What metal should you use?
Choosing the right metal is not always a simple process. For many industry applications, it’s a three-fold decision; making sure you find the most cost-effective material that has the suitable properties and corrosion resistance for your application.
This article weighs up the different properties of the various metals available, helping you find the right option for you.
Aluminium is one of the most light-weight and durable metals available, offering a high strength to weight ratio. It is highly resistant to corrosion and sound, which makes it a useful for applications such as acoustic panels and HVAC equipment where noise control and durability is important.
It is also suitable for environment where there may be a fire, as it does not burn nor does it give off noxious fumes when exposed to fire and heat. This makes it suitable in environments such as kitchens.
Aluminium is a cost-effective material and is highly sustainable; it can be repeatedly recycled through a simple re-melting process.
The most desirable quality in steel is its strength, which is why it is commonly found in industrial machinery and agricultural equipment. However, unless it is plated or painted with a protective finish, it can be susceptible to rust.
Like aluminium, steel is a useful tool in controlling sound, so again can be used in acoustical applications or on equipment whereby you want to diffuse sound emitted from noisy machinery. Due to its noise-controlling abilities and strength, it’s a popular choice for machine guards, screens, grilles and panels.
It is also a sustainable material, produced from recycled material.
Stainless steel is a steel alloy consisting of at least 11% chromium, which creates a protective film around the metal and gives it its shiny appearance.
If the protective film is scratched, the metal will repair itself unlike zinc plating (see below), which if scratched can cause corrosion to spread beyond the scratch).
This type of metal retains the strength of steel in its unprotected state, but has the added benefit of being corrosive-resistant against air and moisture. It is not however, always suitable for environments with low oxygen levels or applications that will expose the metal to strong acids or high levels of salt. Different grades of stainless steel will provide different levels of resistance against corrosion, which you can read more about here.
Stainless steel is often used in the catering industries, as it can be steam cleaned and it is also popular in the pharmaceutical industry as it provides a clean, antibacterial surface. Other more general applications may include components in white goods and machinery, stairs, filters.
It may be more expensive than mild steel but has a greater aesthetic and offers greater durability.
Similar to stainless steel, galvanising offers a greater resistance against rust. It is a process of adding a protective coating of zinc to steel and one of the most popular method of doing so is hot-dip galvanising. This involves dipping the steel into a molten bath of zinc, leaving a coat of pure coat on the outer surface.
It is one of the most cost-effective solutions to protecting the steel and once coated it is easier to maintain and lasts longer.
Unlike stainless steel however, it does not offer the greatest aesthetic finish. This means it may not be the most suitable metal for decorative applications.
Brass is an alloy of zinc and copper, which makes it highly resistant to corrosion. This, coupled with its stunning gold-like appearance, is the reason it is popular in decorative applications.
This metal allows good airflow and ventilation, as well as offering excellent sound control. It’s a strong yet slightly malleable metal; and whilst its flexibility is advantageous in certain areas, it makes it unsuitable as a weight-bearing material. However, its strength and ductility can be altered depending on the varying mixture of zinc and copper.
An alloy of mainly copper, bronze offers excellent resistance against metal on metal friction. This makes it a popular metal for industrial applications such as bushings and bearings. It is also a popular metal in the marine sector due to its corrosive-resistant properties.
Phosphor bronze offers a low coefficient of friction and a high fatigue resistance. The element of tin improves the tensile strength, whilst the phosphorous content increases the wear resistance and stiffness. This type of bronze material is popular for components such as springs and washers.
Aluminium bronze on the other hand has increased strength, which makes it suitable for manufacturing components, marine equipment, bearings, pumps and equipment that is in contact with corrosive fluids.
Silicon bronze contains both brass and bronze, offering moderate strength and fairly good corrosion. It is usually chosen for it aesthetic qualities more than anything else, for example catering equipment.
Copper is commonly used for pipes and fittings, as it offers electrical and thermal conductivity, strength and resistance to corrosion.
It can be created from recycled materials and is 100% recyclable itself as it can be easily soldered and brazed.
Monel is a nickel and copper based alloy that offers strength and ductility. It is also resistant to acids and alkalis, which is why it is a popular metal in chemical plants. However, it can become pitted if it is exposed to salt water or corroded if exposed to substances including nitric oxide, nitrous acid, sulphur dioxide and hypochlorite.
Monel can also speed up the corrosion of other materials such as aluminium, zinc or iron.