Crude coil sheilding paint

[Kev]

Hi,
There's been a number of posts over the years related to coil shielding paint, what to use, how to home-brew etc., but nothing I've tried has been acceptable. I resorted to using Electrolube Nickel loaded paint, but my Minelabs don't like it, plus the cost is exorbitant nearly $60 US per can where I live, although that's retail, and not the trade price.

Anyway, I may have a solution for the 'poor' home-brewers, give it a try and see what you think.

Cheers
Kev.

destructions here => http://download511.mediafire.com/n7s...ding+paint.pdf
P.S. Let me know if you have problems downloading the pdf

[Kev]

Hi Guys,
I must apologise heaps for the file hosting site I've used......I didn't know they pushed so much garbage, or had popups, please don't click on anything you don't need to......I should've realised it was too good to be true.....I'll look for a better site that doesn't use tacky schemes.

Sorry
Kev.

P.S. when I click the link I don't get the garbage, but when I click the link on another computer yucky, so it must remember IP addresses and display accordingly.

[Qiaozhi]

Hi Guys,
I must apologise heaps for the file hosting site I've used......I didn't know they pushed so much garbage, or had popups, please don't click on anything you don't need to......I should've realised it was too good to be true.....I'll look for a better site that doesn't use tacky schemes.

Sorry
Kev.

P.S. when I click the link I don't get the garbage, but when I click the link on another computer yucky, so it must remember IP addresses and display accordingly.

Why don't you just post the document here on Geotech?

But just for the record ... if you use Firefox (with AdBlock) in Linux you don't see any of the garbage. It's just a straightforward download.

[Kev]

Thanks Qiaozhi,
I wasn't aware I could upload it here. Even with Firefox once I closed it I was left with windows I didn't open

File attached here now.
Cheers
Kev.

P.S. I must learn to spell properly........ i before e except after c...etc.,

[simonbaker]

Always good to have another option.

Takes me back to childhood, taking apart batteries for carbon rods, etc. No wonder I'm brain damaged...

-SB

[Kev]

Gid'day SB,
Me too!
I was extracting the carbon rods and grinding them down to make paint without much success, then I found out the black paste already had carbon grains in it, so I gave that a go, and viola! saved the coil from the rubbish bin.

Cheers
Kev.

[ron_o]

Hi Kev
In your file download you suggest using a fast drying xylol solvent based paint. May I suggest the use of a xylol / vinyl based paint as it is more chemical resistant and less likely to break down and flake off over time.
Regards
Ron

[Altra]

Hello Kev,

Your improvisation is very clever. Have you ever tried "lamp black" as your base? I read an electro-dag data sheet a while back and it mentioned lamp black as a main component? I bought a small bottle of it in the paint store, but have not tried any experiments.

Great stuff
Mark

[Kev]

Hi Ron & Mark,
Good suggestions Guys. I just tried what I had on hand and as these are ready available worldwide, I thought I'd share. I'm applying the paint to HDPE foam coil former inserts, and this paint sticks very well, However you are correct Ron, if this was applied to the inside of a plastic coil shell, any shell flexing, as it does, would cause cracking and resistance would go up so it would be best to use a more flexible paint as you say, even one a that has ketones in it so it bites into the plastic surface, or one could spray an overcoat of vinyl based lacquer over the conductive paint to give it support and flexibility without cracking.

Mark I've not seen lamp black in the shops here, so I've not tried it. It may go under another name here....stove polish or something??? In the batteries it's called acetylene black, basically just soot

The thing about batteries is that all the components in the paste are conductive, so these provide a conductive colloidal suspension between the carbon spheres....at least that's how I imagine it.

Cheers
Kev.

[grungymike]

graphite?

While reading this thread I got to wondering if a graphite based dry lubricant would work as a conductive powder for a homemade shield paint? I've seen that stuff available in hardware and auto supply stores.

gm

[Kev]

G'day gm,
I did try the graphite powder you mentioned, and yes it did work for me using the Plasti-cote paint. There are a couple of reasons why I didn't like it as much as the battery emulsion though.

I had to send away for mine and it cost $7 U.S. for 15 grams, and I'm not sure, but I'd be lucky to completely shield a large coil with that.

I also found I needed to use quite a lot of graphite power in the mix which made the paint crusty, and more likely to flake, but I guess I could've coated it with a lacquer to give it strength. (more expense)

At a mixture level where I didn't want to dilute the paint any more for fear of flake off, the average resistance was around 2,500 to 5000 Ohms per inch, well over double what I was wanting.

The solution I came up with was so cheap and simple in comparison, and the results are that my refurbished coil is running better than new.

Maybe a mixture of graphite powder and chimney soot would work a little better, if you experiment and find a better solution let us know.

Cheers
Kev.

[Ferric Toes]

I resorted to using Electrolube Nickel loaded paint, but my Minelabs don't like it, plus the cost is exorbitant nearly $60 US per can where I live, although that's retail, and not the trade price.

Hi Kev,

The likely reason that nickel paint upsets Minelabs is because it is magnetic. If you look closely at the receive waveform of a nickel paint shielded coil, you will see a decay curve that is not due to conductivity but caused by magnetic viscosity. I have also tested nickel paint in my magnetic susceptibility meter, and my soil viscosity meter, which confirm the above. A nickel paint shielded coil often buzzes or sings when it is powered up due to its reaction with the pulse field and the coil shell acting like a sounding board.

Eric.

[grungymike]

custom shielding paints.

Yipes, I was gonna pay $35 + shipping for that nickel spray! Think I'll do a little more research first. One possibility comes to mind, there's a product called "coppercoat". It's a spray adhesive used on head gaskets during engine assembly. It's got colloidal copper in what I think is an acrylic polymer base. No idea what the electrical characterisics are like, might be worth trying. Same thought for some of the fine powdered metal flake additives used in custom automotive paints. As I'm thinking (?) while typing, I wonder if part of the reason soot or carbon black works well has to do with the REALLY small particle size, as well as high conductivity.

I'm still working on building a control box, haven't gotten to coil building yet. Learning more every day from this site though...

gm

[Kev]

Hi Eric,
Thanks for sharing that, it all makes sense now, no wonder it was making goldfield ground balancing so difficult

Eric, I would also like to take this opportunity to extend my warmest condolences to you, and your family for your sad loss. There are a lot of people around the world who really care about you, and will always be grateful to you for your open contributions to metal sensing technologies.

Kind regards
Kevin Murta.

[homefire]

Just a thought!

Has anyone tried Aluminized or Crome Paint?