How much difference can a single letter make? If you’re talking about NEMA 4 vs. NEMA 4X enclosures, you might be surprised at how important the difference can be. The two NEMA enclosure ratings have a lot in common, but there’s one big factor that sets them apart: resistance to corrosion. In this article, we’ll break down what enclosure buyers can expect from NEMA 4 enclosures and NEMA 4X enclosures. We’ll also give a quick overview of how corrosion works, and why certain types of devices may need NEMA 4X enclosures for corrosion protection.
Production operator operating centrifugal oil pump

NEMA Rating Basics

The National Electrical Manufacturers Association issues its NEMA rating system to help enclosure buyers easily evaluate an enclosure’s performance specs. The ratings are designed to categorize an enclosure based on its resistance to common environmental hazards, including:
  • Accidental contact with employees or tools
  • Airborne dust and debris
  • Falling dirt
  • Weather conditions such as rain, snow and sleet
  • Splashing, dripping and hose-directed water
  • Submersion in water
  • Corrosion
Each NEMA rating signifies a degree of protection against one or more of these environmental conditions. To learn more, make sure to read our NEMA ratings guide.

NEMA 4 Enclosures vs. NEMA 4X Enclosures

NEMA 4 enclosures and NEMA 4X enclosures are both popular across many different industries. Both ratings indicate a waterproof and dust-tight enclosure that’s suitable for general outdoor use or heavy duty indoor use. More specifically, both ratings provide an excellent level of protection against adverse weather conditions, repeated hose washdowns and airborne particulates such as windblown dust. However, a NEMA 4X enclosure has an additional feature that a NEMA 4 enclosure lacks: protection from corrosion. Corrosion can be a big problem in many different enclosure applications, and a NEMA 4X enclosure can help protect your devices.

What Is Corrosion, and Why Should You Care?

Corrosion is nature’s way of converting metals such as steel into more chemically stable forms, such as iron oxide (commonly known as rust). At the most basic and simplified level, corrosion happens when a piece of metal has its electrons “stolen” through a reaction with electrolytes such as water, salt and/or certain chemicals. When the metal loses enough electrons, it begins to degrade and turn into oxidized materials such as rust. Unfortunately, while nature may like the chemical stability of these corrosion products, they’re not much good when it comes to functioning as part of an electrical enclosure. Corrosion seriously compromises the structural integrity that an electrical enclosure needs to maintain in order to do its job of protecting the sensitive components inside. A corroded enclosure will often become pitted or scarred by the corrosion. When left unaddressed, corrosion can create holes and cracks in an enclosure that compromise its protection and allow ingress of water, particulates and other hazards that will severely damage electrical components. That’s why it’s important to choose a NEMA 4X enclosure when your application requires corrosion protection. Old electrical enclosures box

Corrosion Protection from NEMA 4X Enclosures

A NEMA 4X enclosure is rated to provide additional protection against corrosion. That protection can take several forms, including materials that are naturally resistant to corrosion (such as stainless steel and aluminum) or an anti-corrosion coating. All of these are proven effective against corrosion when properly maintained and cared for. Non-metallic enclosures, which are made from materials such as polycarbonate, are also naturally resistant to corrosion. Due to differences in chemical structure, plastics aren’t affected by corrosion in the same way that metals are. These properties mean that NEMA 4X non-metallic enclosures are among the best choices for enclosure buyers who need corrosion-resistant enclosures.

Are NEMA 4X Enclosures Totally Corrosion-Proof?

NEMA 4X enclosures provide much better protection against corrosion than standard NEMA 4 enclosures, but they can still be vulnerable to corrosion when not properly cared for, particularly in the case of metal enclosures. Likewise, polycarbonate can still be vulnerable to other forms of degradation from harsh chemicals, so use a chemical compatibility list to ensure that any chemicals used to clean the enclosure won’t damage it. Enclosures should receive a regular cleaning with a mild, neutral solution to help remove salt, chemicals and other materials that can act as electrolytes and create vulnerability to corrosion. After cleaning the enclosure, make sure to wipe it dry.

NEMA 4 and NEMA 4X Enclosures from Polycase

Polycase offers our customers the best in NEMA 4 enclosures and NEMA 4X enclosures. You’ll find great options such as our AN Series diecast aluminum enclosures and our SA Series stainless steel enclosures, two elegant metallic enclosure series designed for corrosion resistance and made with weatherproof silicone gaskets. Our non-metallic enclosure options are equally strong, with popular corrosion-resistant choices like the polycarbonate ML Series available. Polycase ML-34F

Polycase ML-34F

Do you have more questions about the key differences between NEMA 4 vs. NEMA 4X enclosures and how you can keep your equipment safe from corrosion? Our enclosure experts will be glad to help. Give us a call at 1-800-248-1233 or contact us online for the latest information on our waterproof enclosures and corrosion-resistant enclosures.
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