corrosion resistance is enhanced by the addition of chromium and molybdenum.

Martensitic: Similar to ferritic steels, but with a higher carbon content, which means they can be hardened and tempered. Martensitic steels are used if high strength and moderate corrosion resistance are required, and are usually produced in long product form rather than sheet or plate.

Duplex: These have a microstructure of 50% ferrite and 50% austenite, offering higher strength and resistance to stress corrosion cracking. Super duplex steels offer even higher strength and corrosion resistance, weldability and moderate formability. They also have the potential to reduce weight.

Precipitation Hardened (PH): These super-strong steels have elements such as copper, niobium and aluminum added to them, and form a strong particle matrix during heat treatment. These steels can be machined into complex shapes with minimal distortion.