Corrosion Protection for Offshore Marine Equipment

Protect your sensitive equipment in severe marine environmental conditions with a NEMA 4X extreme weather rated stainless steel electrical enclosure.

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When it comes to protecting against wind, rain, sleet, snow, hail, salt water, and corrosion it’s all in the steel used in the enclosure – 316 stainless steel in this case.

Stainless steel is finished not only for aesthetic purposes, but also to improve its corrosion resistant properties. As it is worked to obtain finer finishes, the average surface roughness decreases thereby, improving the corrosion resistance of the metal.

In addition to surface finish quality, the grain orientation of a stainless steel enclosure can have a significant impact on corrosion resistance. A vertical grain orientation can help to provide an easier, more thorough cleaning since rainwater and gravity fed hose water will run parallel to the grains. By contrast, horizontal grain lines may retain corrosive contaminates, thereby expediting the corrosion process.

Exactly how a metal will corrode in a given environment is often difficult to predict. The climate of a particular region can have a large impact on corrosion characteristics. Coastal areas can be affected by airborne salts carried over long distances by strong winds so special attention must also be given to not only the general climate of the region where the enclosure will be installed but also to potential microclimates of the specific enclosure location. Nowhere is this more evident than cold regions where de-icing is a regular occurrence.

The first priority for industrial enclosures is to protect the electronics inside. Therefore, placement of the electrical enclosure in an area where it won’t get wet is best whenever possible provided the enclosure is cleaned regularly.  Covering the enclosure with a shield or placing it under an eave will prevent water and/or ice damage. However, there is also a downside. By covering the enclosure rainwater is unable to wash contaminates off of it which could cause significant corrosion to the stainless steel over time. So if you’re going to cover your enclosure make sure you clean it regularly.

Higher humidity and lack of ventilation may also be factors. That’s why it’s also a good idea to refer to the NEMA rating for the enclosure to provide the best electronics protection available for a marine environment.


The National Electrical Manufacturers Association (NEMA) has developed the NEMA 4X rating for stainless steel electrical enclosures to address the effects of atmospheric corrosion. An enclosure carrying the NEMA 4X rating meets certain minimum conditions of corrosion resistance. Specifically, the material from which NEMA 4X rated enclosures is built must withstand two hundred hours of salt spray with minimal evidence of corrosive pitting.

According to NEMA standards, stainless steel, “Type 4X enclosures are constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of  protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); that provides an additional level of protection against corrosion; and  that will be undamaged by the external formation of ice on the enclosure.”

We build a variety of NEMA 4X rated electrical enclosures for offshore, marine, and corrosive atmosphere applications. We found that 316 stainless steel is the most corrosion resistant material for constriction; due to its higher Nickel content and the addition of Molybdenum. We also found that although 316 stainless steel is the best material for corrosion resistance on the body of the enclosure it is not the best material for hardware (nuts, bolts, and fasteners). It’s been our experience that 304 stainless steel has higher strength and wear resistance than 316L stainless, due in part to its slightly higher Chromium content. With higher strength and wear resistance and a lower cost than 316 hardware we recommend 304 over 316 as a better choice for hardware on any stainless steel electrical enclosure that will be exposed to marine environments.

The bottom line is that when it comes to protecting your sensitive equipment in severe marine weather conditions, NEMA 4X rated stainless steel electrical enclosures will get the job done right for a long time.

Nema Enclosures designs and fabricates quality NEMA and UL rated stainless steel and aluminum electrical and instrument enclosures to your exact specs & that meet your lead times. We believe that by thinking about your enclosure needs while you’re configuring what goes into it will save you time, money and frustration.

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