All about Monel®, Part One: Does Monel® Corrode/Rust?

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One of the metals that we receive many inquiries about is Monel®, and we’d like to take this opportunity to begin the first of a three-part series, providing information on Monel and answering the three most frequent questions we hear.As leading distributors of high-quality metals for over two decades, we have many new clients who come to us to supply their varying metal needs. We also have many customers coming to us with questions about the different metals, their properties, and their applications.

The nature of Monel as a Nickel-Copper alloy (we will delve into that more in another post) is such that it is highly resistant to corrosion and acids. In fact, some Monel, depending on the alloys in it, can withstand fire in pure oxygen.Question # 1: Does Monel® Corrode/Rust?

Its corrosion resistance makes it stand up to a wide range of environments and conditions, including, but not limited to, sea salt/water, rapidly flowing water, pure water, and nonoxidizing mineral acids, salts, and alkalis. It is exceptionally resistant to hydrochloric and hydrofluoric acids when de-aerated (removed from air & gas), and is known for its excellent resistance to chloride ion stress corrosion cracking. In certain circumstances, Monel is more resistant than both nickel and copper. It is also known for its temperature resistance, with good mechanical properties from subzero temperatures up to around 1020°F/550°C, depending on grade.

Because of Monel’s exceptional corrosion resistance, it is often the metal of choice for industries such as chemical processing, petro-chem, and high pressure/temperature steam applications. For a range of marine applications, Monel is ideal. These include ocean-based oil rigs, valves, piping systems, and many more applications that experience exposure to sea water.

Monel is also used extensively in aerospace applications, due to its resistance to extreme temperatures. It’s been used in many aspects of aircraft and rocket construction, including the exteriors of X-15s. Below is a chart of the various grades of Monel.

Name UNS ASTM/AISI steel type
Monel 400 N04400 B 127, B, 164
Monel 401 N04401
Monel 404 N04404 B 164
Monel K-500 N05500 B 865
Monel R-405 N04405

Of course these are just some examples of the many applications to benefit from the corrosion-resistance (and other advantages) of Monel. If you have any specific questions, feel free to contact us, and stay tuned for the remaining two posts in this three-part series on Monel.