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newbie here.

I'm asking a question that is related to hygrometer calibration.

I read in sensitive digital hygrometers, it is stated that saltwater test should not be used to calibrate as it will damage the electronics (resistor?) that is used for measurement.

But how does this ring true? Saltwater does not evaporate, or do they?

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  • $\begingroup$ Salt water can corrode metals. If your instrument says not to use with saltwater, assume the manufacturer knows the limitations of the device. $\endgroup$
    – MaxW
    Mar 6, 2017 at 13:22
  • $\begingroup$ @MaxW I think the question here is why saltwater would damage the hygrometer if it only measures humidity in the air with the presumption that salt doesnt evaporate with the water which evaporates to build up the humidity? $\endgroup$
    – user37142
    Mar 6, 2017 at 13:44
  • $\begingroup$ I was assuming that "saltwater test to calibrate" somehow wet the device with saltwater to calibrate it. // It could mean measurements over salt water like on a boat. The sea spray would dry tiny droplets of salt water, so the air would have some salt particles in it. In any case the the manufacturer should have stipulated the limitations of the device. $\endgroup$
    – MaxW
    Mar 6, 2017 at 14:18

1 Answer 1

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Salt water is an excellent electrolyte, and will accelerate galvanic corrosion reaction between two different metals especially in oxygen rich environments (including dissolved oxygen in water). This may create metal oxide deposits on circuits. The longer the exposure time the more corrosion can occur.

If your device is on, that is, there are circuits with electricity flowing, clearly adding a salt water could also short circuit your device as well.

As to whether any of the above results in irreversible damage is hard to say with certainty as some devices have been dried out and appear to function at least following exposure to common tap water.

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