Applications of INCONEL Alloy 22

Extremely resistant to aqueous and general corrosion, crevice corrosion, intergranular attack, pitting, and stress corrosion cracking, INCONEL alloy 22 is tough and versatile even at elevated temperatures. Nickel-based and with 22% chromium, alloy 22 is fully austenitic. This means that it’s non-magnetic and does not harden in response to heat treatment. Nickel also helps to protect the alloy against corrosion by halides, such as chlorides and fluorides, when subject to extreme heat.

In addition to nickel and chromium, alloy 22 also contains 14% molybdenum and 3% tungsten. These two metals make the alloy resistant to wet reducing media, such as ferric and cupric salts and nitric acid. Combined with chromium’s resistance to wet oxidising media – such as ferric and cupric salts and nitric acid – this makes INCONEL alloy 22 particularly suitable for use in highly corrosive environments where safety is a crucial concern.

In this blog post, we’ll explore some of the most common industrial applications of alloy 22, including pollution control (flue gas desulphurisation), waste disposal, power generation, pulp & paper processing, marine applications, and chemical and petrochemical processing.

Pollution control, waste disposal and power generation

Sulphur dioxide emissions are strictly regulated in many countries due to the pollution created by fossil-fuel combustion. This is a particular concern for coal-fired power stations. Flue gas desulphurisation uses chemical reactions to remove sulphur dioxide from the exhaust flue gases generated by the combustion process. This is highly effective in limiting the amount of SO2 emitted.

Various technologies have been developed, of which the most common are wet scrubbing using seawater or an alkaline sorbent slurry, often lime or limestone; and dry scrubbing using the same alkaline sorbent. Whichever method is chosen, flue gas desulphurisation involves using highly corrosive materials. Alloy 22 is therefore a natural choice when it comes to manufacturing the equipment.

Alloy 22 is an excellent material for containers built to contain corrosive waste. It’s also used as a protective overlay on boiler tubes and waterwalls in coal-fired power plants, due to its resistance to extreme heat and corrosion. This is particularly important because the sulphur dioxide, sulphur trioxide and water vapour produced by fossil-fuel combustion condense at high temperatures to produce sulphuric and sulphurous acids.

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This alloy is approved under the ASME Boiler and Pressure Vessel Code Section VIII, Division 1, for building pressure vessels and components for use at up to 677°C.

Pulp and paper processing

Pulp and paper processing is another sector in which metal components have to function in a highly corrosive environment. Regardless of technology, any pulp or paper mill uses harsh media such as bleaches, acids and salts, and some stages of the production process also involve elevated temperatures. A highly resistant alloy is therefore required to prevent components from deforming, pitting, cracking or corroding for as long as possible. INCONEL alloy 22 is a popular choice, due to its resistance to all kinds of corrosive media at extreme heat.

Marine applications

Alloy 22’s aqueous corrosion properties are its superpower when it comes to using metal components in a marine environment. Due to its high saline content, seawater corrodes metal five times faster than fresh water. Because components used in shipbuilding, offshore and other marine applications will be exposed to seawater – possibly even immersed in it – throughout their operative life, it’s extremely important to choose a material that will resist damage for as long as possible. Component failure increases maintenance outlay, compromises safety, and shortens the life of vessels and installations. The consequences of aqueous corrosion can be rapid and severe.

Nickel alloys in general are standard for use in marine and offshore applications. INCONEL alloy 22 in particular is regarded as an outstanding choice by marine engineers for its exceptional ability to resist attack by seawater, in both stagnant and flowing conditions. Piping and heat exchanger tubing are just two of its uses in the offshore oil and gas industry.

Chemical and petrochemical processing

Because alloy 22 is extremely resistant to attack by all kinds of corrosive media, it’s highly valued in the chemical and petrochemical processing sectors. A pipe or container made with alloy 22 is capable of safely containing or channelling harsh chemical substances while remaining intact and safe from corrosion, pitting and cracking in a hot and/or corrosive environment. As an austenitic alloy with less than 3% iron content, alloy 22 is also resistant to creep – the deformation produced by repeated mechanical stress at high temperatures – as well as embrittlement.

The benefits of INCONEL alloy 22 in such an environment are obvious. It offers longer operative life, easier cleaning due to the lack of pitting and cracking, less maintenance and better cost-efficiency. Using alloy 22 for the manufacture of containers, components and tubing also provides considerable protection against leaking, contamination and other potentially dangerous outcomes. In such a high-stakes, high-pressure field of application, alloy 22’s exceptional corrosion qualities and ability to endure high temperatures make it stand out, even compared to other nickel alloys.

Similar alloys

If your project requires a nickel alloy with excellent corrosion resistance, one alternative to Alloy 22 is INCONEL alloy 625. This versatile alloy, which includes niobium for added strength without heat treatment, is also popular across many of the same industry sectors – marine, power, pulp & paper processing – as well as in the aerospace, oil extraction & refining, and automobile sectors.

Another possibility is INCOLOY alloy 825. Also popular with marine engineers, this was the first nickel alloy to incorporate molybdenum, and it’s still considered one of the best. Like alloy 22, it’s distinguished by its exceptional corrosion resistance across a range of media, although it works best up to moderately high temperatures.

At Corrotherm, we supply a number of corrosion-resistant nickel alloys. To see the full range, visit our Grades section. We’re happy to help you find the material that best suits the precise requirements of your project, budget and aims. If you would like to discuss a particular alloy or choose the best one for your needs, contact a member of our sales team.

Topics: Corrotherm News

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