# Static discharge of large items (metal)

We have a cabinet which is flushed with dry air and the metal instrumentation inside it tends to build up an unwanted charge. Obviously parts of the machinery are not sufficiently earthed (working on it).

However, is there any kind of sticky conductive tape coated with spikes/needle that might act to ionise the air and self discharge?

• Ionizing the air will not help, unless you know exactly how much opposite charge you want to neutralize, which you don't. Earthing the machinery should suffice I think. – Bimpelrekkie Sep 30 '16 at 11:21
• Buy copper tape on ebay. Search for copper tape conductive adhesive. That should be able take care of all your static grounding needs for less than $1. – Dampmaskin Sep 30 '16 at 11:34 • Static dissipative surface treatments are usually 1e9 to 1e11 Ohms per Square. Would an anti-stat carpet spray be useful or a dust collector? – Tony Stewart Sunnyskyguy EE75 Sep 30 '16 at 11:35 • I am not looking for a conductor specifically but something "spikey" that can dissipate the charge through the tips of the spikes pushing up the field strength until they ionize the air. – Dirk Bruere Sep 30 '16 at 11:37 • @DirkBruere, metal spikes need about a kilovolt to "turn on," so they're best for reducing 20KV down to 2KV. Torn carbon-fiber cloth from plastics store works well. Better would be to identify and eliminate the source of charging. Is it from human arms bumping the equipment? A simple electrometer (jfet w/floating gate) would easily sense any charged air. Moving air doesn't create any contact electrification unless it's causing dust-impact. – wbeaty May 13 '17 at 6:52 ## 2 Answers If you can't just connect a 100meg resistor to ground, then "discharge wicks," tufts of carbon fiber, steel wool, or metal combs tend to work fine at reducing your floating kilovoltages down to ~1KVDC. Below that, the sharp-tip coronas turn off. Traditional methods include radioactives: thorium-steel rods, etc. Perhaps a welder tip from a TIG welder; tungsten-thorium ionizer rod would be enough. Otherwise, get yourself an ionizing blower,$50 on ebay, and aim it at the equipment. These produce balanced populations of pos/neg ions, in other words, converting the air itself into hundred-meg resistors.

You can buy ion generators that will produce a flood of ionized air. They are not passive devices- they have a high-voltage supply inside.

They are often used in industries that have a high velocity web made of non-conductive material that can pick up static charge- for example for blown film production.

As well as costing significant money, they tend to produce ozone, which plays havoc with rubber (it destroys it). If whatever it is that is picking up charge is conductive, it's going to be a lot better just to ground it, even if you have to add a slip ring or something of that ilk.

• Thanks, but I was thinking of using needles to induce a self discharge into the atmosphere – Dirk Bruere Sep 30 '16 at 15:08
• I've never seen anything like you describe. There are spikes used on aircraft to control static. Maybe try making something by sandwiching some sharp needles using copper tape with conductive adhesive. – Spehro Pefhany Sep 30 '16 at 15:28
• Yep, "ionizing blowers" or fans, about \$30 on eBay. Essentially they render the air conductive, so charge will leak off of any surfaces. – wbeaty May 13 '17 at 6:54