Choosing the Right Corrosion-Resistant Alloys for Your Projects

When it comes to corrosion-resistant alloys (CRAs), there is a wide variety to choose from. Austenitic stainless steel, aluminum 6— series, and nickel-copper alloys are a few types of corrosion-resistant alloys frequently used by San Francisco Bay Area manufacturers, fabricators, and machine shops. CRAs are usually categorized according to resistance levels related to exposure in particular environments. For the moment, let’s focus on one of the most commonly used types of corrosion-resistant alloys, Monel, which is a nickel-copper alloy.

What is Monel?

Monel, trademarked by Special Metals, describes a group of nickel-copper and copper-nickel alloys. The nickel-copper alloys contain anywhere from 52-67% nickel and 28-33% copper, combined with small amounts of carbon, iron, manganese, and silicon. The addition of these and other elements determines the characteristics of the different alloys. The alloys are stronger than pure nickel and are exceptionally corrosion-resistant.

Monel alloys retain their strength at elevated temperatures, allowing them to maintain their shape at high-atmosphere flight speeds. That characteristic also makes Monel alloys ideal for boiler feedwater heaters and other heat exchangers. 

These alloys are also suitable for oil production and refining applications because of their excellent corrosion resistance to hydrofluoric, sulfuric, and hydrochloric acids and high-temperature tolerance. They also excel in marine applications as the preferred metal for propeller and pump shafts, keel bolts, rivets, and seawater valves—where contact with aluminum is likely to induce corrosion. 

Types of Monel Nickel-Copper Alloys

The various types of Monel nickel-copper alloys are listed below, but not all Monel alloys are nickel-copper. Monel 401 and 450 are copper-nickel alloys (the percentage of copper is greater than the percentage of nickel). Monel 400 and K-500 are two of the Monel alloys used widely by San Francisco Bay Area machine shops and fabricators.

• Monel 400 contains the same proportions of nickel and copper found naturally in certain nickel ore mines. The composition ranges from a minimum of 63% nickel and anywhere from 28-34% copper.
• Monel 404 is formulated specifically for low temperatures. The composition is 50-57% nickel and less than or equal to 45.5% copper.
• Monel R-405 includes a small amount of sulfur to produce sulfide inclusions that act as chip breakers during machining. This property makes it ideal for fasteners, screw-machine products, and valve parts. The composition ranges from a minimum of 63% nickel and anywhere from 28-34% copper.
• Monel K-500 offers the same corrosion resistance as Monel 400, with the advantage of greater strength and hardness provided by adding aluminum and titanium to the nickel-copper base. Applications include oil well tools, as well as pump and marine propeller shafts. The composition ranges from a minimum of 63% nickel and anywhere from 27-33% copper.
• Monel 502 offers good creep and oxidation resistance and has machining characteristics similar to austenitic stainless steel. The composition is 63-70% nickel, 2.5-3.5% aluminum, 2% iron, and 1.5% manganese, with silicon, carbon, sulfur, and copper making up the remainder. 

Monel corrosion-resistant alloys command a higher price than many common metals. Depending on the type and form, these corrosion-resistant alloys, purchased directly from the mill, may cost up to 20 times more than carbon steel, for example.

Corrosion-Resistant Alloys at Highly Competitive Prices

Many machine shops are discovering cheaper options for purchasing corrosion-resistant alloys. San Francisco Bay Area industrial metal recyclers buy usable Monel alloy remnants from manufacturers who source Monel alloys directly from the mills. These remnants are too small for the manufacturers to use in their ongoing production processes but are ample size for the production of smaller components or use in smaller production runs. 

In many ways, these usable remnants are the ultimate way to recycle. There’s no need for usable Monel remnants to be sent back to the mill for reprocessing when they’re still suitable for certain production processes. The best metal suppliers carry a wide selection of recycled Monel remnants and use x-ray fluorescent scanners such as the Thermo-Fisher XRF to verify the composition of the alloys before selling. Monel remnants at a fraction of the cost of new are a win for both the environment and the machine shops purchasing them.

Monel and Other Corrosion-Resistant Alloys Available Locally 

Industrial Metal Service specializes in metal recycling and supplying an extensive range of high-quality, usable metal remnants, including corrosion-resistant alloys, aluminum, stainless steel, and titanium to San Francisco Bay Area manufacturers, fabricators, welders, and machine shops. We offer delivery anywhere within the Bay Area and frequently ship metals nationwide to shops that don’t have the benefit of a local metal supplier.