Types of Corrosion Resistant Metals and Their Uses

The importance of non-corrosive metals

Non-corrosive metals are used for varying roles within the automotive, marine, electrical and architectural industries. It is their ability to endure deterioration and chemical breakdown which makes them such a valuable commodity. Metals such as these can support the longevity of a structure, its strength and load-bearing ability and aid in the prevention of cross contamination.

Certain metals and metal alloys allow stronger corrosion resistance to others. For each metal, there are a multitude of different grades which demonstrate the varying levels of corrosion resistance. Metals are tested and should meet specific standards, withstanding stresses and perform even when exposed to aggressive chemicals. When using metals for structural purposes, materials should be corrosion resistant, strong, lightweight and easily malleable to support with the installation process.

What is corrosion?

Metals can corrode in a multitude of ways, depending upon their environment or design. Typically, corrosion occurs due to exposure to water, electricity, heat and aggressive chemicals. The three most common types of metal corrosion are: general attack corrosion, localised corrosion and galvanic corrosion.

General Attack corrosion

General attack corrosion takes over the entire surface area of a metal. The reason for this is either due to chemical or electrochemical reactions.

Localised Corrosion

Localised corrosion occurs in a particular area of a metal structure. It is split into three subcategories: pitting corrosion, crevice corrosion and filiform corrosion. Pitting corrosion causes holes within a metal structure, crevice corrosion takes place in standing water (most commonly at the joints) and filiform corrosion happens as moisture and oxygen infiltrate a structure’s coatings.

Galvanic Corrosion

Galvanic corrosion is also referenced as ‘dissimilar metal corrosion’. It occurs as two or more metals, unlike in their properties, make contact under water.

The difference between rust and corrosion

Corrosion is the broad title for the compromise of a metal’s integrity. It impacts a multitude of materials, whilst rust only targets iron and its alloys (such as steel). Rust is, therefore, an example of corrosion. Rust forms on iron or steel through oxidation, especially when moisture is present. With each flake of rust that pulls away from a metal’s surface, a new layer is exposed and compromised until it breaks.

Marine grade metals (nickel alloys)

Marine grade metals are those that can withstand underwater or wet environments, with minimal impact on their integrity. For the categorisation of marine grade, a metal must be able to withstand corrosive effects that typically occur in a water environment. The nickel alloys below are popular for their resistance against corrosion in a marine surrounding.

Alloy 600

Alloy 600 is a nickel-chromium alloy popular for its resilience against corrosion and heat. It has strong resistance to chloride-ion stress-corrosion cracking. Commonly used in marine environments for heat exchangers, steam generators, pressure vessels, exhaust systems, furnace components, including muffles, retorts and baskets.

Alloy 625

As a nickel-chromium alloy, Alloy 625 has strong resistance against pitting, crevice corrosion and stress corrosion cracking. It is used within marine environments in exhaust systems, heat exchangers and sea water piping systems. As a result of its high strength, it is key for structural components such as marine shafts, propeller shafts, pump and valve parts.

Alloy C-276

The molybdenum and chromium in Alloy C-276 allows it to create a protective oxide film on the surface of the alloy, which in turn strengthens its resistance to sea corrosion. As a result, it is impervious to corrosion in a multitude of harsh surroundings. It is ideal for use in elements such as propeller shafts, pumps and valves and for equipment exposed to sea water corrosion e.g tanks, reaction vessels, heat exchangers, condensers and pipes.

Alloy 400

The nickel-copper Alloy 400 is composed primarily of copper. Subsequently, it performs well in sea water environments. It is often used in the production of marine hardware and in the chemical industry for high temperature and pressure vessels, pipelines and other structural components.

Alloy C-22

Alloy C-22 is a nickel-chromium- molybdenum alloy with excellent durability against corrosion and high temperature strength. It is well suited for industrial heating, chemical processing and the filtration of liquids. Due to its properties, it can be used in harsh environments containing aggressive chemicals and in the marine environment.

Alloy B-2

Alloy B-2 is renowned for its strong resistance to corrosion, due to being made of nickel and molybdenum. It is used in chemical processing equipment such as pumps, valves, reactors, tanks, heat exchangers, condensers and storage tanks.

