I have an interesting dilemma but first a little background.
For seven years I had my woodshop in our one-car attached garage. It wasn't
heated or cooled and not very tight. I live in the midwest with very cold
winters and extreemly hot/humid summers. When it rained it would take on
some water from under the doors and I would have standing water until I
sopped it up. About twice a year I would put a coat of floor wax on my
tablesaw, drill press, band saw, etc. and never, never had a problem with
Now, since a recent move, I have a metal detached two-car sized building.
It has a concrete floor, 2x4 framing, and what looks to be galvanized,
corregated steel siding and roof. No drywall, no insulation, just the steel
between my tools and the outdoors. I used about 12 cans of spray foam
insulation to cut down on the breez and did a lot of caulking, it's actually
pretty tight now.
However, my tools are rusting. For a couple of months I would go out every
week or so and there would be a fine,even coat of rust on all my power tools
(all my other tools are still packed for obvious reasons). Finally I waxed
them all and covered them with cotton duck and that has kept them pretty
clean but what do you folks think is happening here? Is there a chemical
reaction with the galvanized steel? Is it condensation, like a glass of ice
water sweating? Funny thing is, the building is good and dry. And it's
been freakin' cold here for the past few months, very dry air. I'm stumped.
We can't afford to tear it down and put up something nice for a few years
yet so I'm going to put a few hundred bucks in it by covering the ceiling
with plywood and framing up some interior walls with drywall. I'll make it
all removable with screws so the materials can be re-used later.
So what do you think?
Rust on the tools indicates high humidity (a function also of
temperature.) This is an objective or empirical indicator.
Your conclusion that the building is "dry" seems to be a
subjective impression (independent of temperature.)
I.e. these two items of evidence contradict each other.
If you want to prevent rust inside the building, you should
probably heat it (after first researching how humidity
varies with temperature.)
Your old garage was partly heated by the heat coming through
the shared wall. That small amount of heat would have reduced the
humidity in the garage. You don't have that in your new location.
I would suggest that a small amount of dry heat (electric or
well vented combustion heat) would accomplish the same thing. Of
course you can buy de-humidifiers designed for cold conditions, but I
suspect they would be marginally effective in those temperatures.
In addition you may have moved to an area of higher natural
humidity. Changes in tree cover, water table etc. can make a large
difference in the humidity levels and therefore the rust.
Amen to the hitting the nail on the head.
In an unheated building tools have enough thermal mass to remain cold whe
the building heats up. The heating building drives moisture out of the
concrete on ONTO your tools.
Quick and dirty is a little heat. You might consider coating the floor to
reduce moisture rising from it.
In addition to what the other posters have said, you may have it too
tightly sealed also, therefore allowing it to trap the moisture in the
shop. Also, using an unvented heater will trap moisture in the shop.
On Fri, 20 Feb 2009 07:48:18 -0800 (PST), "Hustlin' Hank"
This would explain why metal stuff in our detached garage doesn't seem
to rust; it's unheated and quite drafty, so the ventilation must be
helping. The small shed behind it is a different story: bicycles
rust in there, but not in the garage, and I think that's because
there's less ventilation (smaller space, sandwiched between the garage
and a hillock, plus a wood (vs. concrete) floor). Same climate: very
cold winters, moderately humid summers (by Lake Ontario).
Wipe down the metal and painted parts with a kerosene rag. Make sure
there is no muriatic acid in your garage. Salty air or road salt is
bad. Sometimes putting a small light bulb under a cast iron table
will prevent rust by raising the temperature of the metal slightly.
Make sure everything is properly grounded. Etc, etc, ...
All of my gardening tools in my shed were rusting (mainly waferwood shed
with a steel roof). I installed a wind turbine. It made a huge difference.
Basically the shed was destroying itself. Now I have a Rubbermaid shed. I
installed a wind turbine. I do not have a problem with rust.
I have stood below my wind turbines during severe rainstorms and did not
detect even the slightest drizzle coming through to the inside.
Thanks everyone for your suggestions.
I have to chuckle about the "too tightly sealed" suggestion. I did my best
but still pretty drafty. Plus, no wind break here so a pretty steady 20 mph
I've tried the rust preventers, wd-40, and the old standby floor wax.
The poster that mentioned my old attached garage was "slightly" heated may
have been on to something. However, that house had a non-heated foyer
between the house and the garage. Essentially an unheated breezeway. I
also think it's interesting that that attached garage could have standing
water (36-48") puddles in it for days with 100% humidity and I never saw any
rust. We did move about ten miles from that house but pretty much same
weather conditions, no nearby creeks, we're on top of a hill, etc.
One difference is the amount of trees. Our old place was surrounded by
trees, almost completely shaded year round. Our new house has only a couple
of trees and virtually no shade (great for the telescope).
My plan right now (we don't have the money for a new garage) is to cover the
pitched ceiling with foil-backed insulation, seal the floor with that 2-part
epoxy, frame up the interior with 2x4s and add drywall, and add a vent or
two near the ceiling. I'll make it all reusable by screwing it all together
so when we do have the money....
Warm humid air coming in contact with cold metal will cause condensation and
resulting rust. Many metal roofs drip a lot on the underside because of
this. It's the same effect as morning dew.
You might want to go easy on the WD-40. I've read it corrodes metals,
particularly steel. I've switched to motor oil thinned with a little paint
thinner or naphtha. Personally I've not yet noticed any corrosion due to
the WD but I'd rather not take the chance.
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