Monel has been around for more than a century, and though it’s not as ubiquitous as it used to be, it is still a valuable alloy in several heavy duty applications. Monel is a nickel-copper alloy that also includes small amounts of iron, manganese and, in some varieties, silicon and aluminum. It is an expensive alloy to fabricate and shape, as it hardens very quickly prior to working. As such, Monel is only used when other, easier to fabricate alloys cannot be used in a particular application. These production and economic concerns make it a primary target for recycling, and commercial scrap metal experts prioritize it.
Although Monel has to be manufactured using slow feeding rates, once it is fabricated, it is a tough, useful alloy. Some varieties of Monel offer better strength than steel and stainless steel, but that’s not what makes it a notable alloy, as plenty of alloys can claim that. What does make Monel so impressive is its corrosion and temperature resistance. It offers fantastic durability against many kinds of acids and is a strong choice in any corrosive environments, including environments exposed to seawater.
Monel can also withstand extremely low temperatures without losing its desirable mechanical properties. Normally, when ferrous alloys are cooled below subzero temperatures, they eventually transition from a ductile to a brittle state, which makes them highly susceptible to impact forces, even though they possess improved strength. Monel also increases in strength at low temperatures, but without the side effect of becoming brittle. This unique quirk of Monel holds true even when the alloy is cooled down to the temperature of liquid hydrogen.
Where Monel Can Be Found
Again, Monel is not used as extensively as it once was, but it can still be scrapped in large amounts if a metal recovery expert knows where to look. Some of the most common sources of Monel include, or once included:
- Marine applications – Perhaps the one area where Monel is still in heavy use is in boating, as it offers excellent resistance to seawater corrosion. However, in the presence of electrolytes, like sodium, it will enter galvanic corrosion with other metals. For this reason, it needs to be insulated from other metals, like steel, on the vessel. Still, it is an attractive option for the production of pump and piping systems, strainer baskets, valves and wiring. It is a popular choice for keel bolts and propeller shafts, and is relied on to store fuel and water. Finally, it is often incorporated into anchoring systems, and particularly seize shackles. Given the widespread use of Monel in marine applications, metal recovery experts can uncover a great deal of it following shipbreaking operations.
- Petroleum refining – Monel is the preferred metal for alkylation units in the oil and gas industry. During alkylation, isobutene is converted into gasoline components. This process requires the presence of a strong acid, such as hydrofluoric acid. Few materials are capable of withstanding exposure to hydrofluoric acid, but Monel is among them. In fact, Monel is considered by many to be the best at handling attacks by hydrofluoric acid. As such, it is a common metal used in alkylation containers.
- Aerospace construction – Back in the 1960s, Monel was utilized extensively in aircraft manufacturing. It was built into the skin and frame of a great variety of rocket planes, as it maintains its strength and shape at high speeds and temperatures. While scrappers may find the occasional decommissioned airplane from the 60s, and a treasure trove of Monel as a result, most scrappers look for Monel wiring in modern aircraft, as it is still needed to maintain connections with fasteners.
- Musical instruments – Monel is a standard alloy in use with some music instruments. Specifically, it is utilized in bass guitar strings and in various brass instruments, including trumpets, French horns and tubas. In brass instruments, it is most often built into the valve pistons, where it produces a strong seal. Valve pistons can be replaced independently of the instrument, and they are often recycled for their Monel and brass content.
Monel is not easy to find, and it’s not easy to process once found. It has to be ripped out of aircraft, torn out of alkylation tanks, salvaged from decommissioned vessels or found piecemeal in music instruments or appliances. That amount of work is not something that the typical scrapper hobbyist is capable of performing. For this reason, it’s work that is best left to scrappers experienced in working with industrial clients. They have the manpower and equipment needed to process tons of material, and they offer the best chance at recycling as much Monel as possible.