Condensation & Rust

[Doug Mason]

Unusual occurence happened in my shop last weekend. I live just north of San Francisco, and the first big rain storm of the season hit this past Saturday. The weather here is very temperate--never too cold or too hot. However, on this particular morning, I opend my garage and two hours later, every tool had a film of water over it. Heavy condensation. Everything got a light film of rust on it--from my jointer/planer to my planes. I spent an entire evening (and this coming weekend) removing the light film of rust from my tools.

My question is what is the cause of this? The temperature outside and inside of the garage is about the same (I don't use heat). It didn't happen last winter. I suppose it was a freak of coincidence--warm weather with the rain storm hitting the cooler temp inside of my garage?

[Frank Hagan]

Maybe higher humidity inside the shop that day due to the open door and the rain?

I live in Southern California near the beach, and I find the foggy days more of a problem than the rainy ones. We get a "salt fog" that will coat everything cooler than the air, like metal, with a dew. The salt in it makes it much more corrosive. Its also harder to remove because of the salt crystals. Perhaps that day the prevailing wind was from the ocean or bay instead of from overland?

[tod evans]

lack of wax caused the rust. i don`t know about the condensation...02 tod

[Roger Bell]

You might check out this discussion from the SMC archives which discusses the the relationship between the air temperature, relative humidity and the dew point.

http://www.sawmillcreek.org/showthread.php?t=19451&referrerid=2087

[Chris Barton]

What caused the condensation was the relative rapid change in air temperature in contrast to the slow change in the temperature of iron. When you shop is coldest (just prior to dawn) your iron tools have lost heat and are probably at ambient air temperature (let's say 50*). Then in the next few hours the air temperature rises to 60* and is very moist. Your tools are still very close to 50* because iron takes a long time to lose or gain heat. Because of this the water vapor in the air condenses on the exterior of the iron just like it would on a glass of iced tea on a hot summer day. The solution is to keep you tools warm (and dry).

[John Hemenway]

Doug,
I think the weather change in the last week was from cold/dry to warm(er)/wet. The tools were probably still cold, the warm(er) moist air condensed on them. Similar to cold beverage glass on a warm summer day or when I take a tool from the cold garage into the heated house.

Cures for this would be heating the shop so tools are warmer than the dew point or using a dehumidifyer in the shop (which will also warm it).
So, just how north of San Francisco are you, neighbor?

[Bruce Haugen]

I had the same exact problem a few years ago. 'Course, then, I lived in North Dakota, which is vastly colder in the winter than Calif. It was winter time, and I used a propane heater to warm the garage for a project. Apparently all the tools didn't warm up enough, and I acquired the most uniform coat of rust over anything metal. It took a very long time to clean it all.

Bruce

[Frank Hagan]

I had the same exact problem a few years ago. 'Course, then, I lived in North Dakota, which is vastly colder in the winter than Calif. It was winter time, and I used a propane heater to warm the garage for a project. Apparently all the tools didn't warm up enough, and I acquired the most uniform coat of rust over anything metal. It took a very long time to clean it all.

Bruce

Fossil fuels also add moisture to the air ... for every 100,000 btu of heat produced (just over a gallon of LP), you put 1.5 gallons of water into the air. Most portable propane heaters for garage use, even the catalytic kind, put the flue gasses, including the H2O in vapor form, into the air in the garage. The warmer air was then even more moisture laden than your normal winter air. Some propane heaters use a heat exchanger to transfer heat to the air, and all the flue products go out a flue pipe (like the Hot Dawg heaters that are popular).

[Dev Emch]

Often rust only forms when the moisture has a chance to work with oxygen. I.E. when the juice begins to dry. So at the first signs of surface rust, take a spray can of WD-40 and spray a light coat on all machined surfaces ASAP. WD-40 sometimes bubbles which is the WD-40 forcing moisture out of the poors of the iron. Thinner or turp can take this stuff off.

Then hit the iron with BoSheild and/or furniture wax. I like old fashioned wax made from turpentine and beeswax. Some forumlas also contain some plant waxes like carnuba which makes the wax a bit harder in the surface. But the combo of beeswax with turp seems to help in protecting iron and not gubbering up boards run accross the iron. It works for me.:D

[Steven Wilson]

I experience that everytime I heat my shop to comfortable in the winter (if I stay under 55F then it's fine) or when the snow finally melts in the spring. Anyhow, I've tried WD40, Boeshield, wax, etc and the only thing that works for me is to cover all of my tools and to apply a thick coat of Boeshield (spray on, don't wipe) on the cast iron (then throw a cover over it). For my planes, I spray Boeshield, store them in a plane sock, and keep them in a cabinet. I've been moving them to wooden drawers which work better with the condensation.

[Rob Will]

Without some minimun amount of heat in the building this will be a continuing problem.

[Dev Emch]

It is true about using heat. My buddy Craig uses heat in his shop in new york state. (see www.antique-engine.com (http://www.antique-engine.com%29) . According to Craig, machines should not be allowed to drop below 50 degrees when you have lots of humid air. I get away with this because, a). winters are cold and dry for us and b). I ramp the shop up from cold very slowly over several hours.

[Russ Massery]

I've found that 45 degrees (the lowest setting on my thermometer) is the lowest temperture I can get away with. Like dev said it's the big swing in humdity and temperture that will cause problems.