Alloy 400 is a single-phase solid-solution nickel copper alloy with excellent corrosion resistance to a wide range of media.
Alloy 400 is characterized by:
- Corrosion resistance in a wide range of marine and chemical environments
- Freedom from chloride induced stress-corrosion cracking
- Good mechanical properties from sub-zero temperatures up to approximately 550°C (1020°F)
- Good workability and weldability
What is Nickel Alloy 400
Nickel Alloy 400 is a highly versatile material with a high degree of resistance to corrosion. Because its composition is primarily Nickel and Copper, its properties combine the best of both elements. Copper, a noble metal, is highly resistant to both corrosion and oxidation. Nickel’s passivation property allows for corrosion-resistance to be bolstered through that process.
Nickel Alloy 400 uses the strengths of both its primary components to create a level of durability against decay that stands up under a diverse array of environmental and elemental factors of degradation.
Characteristics of Nickel Alloy 400
To be classified as Nickel Alloy 400, the alloy must consist of between 63-70% Nickel and 28-34% Copper. However, trace amounts of other elements such as Carbon (up to 0.3%), Silicon (up to 0.5%), Manganese (up to 2.0%), Sulfur (up to 0.24%), Iron (up to 2.5%), and Aluminum (up to0 .5%) may be present.
Nickel Alloy 400 is appropriate for deployment under harsh marine conditions, as well as a number of corrosive chemical environments. It is not subject to cracking from stress-corrosion due to the presence of chlorides.
Alloy 400 responds well in a wide range of ambient temperatures, ranging from sub-zero, all the way up to 1,020°F (550°C). And it is suitable for use in pressure vessels, per ASME Boiler and Pressure Vessel Code, with wall temperatures ranging up to 900°F (480°C).
Nickel Alloy 400 is easy to work with, and welds effectively. It meets compliance requirements under UNS: NO400, W. NR: 2.436, AMS: 4554, ASME: SB 127, ASTM: B 127, and federal/military: QQ-N-281 standards.
Nickel Alloy 400 Plate Applications
As mentioned earlier, Nickel Alloy 400 works well in marine environments. Specifically, successful deployment has been proven in offshore structures as splash-zone shielding, as well as such facilities as seawater desalination plants.
It has been shown to be effective in the bodies of evaporator units as well as brine heaters in these facilities. Propeller shafts and pump shafts that maintain constant contact with seawater can live extended useful lives when plated with Nickel Alloy 400.
Alloy 400 has been the standard material used in salt plants for a long time now. It is one of only a few materials of metallic composition that can be used in applications where direct contact with fluorine is part of the process. This goes for several fluorine derivatives, including hydrofluoric acid, and hydrogen fluorine.
Power plants designers have also been known to choose Nickel Alloy 400 as tubing material for steam-generators and feed-water supply lines. It is also widely used in high-temperature industrial heat exchangers.
The high level of corrosion-resistance in Nickel Alloy 400 makes it a good choice for highly acidic environments. Hydrofluoric and Sulfuric acid alkylation plants are such examples.
Crude oil distillation columns require a high level of corrosion-resistance, and Nickel Alloy 400 is able to meet this need. In the process of manufacturing chlorinated hydrocarbons, pumps and valves constructed using this material as necessary will create favorable results as well.
Other specialty applications requiring high corrosion-resistance, where Nickel Alloy 400 has been effective, include Monoethanolamine (MEA) reboiler tubing, and nuclear fuel production plants separating uranium and isotopes.
Corrosion-resistance properties of Alloy 400
In addition to the previously mentioned applicability for use in contact with fluorine and fluorine derivatives, Nickel Alloy 400 also tests well in resistance to a number of caustic alkalis.
Alloy 400 is proven highly effective in applications where seawater corrosion is a particular concern, due to the high level of resistance to cavitation-based corrosion. It is shown to be superior to Copper-based alloys in particular in marine environments.
If dilute solutions of mineral acids, such as hydrochloric and sulfuric acids, are air-free, Nickel Alloy 400 can be placed in direct contact with them. If they are not air-free, levels of corrosion can be higher. But depending on the application, Alloy 400 may still be an appropriate choice of material.
Weaknesses of Nickel Alloy 400
Nickel Alloy 400 does not contain chromium. Therefore, it may experience a decrease in corrosion-resistance capabilities under some oxidizing conditions.
Despite its near imperviousness to chloride-ion stress cracking, this alloy can experience cracking when mercury or hydrofluoric acid vapors are present, such as in the process of HF etching. However, the potential for cracking under these conditions can be remedied through the application of a stress-relieving heat-treatment.
Nickel Alloy 400 is an extremely versatile material with high levels of durability and longevity. It has been found to be useful in a number of sectors where resistance to high-temperatures and corrosion are critical to performance. This includes not only many niche areas, but also very commonplace environments as well.
From common seawater, to fluorine and its derivatives, to nuclear fuel, Nickel Alloy 400 is increasingly bringing value throughout the world where strong, durable, and long-lasting metallic materials are in demand.
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