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Electrically Insulative Coating for Steel?

Electrically Insulative Coating for Steel?

Electrically Insulative Coating for Steel?

(OP)
Hi,

I have a small stainless part (think washer, but irregularly shaped) that is about .250" in diameter and between .005" and .010" thick.  The part holds a mating piece in position and is designed with fairly tight tolerances (+/- .001" around the profile).  I need to electrically insulate this part and am wondering if there is a very thin coating/plating (less than .001") that will do the job.  Does anyone have suggestions for a process that might work?  Keep in mind the final part dimensions still need to be held to within +/-.001" so whatever coating/plating process is used must be accurate and repeatable enough so that the post-coated/plated dimensions are in spec.  The coating/plating does not need to be a super insulator as we are only dealing with less than 4V and less than 600mA.   

RE: Electrically Insulative Coating for Steel?

I haven't tried so but I'd think powdercoating might work,
as it's basically a plastic film.

Are they no other (better) options like changing the design, the material, or sleeving the washer in an insulating material?

RE: Electrically Insulative Coating for Steel?

(OP)
At this point changing the design is not ideal.  My concern with powder coating is that it would be too thick and possibly not precisely enough controlled.   

RE: Electrically Insulative Coating for Steel?

(OP)
Hi IRStuff,

I am actually trying to prevent the voltage going through this part.  I want to insulate it from a voltage passing through a circuit beneath it.  

I believe anodizing can only be done on Al, no?  Also, does anodizing electrically insulate its base substrate?

RE: Electrically Insulative Coating for Steel?

(OP)
Thank you, MintJulep.  Can Kapton be cut very precisely?  Would it be possible to apply the kapton to the steel sheet (via adhesive) before cutting, and then laser cut both steel and kapton at the same time so that the kapton profile matches up precisely with the steel kapton?

RE: Electrically Insulative Coating for Steel?

Make the part from plastic, wood, etc??

RE: Electrically Insulative Coating for Steel?

(OP)
Mike,

The trouble with plastic or wood is the strength.  The part is only .010" (or possibly less) thick x ~.25" diameter, and it needs to locate another part, so we want to make sure it's not flimsy at all and that it does not deflect or bend.  Not much load will be placed on it, though, so a hard plastic may be an option as long as we can achieve the tight profile tolerances.  Thanks for your suggestion.

RE: Electrically Insulative Coating for Steel?

We use DuPont Tedlar Film alone and with adhesive backing in our Electrolytic Process.  
There Technical Staff were easy to work with and know there stuff.

http://www2.dupont.com/Tedlar_PVF_Film/en_US/index.html


Addenda:
I have a sample of the material from the first production run made 6=50 years ago. It was a piece of this material that I tested 15 years later for use one of our Electrolytic Sells.  The Tedlar overcame a major problem with stray currents in the cell.
 

RE: Electrically Insulative Coating for Steel?

(OP)
unclesyd, thank you very much for the recommendation.  Is the Tedlar superior to Kapton in terms of electrical resistance (to act as an insulator)?  Is it easier to process, etc?  Why might one use a Tedlar backing as opposed to Kapton for my application?

RE: Electrically Insulative Coating for Steel?

ajensen,
If you can get away with using aluminum, then I would go with an anodized part, as IRstuff suggested.  Anodic coatings are electrically resistive, and should work well for you, that is if you can use aluminum rather than stainless steel.

Use of product voids warranty.

RE: Electrically Insulative Coating for Steel?

I haven't looked it up but I believe that Kapton is a far better insulator than Tedlar.

Our main criteria was for process compatibility. Tedlar was far
superior in that respect.  At the time there was large difference in cost with Tedlar being the least expensive.  If my memory serves me right I believe that you could also get Tedlar in wider widths.  
I can't recall the difference in electrical conductivity between the two.  In our application we were using it to isolate components with a 60 VDC potential difference.   

 

RE: Electrically Insulative Coating for Steel?

Kapton was developed to be an insulator.  Tedlar was developed for the graphics industry if I recall.  To be bus wrap, outdoor signs and such.

So yes, Kapton is a far better insulator than Tedlar.

For a 4 volt differential Tedlar would probably be fine.  In fact, Scotch tape would probably be fine.

I don't think either Kapton or Tedlar could be neatly cut simultaniously with your washer.  But maybe it could.

RE: Electrically Insulative Coating for Steel?

Ceramic coating.

RE: Electrically Insulative Coating for Steel?

(OP)
sreid,

The Parylene coating is a very intriguing idea - I will look into that, thanks!

RE: Electrically Insulative Coating for Steel?

What voltage must be resisted?  

0.001 thickness of anything will prevent very, very little voltage.  Worse, it can too easily be scratched through, nicked, sliced etc during assembly/re-assembly/repair and lose any resistance.

Make the whole thing of your plastic.   As a locator of the next part and not a retainer or bolt or prying point of stress, you'll see only minor pressures that can easily be withstood across such a small distance.    

RE: Electrically Insulative Coating for Steel?

ajensen,

   If you need a hard, accurate, non-conductive washer, how about some sort of machinable ceramic?

   Ask your machine shop what they like.

               JHG

RE: Electrically Insulative Coating for Steel?

paralene is a good insulator but is easily scratched and is usually only about 0.0001" thick

MACOR is an excellent machinable ceramic but would be subject to fracture if subject to any bending - meaning the mating surfaces must be flat

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