EMI/RF

[GEuser]

Q

[T3sl4co1l]

Good to know.

I've seen a "stainless steel loaded" product that, practically speaking, didn't seem to be much more than heavy gray paint.  Didn't do anything for RFI.

Conversely, I've used boxes lined with the stuff (real, usefully conductive paint, that is; usually a silver to golden color), which did a fine job.  It's pretty awesome seeing ~kV ESD pulses simply wash over and around a plastic box, with >40dB isolation on the inside.

They're even available with IP67 or similar ratings, which surprised me.  The gasket looked like a white o-ring that someone dropped in a little dust, but it's actually quite conductive, and keeps water out!

Tim

[Ian.M]

For 'cold galvanising' to be effective against corrosion, the zinc particles must make electrical contact with each other and the substrate, so there is an incentive for the paint manufacturer to come up with a conductive formula even though that's not its intended use. However it will oxidise more readily than a Nickel based screening spray, loosing conductivity with time,  so you may need to over-coat it with lacquer to protect it.

[Cerebus]

For 'cold galvanising' to be effective against corrosion, the zinc particles must make electrical contact with each other and the substrate, so there is an incentive for the paint manufacturer to come up with a conductive formula even though that's not its intended use. However it will oxidise more readily than a Nickel based screening spray, loosing conductivity with time,  so you may need to over-coat it with lacquer to protect it.

I'm out rural (farming country) with a lot of steel gates and the likes out in the weather 24/7 and from practical experience i have yet to see any of these products like this "corrode" , i have seen new galvanized gates corrode just after a few months yet cleaning them up and then applying a coat brings them back to new looking , and i just looked then at a get next door that was done 3 or 4 years ago and it still looks new , practical experience .

So as far as a gadget sitting inside any concerns of corrosion is laughable imo .

I think you're misunderstanding Ian.M. He's saying that for this paint to do its job as an anti-corrosive galvanizing spray it is required perforce to be conductive and that's a useful side effect from our point of view so it makes good shielding.

The mechanism for it protecting your gates is that the zinc preferentially oxidises instead of the steel. Zinc isn't a particularly noble metal, it corrodes quite easily. Zinc granules, that you'll find in any chemistry laboratory, always have a fine coating of white zinc oxide. In galvanization it protects by corroding away over time as it donates electrons to the iron which requires a galvanic path between zinc and iron.

Ian.M's concern is that, in the shielding use,  natural surface oxidisation of the tin particles may, over time, lower their conductivity. I don't find this unrealistic, but equally I don't know if the effect would be enough to be of concern.

[Ian.M]

I merely pointed out that the conductivity of cold 'galvanising' paint is likely to deteriorate quicker than nickel loaded screening paint. Anybody who doesn't think zinc oxidises in air is delusional.  Without doing a full quantitative chemical analysis and comparing with a reference sample that has been stored under inert gas, you cant tell how badly oxidised the zinc particles actually are, and unless you work for a paint research lab, you are unlikely to have the facilities (or need) for such an analysis.

The test probes are another matter - if your probes are made of brass that is so soft you have to resharpen them after only fifty measurements, you are *NEVER* going to see enough oxide buildup to cause problems. However I dont resharpen my probes daily and have had probes that did not make reliable contact probe to probe even after cleaning with IPA so in my experience oxide buildup can be a real problem.

I didn't contradict or dismiss your experimental findings, so have no idea why you are exhibiting such a severe case of butt-hurt!

[T3sl4co1l]

Look at all that delusional Corrosion happening and not only that it's going to rust the plastic! Ha Ha Ha Ha .

Well, zinc corrosion is primarily environment driven...

I suppose the overall conductivity would depend on sneak paths through layers of flat platelets.  Conductivity (and galvanizing effectiveness) will depend most critically upon how those paths oxidize.  If the binder (paint base) provides an effective oxidation barrier, then the surface will oxidize first, and the paint will last  the longest.

Tim

[T3sl4co1l]

That one looks like it might be evaporated (in vacuum), or plated (electroless, in solution), which is also a common method.

Tim

[T3sl4co1l]

Electroless can be had from Caswell Plating, probably among others.  IIRC, it's not terribly cheap, and is hazardous waste (don't pour it down the drain!).  Results may vary; plating is extremely critical of surface prep.

Vacuum would be a fair sight harder to obtain from a bottle, but some amateurs have taken it on, e.g. for telescope aluminizing.  Cool projects, but a lot of work!

Tim

[Cerebus]

For 'cold galvanising' to be effective against corrosion, the zinc particles must make electrical contact with each other and the substrate, so there is an incentive for the paint manufacturer to come up with a conductive formula even though that's not its intended use. However it will oxidise more readily than a Nickel based screening spray, loosing conductivity with time,  so you may need to over-coat it with lacquer to protect it.

I'm out rural (farming country) with a lot of steel gates and the likes out in the weather 24/7 and from practical experience i have yet to see any of these products like this "corrode" , i have seen new galvanized gates corrode just after a few months yet cleaning them up and then applying a coat brings them back to new looking , and i just looked then at a get next door that was done 3 or 4 years ago and it still looks new , practical experience .

So as far as a gadget sitting inside any concerns of corrosion is laughable imo .

I think you're misunderstanding Ian.M. He's saying that for this paint to do its job as an anti-corrosive galvanizing spray it is required perforce to be conductive and that's a useful side effect from our point of view so it makes good shielding.

The mechanism for it protecting your gates is that the zinc preferentially oxidises instead of the steel. Zinc isn't a particularly noble metal, it corrodes quite easily. Zinc granules, that you'll find in any chemistry laboratory, always have a fine coating of white zinc oxide. In galvanization it protects by corroding away over time as it donates electrons to the iron which requires a galvanic path between zinc and iron.

Ian.M's concern is that, in the shielding use,  natural surface oxidisation of the tin particles may, over time, lower their conductivity. I don't find this unrealistic, but equally I don't know if the effect would be enough to be of concern.

I'm not misunderstanding anyone , i already knew about the shielding effect and why as that is why i have used the stuff so figure that one out , i need nor require any explanation of a "why".
1st> Have you ever "in practice" been involved or seen just what happens with this type of product for real or are "you too" just basing your opinions on hypothetical theory also , that is what i accuse you of as much as you accuse me of not understanding anyone .

That stuff does not behave like you suggest on gates or whatever and out in the weather from 0 or less degrees to +45c , a cheaper brand or quality of original cold or hot dipped galv or of different quality/formula might , there is no oxidization happening as you suggest from the tins , i suggest you go and practically try it out and then you can write up a total scientific report and then dispel all hypothetical and imaginative chatter .

Look here https://www.eevblog.com/forum/repair/sharpen-those-probe-tips-(1-method)/msg949930/#msg949930 , you'll see that someone has a "issue" with corrosion or maybe even a obsession? and a hypothetical/imaginative one at that imo , and take the case in that thread of protecting the tip and never mind one is going to resharpen it in the near future and remove all the protection every time one does resharpen , so there was no hypothetical future imagination of having to do such a thing in the first place , every time .

I want a "Like" too Ha Ha Ha .

I don't see why you're getting in such a tizzy dear. I was just trying to add a little clarification. Y'know, trying to be be helpful. If you want to deny electrochemistry, feel free.

[Cerebus]

Likewise fella , if you want to deny real examples of practical examples feel free too poof .

Meh, whatever. You're clearly a lost cause...