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We have auluminum (Al) cabinets that we have applied a Black anodized coating to. Is that sufficient to avoid static shock and will it then not need to have ground studs installed since it is black anodized?

Hi Ron,

Thank you for your question regarding static electricity and anodized aluminum cabinets.  It is our pleasure to help.

The short answer to your question is that “yes” you need to ground the cabinet.  Please see the ESD Association Guidelines and the ANSI/EIA/TIA-J-STD-607-A for further information regarding cabinet grounding for static control.

When it comes to static control, the story of the ‘Three Little Bears’ provides good guidance.  In the story, the porridge is either too hot, or to cold, but one was just right.  When it comes to static control, materials can’t be to conductive or too resistive (insulative), they have to be “just right”.  Highly conductive materials will allow the quick flow of static electricity, which can damage sensitive gear.  Insulative (or resistive) materials actually allows static electricity to form and even stores it.   It is not uncommon to see simple plastic sheets form static voltages that can be measured in excess of 20,000-volts!  The trick with static control is to provide materials that are not to conductive and not to resistive, but are “just right”.

Once you have a “just right” material, you still need to get the unwanted static charge to ground.  Otherwise, you are going to charge the unwanted object to its maximum capacity, where it will be forced to eventually discharge itself through your computer components.

Anodizing is an electrolytic passivation process that adds a thin layer of oxides to the surface of the aluminum in order to help reduce the effects of corrosion.  This thin layer is in fact non-conductive (insulative), however it is also extremely porous.  The Anodizing process is well known to leave many microscopic fissures on its surface, which provides an imperfect layer.  However, even if your aluminum cabinets were in fact perfectly anodized, you would have only have generated a worst case scenario for static charges, as non-conductive materials form the high static voltages.

In conclusion, good static grounding for aluminum anodized cabinets includes not only an effective ground path, but also a grounding electrode with a resistance-to-ground of less than 5-ohms ( a difficult standard to achieve).  The ANSI/EIA/TIA-J-STD-607-A standard has many requirements for grounding which not only includes your cabinets, but also the metallic conduit carrying the data lines, the metal air conditioning units, the fire protection system, pedestals, cable trays, and more.  All of these systems must be bonded to ground, especially when dealing with computer servers and other sensitive electronic equipment.

We hope you find this information useful.  If you should have any further questions related to static control or server room grounding, please do not hesitate to call one of our engineers directly and they will be glad to discuss your project free of charge.

Best regards,

The Engineering Team at E&S Grounding Solutions

 

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