Relative Humidity and the science of Rust
Discussion
Quick question..
I believe that anything above 50% humidity in the air enables rust to form.
My question is this.. is it just the relative humidity we should be looking at or also the temperature? the reason I ask is that warm air can hold a lot more moisture so am unsure if storing a car at 20 Degrees Celcius 65% humidity is actually worse than storing it at 15 Degrees with the same relative humidity of 65%?
Although the relative humidity is the same there is actually more humidity at the higher temp.. does this not encourage more rust?
I believe that anything above 50% humidity in the air enables rust to form.
My question is this.. is it just the relative humidity we should be looking at or also the temperature? the reason I ask is that warm air can hold a lot more moisture so am unsure if storing a car at 20 Degrees Celcius 65% humidity is actually worse than storing it at 15 Degrees with the same relative humidity of 65%?
Although the relative humidity is the same there is actually more humidity at the higher temp.. does this not encourage more rust?
Have a look at this, down the page is a graph showing relative humidity in the context of car storage.
I store my R107 in one of these, it goes into winter hibernation with shiny brake discs, and emerges after the worst of the weather with shiny brake discs.
I have no relationship with this company.
https://www.autopyjama.com/permabag-uk/cars/
I store my R107 in one of these, it goes into winter hibernation with shiny brake discs, and emerges after the worst of the weather with shiny brake discs.
I have no relationship with this company.
https://www.autopyjama.com/permabag-uk/cars/
V8A*ndy said:
I'm sure the dew point may have a factor in this.
For a given relative humidity the dew point is reached more easily the lower the temperature so by that logic higher temp at same relative humidity is better for rust prevention...Is it then just the dew point that causes corrosion? or to a degree also the moisture in the air, even if it has not reached the dew point?
jackpe said:
Quick question..
I believe that anything above 50% humidity in the air enables rust to form.
My question is this.. is it just the relative humidity we should be looking at or also the temperature? the reason I ask is that warm air can hold a lot more moisture so am unsure if storing a car at 20 Degrees Celcius 65% humidity is actually worse than storing it at 15 Degrees with the same relative humidity of 65%?
Although the relative humidity is the same there is actually more humidity at the higher temp.. does this not encourage more rust?
For a given relative humidity, the warmer air will hold much more water and also iirc chemical reactions are faster in warmer temperatures so a double negative whammy.I believe that anything above 50% humidity in the air enables rust to form.
My question is this.. is it just the relative humidity we should be looking at or also the temperature? the reason I ask is that warm air can hold a lot more moisture so am unsure if storing a car at 20 Degrees Celcius 65% humidity is actually worse than storing it at 15 Degrees with the same relative humidity of 65%?
Although the relative humidity is the same there is actually more humidity at the higher temp.. does this not encourage more rust?
renaultgeek said:
also has to do with chlorides in the air, so if you live near the coast you're more likely to rust up.
It would happen with any salts - rust is an electrochemical phenomenon, and anything that can transfer charge (essentially, electrons) allows oxidation to occur. For example, it is often not wise to wash a car regularly with fairy liquid - the surfactants are charged (anionic) and promote corrosion of steel. spitsfire said:
The best solution is probably to avoid owning anything British or Italian.
and the best way to avoid hangovers is not to drink... and the best way to avoid getting your girlfriend pregnant is to never have sex... but it could all lead to a very dull life.
Enjoy your cars throughout the winter and when they rust, restore them (again)!
S..
spitsfire said:
The best solution is probably to avoid owning anything British or Italian.
Yes, some Italian cars (Lancia Beta comes to mind) did suffer very badly with rust in the 1970s and 1980s, and all cars driven in British winter conditions suffer greatly from rust due to the use of salt on the roads!!Owning something Italian (71 Giulia GTJunior), and reading this thread I thought I ought to get a humidity meter.
It arrived today, sat it on the car in the garage; 9 degrees at 85% humidity.
So according to the previous link, it's just about OK, but defiantly something I need to keep an eye on.
The problem I have is there is an open drain that runs through the garage from all the rain water on the driveway, to the river behind the garage.
Last year I closed all the windows on the car, then by spring there was a fine layer of mould over the interior, so this year it's stored with all the windows open.
It arrived today, sat it on the car in the garage; 9 degrees at 85% humidity.
So according to the previous link, it's just about OK, but defiantly something I need to keep an eye on.
The problem I have is there is an open drain that runs through the garage from all the rain water on the driveway, to the river behind the garage.
Last year I closed all the windows on the car, then by spring there was a fine layer of mould over the interior, so this year it's stored with all the windows open.
jamieandthemagic said:
Owning something Italian (71 Giulia GTJunior), and reading this thread I thought I ought to get a humidity meter.
It arrived today, sat it on the car in the garage; 9 degrees at 85% humidity.
So according to the previous link, it's just about OK, but defiantly something I need to keep an eye on.
The problem I have is there is an open drain that runs through the garage from all the rain water on the driveway, to the river behind the garage.
Last year I closed all the windows on the car, then by spring there was a fine layer of mould over the interior, so this year it's stored with all the windows open.
85% not good enough IMO.It arrived today, sat it on the car in the garage; 9 degrees at 85% humidity.
So according to the previous link, it's just about OK, but defiantly something I need to keep an eye on.
The problem I have is there is an open drain that runs through the garage from all the rain water on the driveway, to the river behind the garage.
Last year I closed all the windows on the car, then by spring there was a fine layer of mould over the interior, so this year it's stored with all the windows open.
Needs to be less than 60% to be below steep part of curve (where corrosion starts to take off). Mildew as good a sign as any that too damp! See point 4 at this link:
http://www.rentdh.com/about-dh-tech/technology-rev...
PS Permabag, Carcoon may accept higher RH at low temps but that is because they don't control RH (unless you use dehumififier inside one). But professional stores generally go for 55%.
My solution to a damp garage like yours - Carcoon Veloce (drive in drive out) with small dessicant dehumidifier inside.
And yes I do drive it in the rain!
Edited by drmark on Saturday 21st December 20:23
Also need to take into account the negative effect of low humidity on leather if you have leather seats and elsewhere.
See : https://www.leather-dictionary.com/index.php/Stora...
Looks like about 60% relative humidity might be a compromise between steel and leather?
See : https://www.leather-dictionary.com/index.php/Stora...
Looks like about 60% relative humidity might be a compromise between steel and leather?
mastrati said:
Also need to take into account the negative effect of low humidity on leather if you have leather seats and elsewhere.
See : https://www.leather-dictionary.com/index.php/Stora...
Looks like about 60% relative humidity might be a compromise between steel and leather?
The OP asked his ‘quick question’ seven years ago. His car has probably rusted away by now. See : https://www.leather-dictionary.com/index.php/Stora...
Looks like about 60% relative humidity might be a compromise between steel and leather?
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