Enclosures can be made from a range of different materials, and these can broadly be divided into metals and plastics. There are six main enclosure materials you need to know about: GRP (glass-reinforced plastic, aka fibreglass), mild steel, stainless steel, aluminium, ABS (thermoplastic) and polycarbonate (thermoplastic). These materials all have advantages and disadvantages. This article is going to go through all of them so you can make an informed choice about the type of material to buy an enclosure in.

Metals:

Mild steel

Mild steel is an alloy of iron, carbon and other elements, depending on what properties the metal has. The main ingredient is iron. Mild steel has a lower amount of carbon than other types of steel. It is a very versatile metal, and the slightest addition of other elements can transform its properties, making it suitable for a wide range of uses and environments!

For enclosures, mild steel is a good option for indoor enclosures. Its strength lends it to floor standing or wall-mounted enclosures and it is an economical choice that can be cost-effective as an enclosure solution that can work well for control panels in standard environments. 

Mild steel is not an ideal option for outdoor environments. Although mild steel enclosures are still IP rated, when it comes to water, constant exposure to water will cause mild steel to corrode at a faster rate than any other enclosure material.

Stainless steel

Stainless steel is an alloy of iron which features a high chromium content as well as some other elements to give it unique properties. The main ingredient is still iron, but with stainless steel, at least 11% is chromium.

Stainless steel, as its name implies, is very resistant to corrosion and rusting when compared to other iron alloys such as mild steel or cast iron. It has a unique property that it is easy to sanitise, which is why stainless steel is sometimes used in hospital applications, such as surgical steel.

When it comes to enclosures, stainless steel is ideal for pharmaceutical, food processing and medical industries as it can be sterilized more easily than other enclosure materials. 

The two main types of stainless steel used for enclosures are 304 & 316 grades. 304 stainless steel is one of the most common used around the world, due to it’s good corrosion resistance and cost. It is widely used in sterile environments such as the food industry. It does, however, have a weakness, it is susceptible to corrosion in saline environments, such as near the ocean. 

In these environments, 316 stainless steel is an excellent choice. The addition of molybdenum at 2-3% allows 316 stainless steel to deal with much harsher chloride environments. Often regarded as “marine grade”, 316 stainless steel is the ideal choice for marine and coastal applications. 

Although stainless steel is more expensive than mild steel, it is also more resistant to corrosion so it will likely last longer. Stainless steel is perfect for harsh environments so can be used in indoor or outdoor applications, making it more versatile than mild steel. Some stainless steel can be magnetic.

Stainless steel is not ideal for situations where electrical conductivity is an issue, because it is a conductive metal (although not as conductive as copper). Where the enclosure needs to be an insulator, plastics or GRP are better options. Additionally, in high heat, stainless steel will expand, meaning enclosures subjected to extreme heat could deform.

Aluminium

The last metal used for enclosures is aluminium. This has no iron content, as it is a separate chemical element with different atoms to iron. Aluminium is never magnetic, but it is an electrical conductor. 

The weight is less than a third of the weight of steel for the same quantity, making it a lighter option for enclosures.

In terms of corrosion, aluminuim forms a thin oxide layer that protects the rest of the metal from corrosion, making it a great choice for corrosive environments. It’s also better with temperature extremes, which sets it apart from plastics.

Aluminium is most often seen in junction boxes and other small enclosures.

Plastics

Plastics are not classed as conductive, meaning they are great for use in high-voltage environments to stop current leakage during normal operation or if a fault is found. ABS & Polycarbonate material can share the same injection moulds, so you will usaully find most enclosures are available to purchase in both options. 

ABS

ABS is derived from polystyrene but it’s a stronger plastic due to the production process and added ingredients. ABS has good hardness, rigidity and chemical resistance, making it a cost-effective, lightweight, non-conductive choice for indoor enclosures. 

Another nice thing about ABS is the shiny finish. This produces great looking enclosures with excellent water resistance. 

One disadvantage of ABS is the fact that it is less UV resistant than polycarbonate. This means polycarbonate is a better choice for enclosures that are going to be situated, stored and used outdoors on a regular basis, as they will withstand the UV light better.

Polycarbonate

A complicated name for the majority of plastics, polycarbonates include lots of different types of materials with different properties, known as “thermoplastic polymers” (there are other types of plastics as well). 

Thanks to excellent UV stability, polycarbonate enclosures are ideal for outdoor applications. And like ABS, polycarbonate is also very easy to machine, meaning it can be used for fast, accurate production of machined enclosures such as those used for control panels. Polycarbonate is the material used to make clear/transparent enclosure lids.

The downsides are that this type of plastic is not as strong as other materials such as GRP or steel. And while most polycarbonates tend to have much higher melting points than other plastics, they can’t compare to the melting points of steel or aluminium, so in environments where heat is a potential issue, a different enclosure material might be better.

GRP

Short for “glass-reinforced polyester”, GRP is also sometimes known as fibreglass. It is a composite material famous for its strength and durability. As it is easy to maintain and can’t corrode, it is a popular choice for marine environments and anywhere else that requires strength and low corrosion risk. GRP is also non-conductive of electricity and heat, which is why it is a very popular choice in the rail industry and the main material used in Class II railway design. 

Like polycarbonate, GRP can be formed in a way that gives it an excellent IP (ingress protection) rating.

Another advantage of GRP it is easy to machine, for example cutting or holes being bored into the enclosure are straightforward tasks. However the internal fibres are highly abrasive, meaning the cutting tools will wear down fast, as well as creating hazardous dust particles in the process. To learn  more about how we can machine your GRP enclosures, get in touch.

Conclusion

To sum up, these are the main enclosure materials used in electrical enclosures. You can read about them in more depth in separate articles if you want more technical details. To buy enclosures, visit the enclosures tab at the top of this page.