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I’m designing a hydrogen and corrosion sensor. A thin film changes resistance based on hydrogen concentration. Then the capacitance between two electrodes will change depending on substrate thickness (corrosion). AC analysis can be used to see a phase change in the impedance, giving capacitance changes. I have designed a basic sensor, here it is with a basic model.

But now I think an interdigitated electrodes might be better to detect the change in corrosion from the steel substrate. I’ve thrown together a basic design. I’m not sure though, has anyone got any thoughts? And what would be the best material for this electrode, I was thinking a copper? Also what would be the best way to go about modelling interdigitated electrodes, assuming lots of parallel capacitors?

Many thanks

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Are you making a corrosion sensor or a hydrogen sensor ? Corrosion sensors ( corrosion probes) ,based on metal loss have been around for over 50 years. And hydrogen is a special problem , strongly dependent on the diffusion of the hydrogen. Steel is relatively "transparent" to hydrogen above 400 F. And the solubility below 400 F depends on the steel condition and alloy. Because the surface interaction chemistry has the primary control of hydrogen entry , copper would be relatively useless for determining the hydrogen activity ( fugasity - don't get to used that word much) on a steel surface. Forgot there are hydrogen activity tools; they may be a section of steel with a concentric outer pipe ( sealed) and have just a simple pressure gage and vent valve. Periodically the pressure of hydrogen is noted and the vent opened to release the hydrogen. I may be biased as I pretty much made a career of hydrogen damage to metals.

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