Dew Point and Rust

[cputnam]

The dew point is that temperature at which water will condense from the air and stay liquid.  So, as long as your tools are stored where the temp is above the dew point you will not have much, if any, of a rust problem.  Putting ice in a glass on a humid day immediately illustrates the dew point - the outside of the glass is below the dew point.

One way to check the dew point is go to the Weather Underground site for your location.  For Example

The real discussion begins when your tools are at or below the dew point.  There appear to be 3 main strategies of coping:  1) - Enclosing/covering  2) - Heating  3) - Coating   All three strategies can be used in any combination.  Discussing how you deal with rust is, IMO, not especially helpful with out the context of the dew point average with which you deal.  For example, I'm in Southern California where the dew point is almost always below forecast temps.  So, for me, a light wipe down with an oil is all need to avoid rust.  Some of you may need to keep your tools enclosed, heated and wiped down with oil.

Just sayin

[MichaelMouse]

Moving the air will help keep your tools as warm as the ambient air, preventing condensation.

Use of one of those thermometer/hygrometer combinations, along with this  http://dpcalc.org/, will figure the DP for your workshop better than some weather forecaster thirty miles away.

[cputnam]

If you examine the website you will find that there are generally man very local weather stations. In my case I found one in this community - about 1/4 mile away and 100' higher. Aside from which, the website is cheaper.

My point is, not to argue measurement ways and means, but to point out what the dew point means for one's tools. The discussions on this board and others suggest that a lot of folks have not made the connection.

[MichaelMouse]

You think, perhaps, that the DP in your shop might differ from what's outdoors, or is it only mine?

Another good use for the simple instruments mentioned is available here. http://www.dryfix.net/blog/wp-content/uploads/WME.jpg

[WilliamHodge]

There is always strategy #4, Lower the Humidity. Use a dehumidifier.

[AHill]

There is always strategy #4, Lower the Humidity. Use a dehumidifier.

+1.  And not as difficult as it might seem if you store your tools in an enclosed space like a toolbox, drawer, etc.  One of those dehumidifying canisters works wonders in that case.  OTOH, I live in the desert.  As of the time of this posting, the outside temp is 78°F and the dew point is 28°F.  If you have the luxury of a dehumidifier, keeping the relative humidity below 30% will effectively eliminate rust.  That's how we stored complete divisions of equipment in Europe without having to wipe everything down with oil.