Is C22 magnetic?
INCONEL Alloy C22 is extremely resistant to aqueous corrosion and general corrosion, crevice corrosion, intergranular corrosion, pitting and stress corrosion cracking, and is tough and versatile even at high temperatures. C22 alloy is nickel-based, contains 22% chromium and is fully austenitic. This means it is nonmagnetic and does not harden with heat treatment. Nickel also helps protect the alloy from corrosion by halides, such as chlorides and fluorides, at extremely high temperatures.
In addition to nickel and chromium, C22 alloy contains 14% molybdenum and 3% tungsten. These two metals make the alloy resistant to wet reducing media, such as iron and copper salts, and nitric acid. This, combined with chromium's resistance to wet oxidizing media, such as iron and copper salts, and nitric acid, makes INCONEL Alloy C22 particularly suitable for use in highly corrosive environments where safety is paramount.
In this newsletter, we will explore some of the most common industrial applications for Alloy C22, including pollution control (flue gas desulfurization), waste treatment, power generation, pulp and paper processing, marine applications, and chemical and petrochemical processing.
Pollution Control, Waste Treatment, and Power Generation
Many countries strictly regulate sulfur dioxide emissions due to pollution caused by the burning of fossil fuels. This is particularly concerning for coal-fired power stations. Flue gas desulfurization uses a chemical reaction to remove sulfur dioxide from the exhaust gases produced by the combustion process. This is very effective in limiting sulfur dioxide emissions.
Various technologies have been developed, the most common of which are wet scrubbing using seawater or a slurry of an alkaline sorbent (usually lime or limestone); and dry scrubbing using the same alkaline sorbent. Regardless of the method chosen, flue gas desulfurization involves the use of highly corrosive materials. Therefore, when manufacturing equipment, Alloy C22 is a natural choice.
Alloy C22 is an excellent material for containers used to hold corrosive wastes. It is also used as a protective layer for boiler tubes and water walls in coal-fired power plants due to its high temperature and corrosion resistance. This is particularly important because sulfur dioxide, sulfur trioxide, and water vapor produced by the combustion of fossil fuels condense at high temperatures to produce sulfuric and sulfurous acids.
The alloy is approved for the construction of pressure vessels and components up to 677°C according to the ASME Boiler and Pressure Vessel Code, Section VIII, Division 1.
Pulp and Paper Processing
Pulp and paper processing is another industry where metal components must work in a highly corrosive environment. Regardless of the technology used, any pulp or paper mill uses corrosive media such as bleach, acids, and salts, and some stages of the production process involve high temperatures. Therefore, a highly resistant alloy is needed to prevent components from deforming, pitting, cracking, or corroding for as long as possible. INCONEL Alloy C22 is a popular choice because of its resistance to a variety of corrosive media under extremely hot conditions.
Marine Applications
The water corrosion resistance of Alloy C22 is its superb ability to use metal components in marine environments. Due to its high salt content, seawater corrodes metals five times faster than freshwater. Since components used in shipbuilding, offshore, and other marine applications will be exposed to seawater throughout their service life-and possibly even immersed in it-it is important to choose a material that will resist damage for as long as possible. Component failure increases maintenance expenses, compromises safety, and shortens the life of vessels and equipment. The consequences of water corrosion can be rapid and severe.
Nickel alloys are often the standard for marine and offshore applications. INCONEL Alloy C22, in particular, is considered an excellent choice by marine engineers because of its outstanding resistance to seawater erosion in both stagnant and flowing conditions. Piping and heat exchanger tubing are just two of its uses in the offshore oil and gas industry.
