Monel Alloys for Down-Hole and Marine Applications

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Monel alloy, a combination of nickel and copper, is used for a wide range of purposes including offshore and marine applications. With offshore oil and gas production progressively moving into deeper parts of the ocean, there is a demand for strong, corrosion resistant materials that can withstand the extreme conditions of underwater environments.

Monel alloys have excellent corrosion resistance, good ductility, and can withstand exposure to acids and alkalis, making them a prime material for offshore drilling and marine applications. Monel demonstrates a superior resistance to elevated temperatures and stress cracking under pressure. Though there are many types of Monel, 400, 404, and K-500 are best suited for these applications. Monel is used in oil and gas exploration where components will be exposed to “down hole” environments at high temperature along with high hydrogen sulfide concentrations. Monel is used in these “sour wells” as the conditions prove rapidly degrading to stainless steels. Monel can come in a variety of forms and grades at different price points. Companies can purchase Monel in either hot-or cold-rolled sheets, strips, plates, tubes, rods, and bars.

As a puritan alloy, Monel 400 offers many advantages including excellent corrosion resistance to seawater and steam, resistance to sulfuric and hydrofluoric acids, good weldability, and moderate to high strength. However, this alloy does have its limits as it cannot be hot worked. On average, Monel 400 contains at least 63 percent nickel, 28 to 34 percent copper, and no more than 2 percent of manganese. It also has trace amounts of silicon, iron, carbon, and sulfur. The nickel contributes to the strength and corrosion resistance while the copper increases ductility and electrical conductivity. Recently, the presence of hydrofluoric acid in seawater has been steadily increasing, which has created a need for materials that can withstand the effect of acidic corrosion. Underwater volcanoes also release hydrofluoric acid during eruptions. Monel 400 is a good fit in waters with high concentrations of hydrofluoric acid. Other marine applications for this alloy include piping systems, valves, trolling wire, and strainer baskets. It is also used in the production of piping and cladding for oil refinery columns and in the legs and risers of offshore platforms.

Monel 404 is different from other alloys because it can provide an incredibly low Curie temperature. It also has low permeability, superior brazing characteristics, can be machined and formed using conventional techniques, and has good weldability. It can be cold rolled to various tempers; however, it cannot be hot worked or forged. Monel 404 contains less nickel than other types of Monel alloys, with ranges between 52-57%. The remainder of its chemical composition is between 42-47% copper, along with small percentages of manganese, iron, silicon, and aluminum. Generally, 404 is used in the production of electronic components, such as ceramic-metal seals and transistor parts but, it’s also used in the construction of boat parts and marine fixtures, such as water heaters, gas tanks, and pumps.

Monel K-500 is similar to Monel 400; however, K-500 is chemically enhanced to provide higher corrosion resistance, tensile strength, and hardness. Monel K-500 can be hot worked between 1600–2100°F. Titanium and aluminum contribute to Monel K-500’s high strength. It usually has at least 63% nickel and 27-33% copper. The rest of the chemical composition is made up of titanium, iron, aluminum, phosphorous, sulfur, silicon, manganese, and carbon. Monel K-500 has excellent mechanical properties in sub-temperatures. Due to a lack of sunlight, deep sea water can be very cold, which makes this alloy excellent for parts that will reach depths of two hundred meters or greater. Monel K-500 is used for creating both marine and submarine parts, such as blades, pumping shafts, and seawater valves. It is often used in the production of centrifugal pumps due to its high strength and excellent corrosion resistance. As a non-magnetic alloy, Monel K-500 is also used for anchor cable on minesweepers.

When it comes to machining, there are benefits to using shaped wire. Unlike other forms of metal, shaped wire can contain prerolled features, which allows manufacturers to skip certain steps of the stamping process to achieve a desired shape, saving production time and requiring less specialized machinery. Rolling shaped wire closer to near-net shape can reduce waste and optimize costs on material. Other benefits include tight dimensional tolerance and adaptability to roll into complex shapes. Shaped wire is often used in the production of gaskets and seals, wedge wire, engines, and heat exchangers.

Monel 400 tends to be the most expensive alloy to source. Compared to carbon steel piping, Monel is about three times the price. On average, it costs about four times the cost of pure nickel, and six to eight times more than stainless steel. As the demand for Monel increases, the price will likely increase too. Compared to other metals, Monel can be cost prohibitive. Because of this, it is used only in applications where other materials would corrode. Galvanic corrosion is an example of this. It occurs when two different metals make contact with one another and are simultaneously exposed to a corrosive electrolyte. The exposure causes one of the two metals to corrode more quickly than if it were on its own. As a result, Monel 400 and Monel K-500 can experience galvanic corrosion when in contact with other kinds of metal.

To summarize, Monel is a versatile alloy used across many industries, from marine applications to electronics. Regardless of its purpose, sourcing high-quality Monel is essential in the construction of long-lasting parts. For more than one hundred years, Ulbrich Stainless Steel has been a leader in the production of specialty metals and alloys. Companies can rely on Ulbrich for their high-quality materials and expert knowledge in the field of metallurgy. To find out which type of Monel is best suited for your next project, contact Ulbrich Stainless Steel.