Alloy C-2000

Offering resistance to both chloride stress corrosion cracking and oxidising environments, Alloy C-2000 It can be used in chemical processing for paper production and for sea water applications such as piping, valves, pumps and tanks, alongside turbine blades and fasteners.

Metals (nickel alloys) resistant to heat

Heat resistant metals are used in a variety of applications and industries as they can endure high temperatures without compromising their integrity.

Heat exchangers are a pivotal component for industrial engineering. They allow heat from one medium to another for either heating or cooling. Most commonly used in automotive and HVAC systems, heat exchangers aid in the efficient exchange of thermal energy between two mediums such as liquids, gases and even between a gas and a liquid. Materials deployed in heat exchangers are metals such as stainless steel, copper alloys, aluminium, titanium and nickel alloys.

The top six heat resistant nickel alloys, and their uses, can be found below:

Alloy 600

With its nickel-chromium content, Alloy 600 can withstand temperatures of up to 2100 °F. This is due to its high level of oxidation resistance. It is used in furnace components and chemical processing equipment such as condensers and heat exchangers.

Alloy 800

This nickel-iron-chromium alloy can withstand temperatures of up to 2100 °F. As a result of its strong corrosion resistance, it can be used in furnace appliances, condensers and heat exchangers.

Alloy 825

Alloy 825 is a nickel-iron-chromium alloy with excellent heat resistance, capable of enduring temperatures up to 2100 °F. It is commonly deployed in components requiring strong corrosion resistance such as condensers and heat exchangers. As a result of its properties, it is used in the aerospace, electrical, nuclear oil and gas and marine industries.

Alloy C-276

The nickel-molybdenum-chromium composition within Alloy C-276 offers excellent heat resistance. It is capable of withstanding temperatures up to 2100 °F and is used for components that are subject to extreme environments such as flanges, valves and gaskets, heat exchangers and pressure vessels.

Alloy B-2

This nickel molybdenum alloy has a high level of oxidation and corrosion resistance. Withstanding temperatures up to 1000 °F, it is used for applications such as pumps, valves, reactors, tanks, heat exchangers and condensers.

Alloy X

Alloy X is a nickel-iron-chromium alloy able to endure temperatures of up to 2100 °F. As a result, it is utilised in furnace components and chemical processing equipment for condensers and heat exchangers.

Metals (nickel alloys) resistant to electricity

Metals resistant to electricity are invaluable in the electrical industry. They allow electrical wiring and components, power lines and common appliances to be constructed in reliable, safe and efficient way. In order to be highly valuable in this space, metals need to be not only resistant to electricity but also conduct it.

Alloy 400

Alloy 400 is composed of copper, making it highly resistant to corrosion from electricity. It is non-magnetic alloy well known for its thermal stability and low thermal expansion, alongside its resistance to a multitude of acids and alkalis. This makes it ideal for use in electrical switchgear, contacts, connectors and relays.

Alloy 600

Composed of nickel and chromium, Alloy 600 is durable against corrosion from electricity. It has strong oxidation resistance and thermal stability, is non-magnetic and has good strength. Alloy 600 is commonly used for thermal management applications such as high temperature cables, high temperature electrodes, electrical switch gears, contacts, connectors and relays.

Alloy 825

This nickel-iron-chromium alloy provides excellent resistance to corrosion from electricity, has brilliant thermal stability and has good weldability. It can endure a wide range of acid and alkalis and is non-magnetic. Alloy 825 is used for applications such as high temperature cables and high temperature electrodes.

Alloy C-276

Often used in electrical switchgear, contacts, connectors and relays, Alloy C-276 has excellent durability against corrosion from electricity.

Alloy B2

With its composition of nickel and molybdenum, Alloy B2 is highly resistant to corrosion from electricity. It can be used for electrical switchgear, contacts, connectors and relays.

Alloy X

Made up of nickel, iron and chromium, Alloy X is highly resistant to corrosion from electricity. It is suitable for use in electrical switchgear, contacts, connectors and relays.

Choosing the correct metal for its application is vital. It influences the mechanical ability and lifespan of a component, which can impact maintenance and financial cost. Let NeoNickel support you when choosing the neo-nickel alloy for your purpose. For help technical assistance, sales and more please get in touch.

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