Steel Corrosion due to Atmospheric Moisture
Steel Corrosion due to Atmospheric Moisture
(OP)
I'm an HVAC professional, trying to get some good information regarding room design to avoid steel corrosion. Over the years, I've heard people say that maintaining a room's relative humidity below 55% or 60% will minimize the corrosive effects of water vapor in the atmosphere. What I'd like to know is whether it's really relative humidity, or absolute humidity that's the key. I would suspect absolute humidity, but I've never seen any guidelines that refer to limits on either absolute humidity or dewpoint.
If the critical parameter is relative humidity, then raising the room temperature would help. But this obviously would not work if absolute humidity is the key.
Any info would be appreciated.
---KenRad
If the critical parameter is relative humidity, then raising the room temperature would help. But this obviously would not work if absolute humidity is the key.
Any info would be appreciated.
---KenRad





RE: Steel Corrosion due to Atmospheric Moisture
The reason relative humidity is mentioned is because indoor temperatures are maintained to a relatively small window.
You will need less than 50 % RH at 22 °C to avoid corrosion of unprotected steel (again, no reference, just my anecdotal evidence).
Regards,
Cory
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RE: Steel Corrosion due to Atmospheric Moisture
Thanks; you confirmed what I had suspected, that reducing relative humidity without removing absolute moisture would not reduce the potential for corrosion. I never thought about why relative humidity was always referred to, but your reason makes sense.
KenRad
RE: Steel Corrosion due to Atmospheric Moisture
RE: Steel Corrosion due to Atmospheric Moisture
For reference see this docs from NPL:
Atmospheric Corrosion
"Control of RH Most atmospheric corrosion can be prevented by maintaining RH below 60%."
http://
and in the Book "Corrosion" - Shreir - Chap "The atmosphere".
S.
Corrosion Protection & Corrosion Control
RE: Steel Corrosion due to Atmospheric Moisture
There is a load of information on the Bry-Air website:
http
RE: Steel Corrosion due to Atmospheric Moisture
45% seems excessively low to me, and in a southern US climate, would come with a large HVAC energy penalty. Since the number came from a company that sells dehumidification equipment, I'm skeptical.
---KenRad
RE: Steel Corrosion due to Atmospheric Moisture
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RE: Steel Corrosion due to Atmospheric Moisture