Monel belongs to the family of nickel-based alloys. It chiefly consists of nickel and copper while silicon and carbon are present in a smaller amount. The contents of this alloy when fabricated using machining, welding and hot-cold working are known to offer better strength. Monel 400 is also known as high resistance alloy that exhibits corrosion resistance against seawater. It is an expensive alloy hence you won’t find many applications the industrial field. Its resistance to a number of corrosive conditions leads to its wide use in the marine application field. Alloy 400 is a solid solution alloy which can be hardened only by cold working. This nickel alloy also exhibits good weldability.

Characteristics of Monel 400

• At high temperatures, it is resistant to steam and seawater
• Monel 400 is highly resistant to rapidly flowing seawater or brackish water
• It also exhibits excellent resistance to stress corrosion cracking in freshwater
• The alloy is predominantly resistant to hydrofluoric and hydrochloric acids when de-aerated
• The alloy offers some kind of resistance to sulfuric and hydrochloric acids at modest temperatures and concentrations
• It is known to have excellent resistance to a neutral and alkaline salt

Corrosion Resistance

The alloy Monel 400 wire is essentially immune to chloride-ion stress corrosion cracking in some of the typical environments. Normally, its corrosion resistance is quite good in reducing environments but equally poor in oxidizing conditions. It is practically of no use in oxidizing acids, like nitric acid and nitrous. But it shows good resistance to most salts, alkalis, waters, organic substances food products and atmospheric conditions both at normal and high temperatures.

At subzero temperatures, Monel 400 exhibits great mechanical properties and it can be used in temperatures up to 1000° F. Its melting point is 2370-2460° F.

Its behavior in gas and steam

Monel 400 can be used at moderately high temperatures and corrosive environments like it is used in oil gasification plants.

It even plays an important role in the oil and gas industry in the production of refining and extraction of oil. It is used for both onshore and offshore extractions and it is engaged for the manufacturing of Monel 400 valves, pumps and also process control equipment. Since it is made out of copper and nickel content, together they offer features like good tensile strength and corrosion resistance. It is preferred to be used in the oil and gas industry because of its high strength and excellent corrosion resistance.

Above approximately 700° F Monel 400 alloy is attacked in sulfur-bearing gases and at temperatures of over approximately 500° F molten sulfur attacks the alloy. The corrosion resistance of Monel 400 is about the same as nickel but has higher working pressure and temperatures. Its cost is also lower due to its superior ability to be machined.

The combination of the creep strength and moderate oxidation resistance extends its application in the steam generator tubing and some other components operating at temperatures up to 550 °C in a conventional fossil-fuel power plant.