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Author: Subject: Need some help on how to calculate the surface area of expanded mesh.
mysteriusbhoice
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[*] posted on 19-7-2021 at 08:19
Need some help on how to calculate the surface area of expanded mesh.


I am working on a coating process with a friend for PbO2 on titanium without MMO and so far the tests on the strips are succesful.
These electrodes use a relatively cheap conductive undercoat using my technique which allows to plate any metal directly onto Ti without nickel by simply adding HF 3% by wt in the plating bath which sounds cursed but it works.

The conundrum now is that some titanium meshes are the diamond expanded mesh type and the PbO2 coating process the 1st layer has a very narrow current density for plating. Too much and it will produce a porous rough mass which is undesirable. I have found the perfect operating current density on plate electrodes for all the plating baths and times but I need to know a good way to get a near exact total surface area of an expanded mesh electrode.

The issues are they come in different sizes and the sellers sometimes dont give any info on the surface area of the mesh. I wonder if theres a formula to get the true surface area of the metal part of the mesh.

Video of electrode plating process and short test below.
https://youtu.be/5WlzECMoqQk

[Edited on 20-7-2021 by mysteriusbhoice]
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Twospoons
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[*] posted on 19-7-2021 at 14:27


Might be best to measure a sample.
Starting with flat plate as a reference, and a piece of mesh to test:
weigh them dry, then dunk both into a detergent solution. Remove, shake off the drips and weigh them wet. Assuming the liquid film thickness will be similar on both pieces then the weight of the liquid film should be proportional to the surface area, so you should be able to get a close estimate of the mesh area using the flat sheet as a reference. Does that make sense?

Or you could anodise both test pieces and compare capacitance with a liquid electrolyte as the counter electrode. But you'd need the anodising to be identical.




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Johnny Cappone
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[*] posted on 19-7-2021 at 15:53


Unfortunately I can't provide a reference, but a few years ago, at a pyrotechnics forum in which I participated, calculations were made and it was concluded that the total area of ​​the "diamond-shaped" titanium meshes was simply... the area total, as if the part were a solid sheet.
The area of ​​the recesses would compensate for the empty spaces. Or maybe I saw it right here on SM and I'm going crazy. So many data, so many threads, my mind is no longer the same.




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WGTR
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[*] posted on 19-7-2021 at 16:41


Well, if we assume that the mesh is simply flat sheet that is expanded, I would start by obtaining an accurate thickness measurement and weight of a given sample. Using these values I would then back-calculate the area of an un-expanded sheet of the same material and thickness. Then I would count the number of openings in the sample and add the area from the edges for each opening. That should get you close, I think. Beyond that, plan on running several tests at different current densities to obtain an adjustment factor for your particular type of expanded material.



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mysteriusbhoice
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[*] posted on 19-7-2021 at 23:27


Quote: Originally posted by Johnny Cappone  
Unfortunately I can't provide a reference, but a few years ago, at a pyrotechnics forum in which I participated, calculations were made and it was concluded that the total area of ​​the "diamond-shaped" titanium meshes was simply... the area total, as if the part were a solid sheet.
The area of ​​the recesses would compensate for the empty spaces. Or maybe I saw it right here on SM and I'm going crazy. So many data, so many threads, my mind is no longer the same.


That is only true for forward expanded mesh but not flat expanded mesh where its then flattened and in that case this is no longer true.
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rockyit98
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[*] posted on 20-7-2021 at 02:54


using capacitive testing. can get pretty accurate.



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mysteriusbhoice
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[*] posted on 22-7-2021 at 01:27


I have come up with my own formula since posting this
defining measurements:
1. measure width and length of each diamond hole. (l, w)
2. count how many holes are in each row and how many rows of holes are there ( be aware if its staggered) (nlh, nwh)
3. measure length and width of assumed plate electrode. (L, W)
4. thickness of mesh t,
Calculations:
1. perimeter of each hole p = 2x(l+w)
2. number of holes n = nlh x nwh
3. Surface area of inner sides of hole SAi = pxnxt
4. Surface area of flat plate SAp = 2x(LxW)
5. substractive area of spacing of holes SAs = [2x(lxw)]xn
6. Real surface area SA = SAp - SAs + Sai

The calculator works for FLAT diamond mesh only not forward as that has greater surface area as a flat plate of the same dimensions.

Attachment: Mesh calculator.xlsx (12kB)
This file has been downloaded 32 times

[Edited on 22-7-2021 by mysteriusbhoice]
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