Electrically Insulative Coating for Steel?

[ajensen]

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.

 

[kingnero]

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?

 

[IRstuff]

Why is there even a voltage on this part? Typical design rules prohibit using structure to conduct current.

You could try some sort of anodization

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[ajensen]

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.

 

[IRstuff]

Anodization is not a powder coating

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[MintJulep]

Kapton tape.

http://www.kaptontape.com/1mil_Kapton_Datasheet.php

 

[ajensen]

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?

 

[ajensen]

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?

 

[MiketheEngineer]

Make the part from plastic, wood, etc??

 

[ajensen]

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.

 

[unclesyd]

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.

 

[ajensen]

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?

 

[Yagonyonok]

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.

 

[unclesyd]

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.

 

[KENAT]

Vaguely relevant thread332-287894

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MintJulep]

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.

 

[Ron]

Ceramic coating.

 

[IRstuff]

My bad, I was using incorrect terminology for steel. I was thinking more along the lines of blueing or Parkerizing, which supposedly are nonconductive.

TTFN

FAQ731-376
Chinese prisoner wins Nobel Peace Prize

 

[sreid]

I think that a Parylene coating might be a good choice for you.

http://www.conformal-coating.com/parylene_coating.htm

 

[ajensen]

sreid,

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